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VAN NOSTRAND'S
ECLECTIC
Engineering Magazine
VOLUME XIX.
JULY-DECEMBER
1878.
NEW Y O R K :
D. VAN NOSTRAND, PUBLISHER.
23 Murray Street and 2? Warren Street (up stairs).
18 7 8.
3^, •• ■•/
A
V5
CONTENTS.
VOL. XIX.
Page.
Accidents to bridges 534
Accidents, prevention of 526
Accurate navigation 47
Action of brakes 251
Action of railway brakes 339
Addition to the British navy 93
Aeronautics 439
Air, compressed 466, 4S1
Air duct for mines 192
Air vs. water 424
Altenbnrg tunnel 4T4
American Institute of Mining En-
gineers 88
American Society of Civil Engi-
neers 88, 185,317, 471
American Society of Civil Engi-
neers 563
Ammonia, distribution of 374
Ammunition expenditure 568
Analyses of Russian iron 279
Ancient land survey 429
Architect, studies of 419
Architectural cements 498
Armor-plate tests 190
Arnold Hague 458
Artificial fuel 544
Artificial marble 324
Artificial stone 96
Atmosphere 135
Aubois canal-lock. 85
Belgian Railway Co 2S0
Birmingham wire gauge 564
Buster steel 21
Boiler explosions 119
Boilers, use of zinc in 561
Book Notices :—
Adams, Charles F., Jr. Rail-
roads—Their Origin and
Problems 383
Bilgram, Hugo, M.E. Slide-
Valve Gears 382
Bourne, John, C.E. Modern
Engines 570
Brown, J. Croumbie. Plan-
tations on the Sand Wastes
of France— Journal of For-
estry 94
Cain, Prof. Wm., A M., C.E.
Maxi i.um Stresses in
Framed Bridges 383
Caldwell, Geo. C, S.B., Ph.D.
and A. A. Breneman, S.B.
Chemical Practice 382
Carpenter, F. De Y. Geo-
graphical Surveying. . . 287, 478
Comstock, Gen. C. B. Survey
of the Northern and North-
western Lakes, &c 570
Du Bois, A. Jay, C.E., Ph.D.
Graphical Statics . . ....... 478
Du Bois, A. Jay. Graphical
Statics 571
Du Moncel, Th. Electricite. 191
Fontaine, H. Electric Light-
ing 384
Forrest, James, A. J. C. E.
Proceedings of the Institu-
tion of Civil Engineers 569
Fourier, Joseph. Theory of
Heat 477
Frankland, E..D.C.L., F.R.S.
Researches in Chemistry.. 569
Handbook of Inspectors of
Nuisances 384
Hartley, W. Noel, F.R.S.E.,
F.S.C. Water, Air and Dis-
infectants 191
Huntington, W. S. Road
Master's Assistant 95
Institution of civil engineers 384
Jordan, D. S., Ph.D.
of Vertebrate? 383
King, U.S.N. War Ships of
P^urope 95
Kirkmau, M. M. Railway
Service 2S7
Latham, B., F.G.S., C.E.
Sanitary Engineering 384
Loring, A. E. Electro Tele-
graph 477
MacDonald, .lames. Ameri-
can Agriculture 3S4
Mammene, E. J. La Fabrica-
tion du Sucre 95
Marey, E. J. La Methode
Graphique dans la Sciences
Experimentales 95
Millar, J. B., B.E. Descript-
ive Geometry 190
Nicolls, W. J., C.E. Railway
Builder 191
Pechar, J. Coal and Iron — 477
Prang's Alphabets 476
Proceedings of the Institution
of Civil Engineers 95, 287
Page. Page.
Manual ; Canal-lock, Aubois 85
Cast steel, silicon in 550
Cause of blisters on " blister
steel" 21
Causes of accidents to bridges. . . 534
Cements, architectural 498
Changes in the earth's magnetism. 230
Cheap railway 186
Chilltd cast iron wheels 566
Chromium in alloys 565
Circular curves for railways 10
Civil engineer, studies of 419
Cleopatra's needle 263
Coal mines, ventilation of 369
Co-efficient of friction 519
Collapsing boat. 94
Compass in mining surveys 259
Composite armor-plates 286
Compre.-sed air 466, 431
Congress on civil engineering 377
Conservancy of rivers and streams 345
Continuous girders 553
Conversion of motion 433
Cord and pulley 395
Cotton powder or tonite 321
Report of Survey of Northern
Lakes 570 j Dangerous shunting operations.. 473
Riddell, Robert. The Artisan 569 Deducing formulae 360
Sadtler, S. P., A.M., Ph.D. ] Deep boring 310
Chemical Experimentation . 383 j Determination of Rocks 399
Different qualities of iron and
steel 564
Discharge of rainfall 22
Discharge of sewage 54S
Discussion on continuous girders 553
Distribution of ammonia 374
Don Pedro Segundo Railway 9
Drainage in Bombay 418
Drainage of Glasgow 112
Dynamometer 277
Dynamometer, new 560
Earth boring 310
Earth's magnetism 121, 230
Earthquake country, structuresin 271
Earthquakes and buildings 248
East India Railway Co 91
Education in France 2S7
Effect of river improvement 541
Elasticity of American wood 8
Electric fuse and heavy cannon.
Signal Office Report for 1877. 3S3 >
Skertchley, B. J., F. G. S.
Outline of Physiography. . . 570 i
Smith, Edward, M.D., F.R.S.
Manual for Health Officers. 3S3
Spretson, N. E. Treatise on
Casting 477 '
Stanley, VV\ F. Mathematical
Instruments 569 :
Thompson, W. P., C.E. Pat-
ent Law 478 j
Thurston, Robert H., A.M.,
C.E. Growth of the Steam
Engine 477
Tidy, Dr. M. Modern Chem-
istry 569 ;
Treatise on Files and Rasps. 3S3
Trousset, Jules. Histoire de
la Marine . 569
Voillet-le-Duc, E. Le Massif
du Mont Blanc 191 I Electricity for transmitting mo-
Warren, Maj.-Gen. G. K.
Bridging the Mississippi
River 570
Westcott, T. Life of John
Fitch 383
Whitworth, Jos. Whitworth
Papers 287
Wilson, Robert, A. J. C. E.
Boiler and Factory Chim-
neys 95
Wright, C. R. A. Metals .... 191
Wurtz, Ad. Dictionnaire du
Chimie 570
Boring on the Continent 310
tion 133
Engine economy 42
Engineering, sanitary 308
Engineers Club of Philadel-
phia 83,471,563
Engineers, work of 183
Engines, air vs. water 424
English railways 566
Error in leveling 287
Experiments on he ghts of jets. . . 524
Experiments on railway brakes. . 519
Experiments on ship models 432
Explosion of a western river
steamer 206
Brake as a dynamometer 277 | Explosions, boiler 119
Brakes, action of 251, 339 Extension of the railway system. 473
Brakes, railway 519 '
Breech-loaders 93 I
Breech-loading artillery 94 '
Bricks and brick making 353 j
Bridges, framed 71, 146
Bridges, iron 134
Bridging the Mississippi and Mis-
souri 281
Britannia bridge 256
Bronze age 502
Builders, railway 266
Building in India 240
Building material 254
Buildings and earthquakes 248
Fire engines 480
Fire-resisting flooring 192
Flow of solids 326
Food vs. fuel 245
Formul e, method of deducing.. 360
Foster testimonial fund 288
Foundations for bridges 282
Four dimensions 83
Framed bridges, stresses in 71, 146
Friction between a cord and pul-
ley 395
Friction, co-efficient of 519
Fuel, artificial 544
1]
CONTENTS.
Page.
Fuel, gas as 39
Fuel in India 280
Garrett torpedo boat 381
Gas as fuel 39
Gatling guns 283
Gearing, laying out 312
Geographical surveying 52, 163
Geological relations of atmos-
phere 1 35
Girder, continuous 553
Girders, strain of 115
Girders, strength of 134
Glasgow, drainage of 112
Glass cloth 479
Glass tumblers . , 41
Glycerine arrests decomposition. 438
Graphical statics 1, 97, 234
Great engineering feat 187
Gun carriages 93
Harbor improvements 193
Hardening wood pulleys 114
Health, public 183
Heat value of fuel 479
Heavy ordnance 189
Height of jets 479
Heights of jets, experiments on. . 524
Highways of Paris 567
Hoopes' & Townsend's Works.. 377
Horse vs. Steam engine 245
Hydrology of the Mississippi 211
Ice in Bombay 287
Importance of geological knowl-
edge to engineers 480
Improvements of Charleston (S.
C.) harbor 193
Improvements of rivers 541
India, building in 240
Influence of the moon on the
earth's magnetism 121 |
Institute of Mechanical Engi-
neers S9, 279
Internal stress in graphical sta-
tics 1,97, 234
Iron and steel 459
Iron and steel, different qualities. 564
Iron and steel at Philadelphia... 279
Iron and steel for ships 105
Iron as a building material 254
Iron bridges 134
Iron, overstrain in 534
Iron pillars 360
Italian iron-clad 284
Japan,protection of river banks in 129
Jetties in Charleston (S. C.)
harbor 193
Jets, experiments on 524
Kutter's formula 390
Land survey, ancient 429
Larger wheels for cars 565
Lattice girders, strain of , . 115
Laying out gearing 312
Loading of heavy guns 284
London, provision for rain fall in 22
Long span railway bridges 92
Loss of a locomotive in quick-
sand 288
Low jetties 193
Macadamized roads 568
Magnetic needle 413
Magnetism, earth's 121, 230
Manufacture of artificial fuel 544
xWanufacture of iron and steel . . 459
Manufacture of materials in India 240
Manufacture of steel 378
Marble, artificial 324
Mathematical science 402
Maximum stress in framed
bridges ..71, 146
Measuring the strain of lattice
girders 115
Mechanical conversion of motion 433
Metallurgy, ori gin of 502
Mines, ventilation of 369
Mining surveys, compass in 259
Mississippi, hydrology of 211
Momentum and vis viva 229
Monster ordnance 188
Page.
Mont Cenis tunnel 396
Moon's influence on the earth's
magnetism 121
Moose mine of Colorado 82
Mosandria, a new metal 359
Most ancient land survey 429
Motion, transmission of 133
Narrow gauge in Guatamala 473
Navigation, accurate 47
Needle, Cleopatra's 263
Needle, magnetic 413
New dynamometer 560
New explosive 284
New field gun 284
Newfoundland railway 567
New motor for Tram-cars 565
Orenburg and Central Asia 379
Origin ot metallurgy 502
Overstrain in iron 534
Palliser on projectiles 569
Paris exhibition, iron and steel at 459
Paris highways 567
Paris observatory 288
Paris, sewerage system of 124
Paris, street cleansing in 103
Pig iron of the United States ... 91
Pioneer and military railways. . 91
Planet Vulcan 479
Plates, steel 268
Population of the earth 572
Porphyry 399
Powder, cotton 321
Power, transmission 466, 481
Preservation of iron 90
Preservation of iron surfaces 36S
Prevention of railway accidents. 526
Programme of studies 419
Projectiles 96
Properties of iron and mild steel. 472
Proposed removal of Smith's
Is and 385
Protection from lightning 253
Protection of river banks in
Japan 129
Provision for rain fall in London 22
Public health 183
Public works in France 283
Pulley and cord 395
Purification of water 28
Queensland railways 474
Quick steaming 285
Railroads of the U. S. in 1877. ... 280
Railway accidents 474
Railway accidents 526
Railway across Newfoundland. . . 567
Railway brakes 339
Railway brakes, experiments on. 519
Railway builders 266
Railway empioves in India 473
Railway half-finished 379
Railway ticket system 566
Railways, circular curves for 10
Railways in Russia 566
Railways of the United Kingdom 566
Railway wheels 565
Rainfall in London 22
Rectangles ir scribed in a given
rectangle ., 532
Removal of Smith's Island 385
Rensselaer Polytechnic Institute. 384
Resistance of ships 432
River banks, protection of in
Japan 129
River improvement works 541
Rivers in Brazil 282
River, Mississippi 211
Rivers and streams 345
River steamer, explosion of 206
RiverThames 342
Riveted joints 268
Rocks, determination of 399
Rolling stock 266
Russian steamers 475
Sanitary engineering 308
Science, mathematical 402
Secular variations 413
Page.
Sewage, discharge cf 548
Sewage system of Paris 124
Sharpening files 368
Shell penetration 284
Ships models, experiments on 432
Ships, steel 274
Siemens-Martin metal 279
Silicon, influence on cast steel. .. 550
Six-inch breech-loader 190
Smith's Island, removal of . . . 3S5
Societe des Ingenieurs 317
Solids, flow of 326
Space of four dimensions 83
Stamp mill in Venezuela 390
Steam boiler explosions .... 119
Steam engine economy 42
Steamer, explosion of 20ft
Steamship accidents 526
Steam steering gear 475
Steam tramway engines 92
Steam vs. horsepower 245
Steel at the Paris exhibition 471
Steel, blisters on 21
Steel for ship-building 105
Steel for structural purposes 472
Steel, manufacture of 459
Steel plates 268
Steel ships 274
Steel vs.Iron 185
Steering of screw steamers 475
St. Gothard 379
St. Gothard railway 280, 474
Storm flood 96
Streams, conservancy of 345
Street cleansing in Paris 103
Strength of girders 134
Stresses in framed bridges — 71, 146
Stress, internal 1, 97, 284
Structures in earthquake regions. 271
Studies of the architect and en-
gineer 419
Survey, ancient 429
Surveying, geographical 52, 163
Survey of silver mines 325
Surveys, mining 259
Sutro tunnel 282
System of drainage in Glasgow.. 112
Telephone in India 192
Telephones on the Central Pacific 233
Telescopic artillery sights 568
Temperature of the head 262
Testing of collapsing boats 432
Tests for diamonds 162
Thames 342
Thames torpedoes 94
Tide calculating machine 192
Tonite 321
Torpedo cases 93
Torpedo defenses 96
Torpedo depot ships 475
To pedo warfare 285
Tramways 318
Transmission of motion 133
Transmission of power 466, 481
Transportation car 186
Tunnel, Mont Cenis 396
Underground telegraph 96
Uniformity in sanitary engineer-
ing... 308
University College, London 338
Variations of the needle 413
Venezuela, stamp mill in 390
Ventilation of coalmines 369
Ventilation of the Mont Cenis
tunnel 396
Vibration of wood 8
Victorian railways 379
Vis viva 229
Water engines vs. air engines. .. 424
Water, purification of 28
Water supply to a stamp mill 390
Wheels, chilled cast iron 566
Wheels, railway 565
Wire rope conveyance 567
Wire tramway 282
Wood, elasticity of 8
Wrought iron pillars 360
Zinc, use of in steam boilers 561
VAN NOSTRAND'S
ECLECTIC
ENGINEERING MAGAZINE.
NO. CXV -JULY, 1878 -VOL. XIX.
THE THEORY OF INTERNAL STRESS IN GRAPHICAL
STATICS.
By HENRY T. EDDY, C. E., Ph. D., University of Cincinnati.
Written for Van Nostrand's Magazine.
I.
Stress includes all action and reaction
of bodies and parts of bodies by attrac-
tion of gravitation, cohesion, electric
repulsion, contact, etc., viewed espe-
cially as distributed among the particles
composing the body or bodies. Since
action and reaction are necessarily equal,
stress is included under the head of
Statics, and it may be defined to be the
equilibrium of distributed forces.
Internal stress may be defined as the
action and reaction of molecular forces.
Its treatment by analytic methods is
necessarily encumbered by a mass of
formulae which is perplexing to any ex-
cept an expert mathematician. It is
necessarily so encumbered, because the
treatment consists in a comparison of
the stresses acting upon planes in vari-
ous directions, and such a comparison
involves transformation of quadratic
functions of two or three variables, so
that the final expressions contain such
a tedious array of direction cosines that
even the mathematician dislikes to em-
ploy them.
Now, since the whole difficulty really
lies in the . unsuitability of Cartesian co-
ordinates for expressing relations which
are dependent upon the parallelogram of
Vol. XIX.— No. 1—1
forces, and does not lie in the relations
themselves, which are quite simple, and,
which no doubt, can be made to appear
so in quaternion or other suitable nota-
tion; it has been thought by the writer
that a presentation of the subject from a
graphical stand point would put the
entire investigation within the reach of
any one who might wish to understand
it, and would also be of assistance to
those who might wish to read the analyt-
ic investigation.
The treatment consists of two princi-
pal parts: in the first part the inherent
properties of stress are set forth and
proved by a general line of reasoning
which entirely avoids analysis, and
which, it is hoped, will make them well
understood; the second part deals with
the problems which arise in treating
stress. These problems are solved
graphically, and if analytic expressions
are given for these solutions, such ex-
pressions will result from elementary
considerations appearing in the graphi-
cal solutions. The constructions by
which the solutions are obtained are
many of them taken from the works of
the late Professor Rankine, who em-
ployed them principally as illustrations,
VAN NOSTRAND'S ENGINEERING MAGAZINE.
and as auxiliary to his analytic investi-
gations.
It is thus proposed to render the
treatment of stress exclusively graphical,
and by so doing to add a branch to the
science of Graphical Statics, which has
not heretofore been recognized as sus-
ceptible of graphical treatment. It
seems unnecessary to add a word as to
the importance, not to say necessity, to
the engineer of a knowledge of the
theory of combined internal stress, since
all correct designing presupposes such
knowledge.
Stress on a Plane. — " If a body be
conceived to be divided into two parts
by an ideal plane traversing it in any
direction, the force exerted between
those two parts at the plane of division
is an internal stress." — Rankine.
A State op Internal Stress is such
a state that an internal stress is or may
be exerted upon every plane passing
through a point at which such a state
exists.
It is assumed as a physical axiom that
the stress upon an ideal plane of divi-
sion which traverses any given point of
a body, cannot change suddenly, either
as to direction or magnitude, while that
plane is gradually turned in any way
about the given point. It is also as-
sumed as axiomatic that the stress at
any point upon a moving plane of divi-
sion which undergoes no sudden changes
of motion, cannot change suddenly
either as to direction of amount. A
sudden variation can only take place at
a surface where there is a change of
material.
GENERAL PROPERTIES OF PLANE STRESS.
We shall call that stress a plane stress
which is parallel to a plane; e.g., let the
plane of the paper be this plane and let
the stress acting upon every ideal plane
which is at right angles to the plane of
the paper be parallel to the plane of the
paper, then is such a stress a plane
stress.
The obliquity of a stress is the angle
included between the direction of the
stress and a line perpendicular to the
ideal plane it acts upon. This last
plane we shall for brevity call the plane
of action of the stress, and any line
perpendicular to it, its normal. In plane
stress, the planes of action are shown by
their traces on the plane of the paper,
and then their normals, as well as their
directions, the magnitudes of the stresses,
and their obliquities are correctly rep-
resented by lines in the plane of the
paper.
The definition of stress which has
been given is equivalent to the state-
ment that stress is force distributed over
an area in such wise as to be in equili-
brium.
In order to measure stress it is neces-
sary to express its amount per unit of
area: this is called the intensity of the
stress.
Stress, like force, can be resolved into
components. An oblique stress can be
resolved into a component perpendicular
to its plane of action called the normal
component, and a component along the
plane called the tangential component or
shear.
When the obliquity is zero, the entire
stress is normal stress, and may be either
a compression or a tension, i.e., a thrust
or a pull. When the obliquity is +90°,
the stress consists entirely of a tangen-
tial stress or shear. If a compression be
considered as a positive normal stress, it
is possible to consider a normal tension
as a stress whose obliquity is +180°,
and the c bliquities of two shears having
opposite signs, also differ by 180°.
Fig.l
Conjugate Stresses. — If in Fig. 1
any state of stress whatever exists at o,
and xx be the direction of the stress on a
plane of action whose trace is yy, then is
yy the direction of the stress at o on the
plane whose trace is xx. Stresses so
related are said to be conjugate stresses.
For consider the effect of the stress
upon a small prism of the body of which
axa^aK is a right section. If the stress
is uniform that acting upon «x«4 is equal
and opposed to that acting upon a2as,
and therefore the stress upon these
faces of the prism are a pair of forces in
equilibrium. Again, the stresses upon
INTERNAL STRESS IN GRAPHICAL STATICS.
3
the four faces form a system of forces
which are in equilibrium, because the
prism is unmoved by the forces acting
upon it. But when a system of forces
in equilibrium is removed from a sys-
tem in equilibrium, the remaining forces
are in equilibrium. Therefore the re-
moval of the pair of stresses in equili-
brium acting upon axa4 and a2as from
the system of stresses acting upon the
four faces, which are also in equilibrium,
leaves the stresses upon axa2 and a3a4 in
equilibrium. But if the stress is uni-
form, the stresses on axa2 and a%ak must
be parallel to yy, as otherwise a couple
must result from these equal but not
directly opposed stresses, which is in-
consistent with equilibrium.
This proves the fact of conjugate
stresses when the state of stress is uni-
form: in case it varies, the prism can be
taken so small that the stress is sensibly
uniform in the space occupied by it, and
the proposition is true for varying stress
in case the prism be indefinitely dimin-
ished, as may always be done.
Fiff. 2 /
JL
Tangential Stresses. — If in Fig. 2
the stress at o on the plane xx is in the
direction xx, i.e. the stress at o on xx
consists of a shear only; then there
necessarily exists some other plane
through o, as yy, on which the stress
consists of a shear only, and the shear
upon each of the planes xx and yy is of
the same intensity, but of opposite sign.
For let a plane which initially coin-
cides with xx revolve continuously
through 180° about o, until it again co-
incides with xx, the obliquity of the
stress upon this revolving plane has
changed gradually during the revolution
through an angle of 360°, as we shall
show.
Since the obliquity is the same in its
final as in its initial position, the total
change of obliquity during the revolu-
tion is 0° or some multiple of 360°. It
cannot be 0°, for suppose the shear to be
due to a couple of forces parallel to xx,
having a positive moment; then if the
plane be slightly revolved from its
initial position in a plus direction, the
stress upon it has a small normal com-
ponent which would be of opposite sign
if the pair of forces which cause it were
reversed or changed in sign; or, what is
equivalent to that, the sign of the small
normal component would be reversed if
the plane be slightly revolved from its
initial position in a minus direction.
Hence the plane xx, on which the stress
is a shear alone, separates those planes
through o on which the obliquity of the
stress is greater than 90° from those on
which it is less than 90°, i.e., those hav-
ing a plus normal component from those
having a minus normal component.
Since in revolving through +180° the
plane must coincide, before it reaches its
final position, with a plane which has
made a slight minus rotation, it is evi-
dent that the sign of the normal com-
ponent changes at least once during a
revolution of 180°. But a quantity can
change sign only at zero or infinity, and
since an infinite normal component is
inadmissible, the normal component
must vanish at least once during the
proposed revolution. Hence the obliq-
uity is changed by 360° or some multi-
ple of 360° while the plane revolves 180°.
In fact the normal component vanishes
but once, and the obliquity changes by
once 360° only, during the revolution.
It is not in every state of stress that
there is a plane on which there is no
stress except shear, but, as just shown,
when there is one such plane xx there is
necessarily another yy, and all planes
through o and cutting the angles in
which are hx and b3 have normal com-
ponents of opposite sign from planes
through o and cutting the angles in
which are 52 and b4.
To show that the intensity of
the shear on xx is the same as
that on yy, consider a prism one unit
long and having the indefinitely small
right section byb2bzbA. Let the area of
its upper or lower face be a^bjb^, that
of its right or left face be a2 — b2bz, then
als1 and aus2 are the total stresses on
these respective faces if *j and s2 are the
intensities of the respective shears per
square unit. Let the angle xoy—i, then
a,s, . a„ sin. i
van nostrand's engineering magazine.
is the moment of the stresses on the
upper and lower faces of the prism, and
a2s2 . ax sin. i
is the moment of the stresses on the
right and left faces; but since the prism
is unmoved these moments are equal.
These stresses are at once seen to be
of opposite sign.
Fig. 3
V
A
"* X
0
x *
Y
V
Tangential Components. — In Fig. 3
if xx and yy are any two planes at right
angles to each other, then the intensity
at o of the tangential component of the
stress upon the plane xx is necessarily
the same as that upon the plane yy, but
these components are of opposite sign.
For the normal components acting
upon the opposite faces of a right prism
are .necessarily in equilibrium, and by a
demonstration precisely like that just
employed in connection with Fig. 2 it is
seen that for equilibrium it is necessary
and sufficient that the intensity of the tan-
gential component on xx be numerically
equal to that on yy, but of opposite
sign.
State of Stress. — In a state of plane
stress, the state at any point, as o, is
completely defined, so that the intensity
and obliquity of the stress on any plane
traversing o can be determined, when
the intensity and obliquity of the stress
on any two given planes traversing that
point are known.
For suppose in Fig. 4 that the intensi-
ty and obliquity of the stress on the
given planes xx and yy are known, to
find that on any plane x'x' draw
mn || x'x' then the indefinitely small
prism one unit in length whose right
section is mno, is held in equilibrium by
the forces acting upon its three faces.
The forces acting upon the faces om and
on are known in direction from the
obliquities of the stresses, and, if px and
py are the respective intensities of the
known stresses, then the forces are
om.px and on.py respectively. The re-
sultant of these forces and the reaction
which holds it in equilibrium, together
constitute the stress acting on the face
mn: this resultant divided by mn is the
intensity of the stress on mn and its
direction is that of the stress on mn or
x x .
Fig. 4
It should be noticed that the stress at
o on two planes as xx and yy cannot be
assumed at random, for such assumption
would in general be inconsistent with
the properties which we have shown
every state of stress to possess. For in-
stance we are not at liberty to assume
the obliquities and intensities of the
stresses on xx and yy such that when
we compute these quantities for any
plane x'x' and another plane y'y' at
right angles to x'x' in the manner just
indicated, it shall then appear that the
tangential components are of unequal
intensity or of the same sign. Or, again,
we are not at liberty to so assume these
stresses as to violate the principle of con-
jugate stresses.
But in case the stresses assumed are
conjugate, or consist of a pair of shears
of equal intensity and different sign on
any pair of planes, or in case any stresses
are assumed on a pair of planes at right
angles such that their tangential compo-
nents are of equal intensity but different
sign, we know that we have made a con-
sistent assumption and the state of stress
is possible and completely defined.
The state of stress is not completely
defined when the stress upon a single
plane is known, because there may be
any amount of simple tension or com-
pression along that plane added to the
state of stress without changing either
the intensity or obliquity of the stress on
that plane.
INTERNAL STRESS IN GRAPHICAL STATICS.
Principal Stresses. — In any state of
stress there is one pair of conjugate
stresses at right angles to each other, i.e.
there are two planes at right angles on
which the stresses are normal only.
Stresses so related are said to he princi-
pal stresses.
It has been previously shown that if
a plane be taken in any direction, and
the direction of the stress acting on it be
found, then these are the directions of a
pair of conjugate stresses of which either
may be taken as the plane of action and
the other as the direction of the stress
acting upon it.
Consider first the case in which the
state of stress is defined by a pair of
conjugate stresses of the same sign; i.e.,
the normal components of this pair of
conjugate stresses are both compressions
or both tensions.
It is seen that they are of opposite
obliquities, and if a plane which initially
coincides with one of these conjugate
planes of action be continuously revolved
until it finally coincides with the other,
the obliquity must pass through all in-
termediate values, one of which is 0°, and
when the obliquity is 0° the tangential
component of the stress vanishes. But
as has been previously shown there is
another plane at right angles to this
which has the same tangential compo-
nent; hence the stress is normal on this
plane also.
Consider next the case in which the
pair of conjugate stresses which define
the state of stress are of opposite sign,
i.e., the normal component on one plane
is a compression and that on the other
a tension.
In this case there is a plane in some
intermediate position on which the stress
is tangential only, for the normal com
ponent cannot change sign except at
zaro. It has been previously shown that
in case there is one plane on which the
stress is a shear only, there is another
plane also on which the stress is a shear
only, and that this second shear is of
equal intensity with the first but of
opposite sign. Let us consider then that
the state of stress, in the case we are
now treating, is defined by these oppo-
site shears instead of the conjugate
stresses at first considered.
Now let a plane which initially coin-
cides with one of the planes of equal
shear revolve continuously until it finally
coincides with the other. The obliquity
gradually changes from +90° to —90%
during the revolution, hence at some
intermediate point the obliquity is 0°;
and since the tangential component has
the same intensity on a plane at right
angles to this, that is another plane on
which the obliquity of the stress is also
0°.
We have now completely established
the proposition respecting the existence
of principal stresses which may be
restated thus:
Any possible state of stress can be
completely defined by a pair of normal
stresses on two planes at right angles to
each other.
As to the direction of these principal
planes and stresses, it is easily seen from
considerations of symmetry that in case
the state of stress can be defined by
equal and opposite shears on a pair of
planes, that the principal planes bisect
the angles between the planes of equal
shear, for there is no reason why they
should incline more to one than to the
other. We have before shown that the
planes of equal shear are planes of
separation between those whose stresses
have normal components of opposite
sign: hence it appears that the principal
stresses are of opposite sign in any state
of stress which can be defined by a pair
of equal and opposite shears on two
planes.
It will be hereafter shown how the
direction and magnitude of the principal
stresses are related to any pair of con-
jugate stresses.
For convenience of notation in discuss-
ing plane stress let us denote compression
by the sign +, and tension by the sign
Let us also call that state of stress
which is defined by equal principal
stresses of the same sign a fluid stress.
A material fluid can actually sustain
only a + fluid stress, but it is convenient
to include both compression and tension
under one head as fluid stress, the proper-
ties of which we shall soon discuss.
Let us call a state of stress which is
defined by unequal principal stresses of
the same sign an oblique stress. This
6
VAN NOSTRAND'S ENGINEERING MAGAZINE.
may be taken to include fluid stress as
the particular case in which the ine-
quality is infinitesimal. In this state of
stress there is no plane on which the
stress is a shear only, and the normal
component of the stress on any plane
whatever has the same sign as that of the
principal stresses.
Furthermore let us call that state
of stress which is defined by a pair
of shearing stresses of equal intensity
and different sign on two planes at
right angles to each other a right
shearing stress. We shall have occasion
immediately to discuss the properties of
this kind of stress, but we may advan-
tageously notice one of its properties in
this connection. It has been seen pre-
viously from considerations of symmetry
that the principal stresses and planes
which may be used to define this state
of stress, bisect the angles between the
planes of equal shear. Hence in right
shearing stress the principal stresses
make angles of 45° with the planes of
equal shear. We can advance one step
further by considering the symmetrical
position of the planes of equal shear with
respect to the principal stresses and
show that the principal stresses in a state
of right shearing stress are equal but of
opposite sign.
We wish to call particular attention
to fluid stress and to right shearing stress,
as with them our subsequent discussions
are to be chiefly concerned : they are the
special cases in which the principal
stresses are of equal intensities, in one
case of the same sign, in the other case
of different sign.
Let us call a state of stress which
is defined by a pair of equal shearing
stresses of opposite sign on planes
not at right angles an oblique shear-
ing stress. The principal stresses, which
in this case are of unequal intensity
and bisect the angles between the
planes of equal shear, are of opposite
sign. A right shearing stress may be
taken as the particular case of oblique
shearing in which the obliquity is in-
finitesimal.
We may denote a state of stress as +
or — according to the sign of its larger
principal stress.
Fluid Stress. — In Fig. 5 let xx and
yy be two planes at right angles, on
which the stress at o is normal, of equal
intensity and of the same sign; then the
stress on any plane, as x'x', traversing o
is normal, of the same intensity and
same sign as that on xx or yy.
For consider a prism a unit long and
of infinitesimal cross section having the
face mn \\ x'x\ then the forces fx and/^ 0
acting on the faces om and on are such
that
fx'fyi: om : on.
Now nm=\/om2 + on*, and the result-
ant force which the prism exerts against
nm is
/= v/.'+Z, S .: fx:f::om: mn.
But fx -±-om is the intensity of the
stress on xx and f-r-mn is the intensity
of the stress on x'x', and these are equal.
Also by similarity of triangles the result-
ant f is perpendicular to mn.
Fig. 6
V
/v
\ 1
A /
\X \
\/
\V[
y\
/o "\
X
\ ^\a;/
X
/
y \
\r
Eight Shearing Stress. — In Fig. 6,
let xx and yy be two planes at right
angles to each other, on which the stress
is normal, of equal intensity, but of
opposite sign; then the stress on any
plane, as ccV, traversing o is of the same
intensity as that on xx and yy, but its
obliquity is such that xx and yy respect-
ively, bisect the angles between the
direction rr of the resultant stress, and
the plane of action x'x' and its normal
y'y'-
INTERNAL STRESS IN GRAPHICAL STATICS.
For, if the intensity of the stress on
x'x' be computed in the same manner as
in Fig. 5, the intensity is found to be the
same as that On xx or yy, for the stresses
to be combined are at right angles and
are both of the same magnitude. The
only difference between this case and
that in Fig. 5 is this, that one of the
component stresses, that one normal to
yy say, has its sign the opposite of that
in Fig. 5. In Fig. 5 the stress on x'x'
was in the direction y'y', making a cer-
tain angle yoy' with yy. In Fig. 6 the
resultant stress on x'x' must then make
an equal negative angle with yy, so that
yor=yoy'. Hence the statement which
has been made respecting right shearing
stress is seen to be thus established.
Combination and Separation. — Any
states of stress which coexist at the same
point and have their principal stresses in
the same directions xx and yy combine
to form a single state of stress whose
principal stresses are the sums of the re-
spective principal stresses lying in the
same directions xx and yy : and con-
versely any state of stress can be separ-
ated into several coexistent stresses by
separating each of its two principal
stresses into the same number of
parts in any manner, and then grouping
these parts as pairs of principal stresses
in any manner whatever.
The truth of this statement is nec-
essarily involved in the fact that stresses
are forces distributed over areas, and that
as a state of stress is only the grouping
together of two necessarily related
stresses, they must then necessarily fol-
low the laws of the composition and
resolution of forces.
For the sake of brevity, we shall use
the following nomenclature of which the
meaning will appear without further ex-
planation.
The terras applied to
forces and stresses are :
Compound,
Composition,
Component,
Resolve,
Resolution,
Resultant.
The terms applied to
states of stress are :
Combine,
Combination,
Component state,
Separate,
Separation,
Resultant state.
Other states of stress can be combined
besides those whose principal stresses
coincide in direction, but the law of
combination is less simple than that of
the composition of forces; such combi-
nations will be treated subsequently.
Component Stresses. — Any possible
state of stress defined by principal
stresses whose intensities are px and
py on the planes xx and yy respect-
ively is equivalent to a combination
of the fluid stress whose intensity is
±i(Px + Py) on each of the planes xx
and yy respectively, and the right shear-
ing stress whose intensity is + -J ( px — py)
on xx and — i(px — py) on yy.
For as has been shown, the resultant
stress due to combining the fluid stress
with the right shearing stress is found
by compounding their principal stresses.
Now the stress on xx is
i(p* +p ) + h{r*-Pv)=p*
and that on yy is
i(P* +Py)-i(P* ~Py )=Py
and hence these systems of principal
stresses are mutually equivalent
In case py = 0, the stress is complete-
ly defined by the single principal stress
px , which is a simple normal compression
or tension on xx. Such a stress has been
called a simple stress.
A fluid stress and a right shearing
stress which have equal intensities com-
bine to form a simple stress.
It is seen that the definition of a
state of stress by its principal stresses,
is a definition of it as a combination of
two simple stresses which are perpendicu-
lar to each other.
There are many other ways in which
any state of stress can be separated into
component stresses, though the separa-
tion into a fluid stress and a right shear-
ing stress has thus far proved more use-
ful than any other, hence most of our
graphical treatment will depend upon it.
It may be noticed as an instance of a
different separation, that it was shown
that the tangential components of the
stresses on any pair of planes xx and yy
at right angles to each other are of equal
intensity but opposite sign. These
tangential components, then, together
form a right shearing stress whose prin-
8
VAN NOSTRAND'S ENGINEERING MAGAZINE.
cipal planes and stresses x'x' and y'y'
bisect the angles between xx and yy>
while the normal components together
define a state of stress whose principal
stresses are, in general, of unequal in-
tensity.
Hence any state of stress can be sepa-
rated into component stresses one of
which is a right shearing stress on any
two planes at right angles and a stress
having those planes for its principal
planes.
The fact of the existence of conjugate
stresses points to still another kind of
separation into component stresses.
THE MODULUS OF ELASTICITY IN SOME AMERICAN WOODS,
AS DETERMINED BY VIBRATION.
By Dr. MAGNUS C. IHLSENG.
Written for Van Nostrand's Magazine.
The importance of this factor, so
necessary for construction, is sufficiently
acknowledged to warrant the use or
arrangement of new methods for its
accurate determination. The various
direct methods which are now employed
are more or less elaborate, involving a
large outlay in apparatus. We have,
however, a more ready means for ascer-
taining this value, one which is not
usually resorted to, namely, by vibra-
tion.
When any rod or solid body is rubbed
by a resined woolen cloth in the
direction of its axis, it is urged into
longitudinal vibration and gives out a
note of high pitch. The particles of the
rod are excited by a force which acts
along the direction of the fibres and
they will move backward and forward,
thus executing an oscillation. This vi-
bratory movement of the particles pro-
duces a pulse running through the en-
tire length of the rod in a given time,
and this motion continues while the
exciting cause is acting, the velocity de-
pending upon the structure of the ma-
terial. The propagation of this vibra-
tion, however, depends upon the elastic
force of the molecules and not on the
tension which is applied externally. The
more elastic the body is the greater
will be the rapidity of transmission. So,
it is evident, that the rapidity of vibra-
tion, or, in other words, the pitch of the
note which the rod is sounding, depends
upon the velocity with which this pulse
is propagated. If, now, we ascertain
the pitch of the note, by counting the
number of vibrations per second, we
have determined the velocity of propa-
gation by substitution in this simple
formula :
v = 2 n.l,
in which v is the velocity per second,
and n the number of vibrations executed
by the rod, whose length is I. The
length may be two meters, the thickness
about 20 mm. The specimen should be,
of course, as free as possible from im-
perfections.
To measure the rate of vibration of
the rod, I employed a simple direct pro-
cess, which has been fully detailed, hav-
ing been read before the National Acad-
emy of Sciences, Oct., 1877.
In brief, the modus operandi is this;
the rod to be experimented upon is
clamped in the center by a vise, one end
being free, the other end having a small
brass pen fastened to it. This brass pen
is bent somewhat and rests upon a
smoked glass plate. When the rod is
set into vibration by rubbing it along
the free end, by a resined woolen cloth,
the glass plate is moved under the pen
by means of a falling weight. A tun-
ing fork of a known rate simultaneously
registers its vibration on the plate; the
two pens have now described two traces,
the number of vibrations in each depend-
ing on the ratio between the two notes
of the rod and fork. Two parallel lines
are drawn upon the plate, embracing a
given period of time. The number of
the waves in each of the two traees are
then counted between these parallel lines,
by means of a low power microscope.
MODULUS OF ELASTICITY IN AMERICAN WOODS.
9
In this manner, the rates of vibration
of several rods were determined. By
calculation, v was obtained, which by
substitution in the following formula,
gives us the the value for the coefficient
of elasticity ;
(39.37041 XvY
9
v=the velocity of sound in meters as cal-
culated above; g is the accelerating force
of gravity; m is the weight of one cubic
inch of the substance, in pounds; the
factor, 39.37041 is the number of inches
in a meter.
The following table shows the results
of the experiments upon the several
varieties of wood. The degree of
humidity of these specimens was not
found as they were well seasoned and in
the condition employed in commerce.
The determinations are all average
values of from ten to fifteen observa-
tions :
Cypress
Poplar
<<
<<
tt
Shell bark Hickorv
White Pine .".
White Pine
White Ash
White Ash
White Holly
Mahogany
Black Walnut
Wild Cherry
Yellow Pine
Red Oak
White Oak
Specific
Gravity.
.432
.482
.465
.417
.478
.476
.443
.425
.478
.922
.491
.432
.544
.541
.562
.540
.518
.693
.664
.650
.775
Length.
1.836 M
1.8384
1.83875
1.83672
1.650
83857
834
21236
114237
5505
8419
8426
8365
83826
3785
3491
37863
5601
0524
4947
4945
Number of
Vibrations.
1033.53
1107.97
1050.93
1132.8
1187 3
1339.98
1418.
2041.8
2035.47
1279.5
1227.21
1165.94
1159.13
1326.58
1532.6
1734.1
1413 26
2030.83
1395.04
1443.93
Velocity per
Second.
3797.2 M
4073.89
3864.79
4161.65
3918.14
4927.4
5201.2
4950.68
4650.4
4110.1
4713.4
4522.47
4282.44
4261.51
3657.4
4135.3
4780.7
4409.5
4274.5
4179.8
4316.5
Modulus of
Elasticity,
inch lbs.
901020
1157100
1004700
1044700
1061500
1710700
1733560
1506800
1496880
2253000
1577890
1278100
1443140
1421100
1087450
1335800
1712500
1949160
1754940
1644160
2090050
There have been few experiments upon
the elasticity of woods by any similar
methods of vibration. Wertheim,* who
alone has any extended investigations
upon this point, decides that the coeffi-
cient obtained by vibration is greater
than that from elongation, by abput a
per cent. This he explained by assum-
ing a slight increase of temperature as
produced by the compression of the
particles of the rod. More recent modi-
fications, however, show that the heat
disengaged in the transmission of this
motion has little influence.
The advantages of the present method
are evident, as the number of vibrations
are directly registered, a process, which
Weisbach, by the bye, considered im-
practicable.! I have also shown in my
* Annalen der Chemie et Physique, Ser. Ill, T. 12, p.
385, and Comptes i endus, Tome 23. p. 663.
+ Weisbach, Mechanics' of Engineering, Coxe, Vol. I,
p. 1077.
article, above alluded to, that this
method gives results which are lower
than those obtained from Kundt's air
method, by one per cent, or more; thus,
perhaps, bringing it nearer the truth.
Moreover, the rod registers the same
number of vibrations, within the limits
of error, that is given by a standard
tuning fork to which the rod has been
brought into unison.
The Don Pedro Segundo Railway
line has reached its highest point, an al-
titude of 3550 ft., 225 miles from Rio de
Janeiro, in traversing the gorge of Juan
Ayres, in the Mantiqueira range, whose
highest peak is Itatiaia, 8380 ft. in alti-
tude. The Pyrenees range, in Goyaz,
although not so towering in outline as
the Mantiqueira range, has been found to
be over 1000 ft. higher, and to be the high-
est in Brazil — its real backbone, in fact.
10
van nostkand's engineering magazine.
CIRCULAR CURVES FOR RAILWAYS.
By Pkof. WM. M. THORNTON, University of Virginia.
Written for Van Nostra:nd's Magazine.
§ 1. SIMPLE CURVES.
1. Setting out a circular curve:
The deflection angle of a circular curve
is the angle subtended at any point of it
by a chord one chain long. If this
angle d be given and the tangent at the
origin o, it is easy to set out such a
curve. Plant the transit at o, set the
vernier at zero, sight to t and clamp the
lower motion. Release the upper mo-
tion, deflect d to 01 and make 01 equal
to one chain. Deflect d again to 02 and
make 12 equal to one chain; and so on.
2. Elements of the curve:
3. Fundamental formulae:
It is obvious geometrically that DCT
D.- Whence the following formulae
sm.
D:
tan. T>—
The elements of such a curve are
d, the deflection angle,
r
s
t
D
radius,
semichord,
tangent,
total deflection.
Thus in the diagram CD = CD'=r,
DD' = 2s, DN=S, DT=D'T=:*, TDD'
=TD'D=D. All lengths are in chains
of 100 links, all angles in minutes.
sin. d-
1
2r>
the last formula is a special case of the
first. For when D=d, 25=1. These
formulae are exact and afford the solution
of all possible cases. In applying them
to numerical examples it is most con-
venient to throw them first into the
logarithmic form, thus:
Jjr=l. 69897— L sin. d,
Ls=Lr-f-L sin. D,
Lz=Lr + Ltan.D.
The following example shows the
most convenient order for conducting
the computation:
d=lS\ D = 24° 19'
23.55
1.69897
L sin. d
8.32702
Lr
1.37195
L sin. D
9.61466
L tan. D
9.65501
Ls
0.98661
U
1.02690
9.70
10.64
The computations are sufficiently sim-
ple. But as it would be necessary for
the engineer to carry into the field a set
of logarithmic tables and to interrupt
his work to perform the computations,
the approximate formulae in the follow-
ing article have been devised. These
CIRCULAR CURVES FOR RAILWAYS.
11
reduce the necessary computations to a
few easy divisions, by means of a small
collection of tables.
4. Approximate formulae :
If x be expressed in circular measure
sin. x=x-
x x
6 +120
sin. x <
Remembering then that dis expressed in
minutes and that sin. d=—. we have
2r
, 5400 n\r
d <
6.108002
The second member is less than -§- if
J<521; that is if r>3.30. No greater
curvature than this should be permitted
in railway curves. Accordingly the
formula
5400
nr
gives the value of d for a given r within
a half minute in defect. It is therefore
for railway practice as good as exact.
Hence if we put
5400
m = = 1118.81:
7t
S=m sin. D,
T=?n tan. D,
we have the formulae
dr=m, ds=S, dt=T*
5. Tables:
The tables required for use with this
method are a table for r with d as argu-
ment, and tables for S T, with D as
argument. Such tables arranged in a
convenient form are appended to this
article.
6. Short chords :
At the terminus of a curve it is fre-
quently necessary to use a short chord
to join it to the tangent. A short chord
is also frequently used to complete a
chain begun on the initial tangent. In
either case the appropriate deflection
angle is easily found. For if dx be the
required angle, cx the length of the
chord then
sin. dx = —
2r
But since dx is less than d we can put
7 dx
sm. dx=—
2m
.-. dx = dcx
7. Length of the curve:
The number of chords in the curve is
obviously given by the formula
nd=T>
The fractional part of n if any will by
the last article be the length of the short
chord necessary to complete the curve*
Thus in the example treated in (1, 3)
24°19/
n=— — T = 19.99:
to
so that the curve consists practically of
20 chains. If £=112', D=31° 12'
n=16.7l
so that the curve consists of 16 chains
and a short chord of 71 links, the deflec-
tion angle for which is
dx = 112/X0.71 = 80/
8. Long chords:
Chords running two or more stations
are often used to test the accuracy of the
field work. If x be the number of sta-
tions, cx the length of the chord
c~ = 2r sin. dx.
But
sin. dx:
m'
.-. dcx = 2Sdz-
Sdx is taken from the S— Table and cx
found by an easy division:
9. Ordinates:
Intermediate points on the curve are
fixed by means of ordinates or offsets
normal to the chord.
12
VAN NOSTRAND7S ENGINEERING MAGAZINE.
If AB be the chord, PAI the normal
to the chord, IQ the normal to the curve
we may disregard the difference between
PM, IQ and put PQ=y tne required
ordinate. If therefore PA=a?
y{2r-y)=x{l-x)\
or since y is very small in comparison
with r
y=
il-x)
2r
For the middle ordinate x=% and hence
1
2/o=
8r
For the quarter ordinates£=J and hence
y^f yo. In terms of the deflection
angle we have
2/0=0.00007274 d.
* For bending rails of length I the analo-
gous formula is
yo ==0.00007274 dl\
10 Cant:
The centrifugal force acting on a mass
m revolving in a circle of radius r feet,
with velocity v feet per second is — ;
the weight of the same mass is rag. The
resultant of these forces must be normal
to the road bed. Hence if G be the
gauge, H the cant or superelevation of
the outer rail both expressed in the same
unit
H_^2
G~ gr
In practice the velocity is usually
given in miles per hour V; and hence
3600 v = 5280 V,
<tfr=l7l887;
#=32.1695;
••• l=^°
where q is a constant factor such that
Lq= 7.58999
For the ordinary gauge 4' 8^" we
have for the cant in inches
H=0.00002198dV2.
* Reducing the coefficient to a continued fraction and
calculating the convergents we find for the middle ordi-
nate in links the practically exact and very simple formula
11 100* The side ordinates win be iT' Too' The formulse
are so simple that no tahle is needed.
or with a high degree of accuracy
H_22Va
d~ 106
The following table gives the values
of 1000 — for equidistant values of V.
15
20
25
30
35
40
45
50
5
9
14
20
27
35
45
55
11. Field Problems:
The problems which arise in the field
have been exhaustively treated by so
many writers that it will be necessary
simply to indicate the mode in which
our formulse and tables are applied.
The data are as follow:
A. The origin, the tangent there and
the terminus.
Measure DD'=2S, TDD'=D. Then
take S from the table. We shall then
have
s d
and the curve is set out as in (1, 1)
B. The origin, the terminus and the
curvature.
Measure DD' = 2S. Then S = ds;
whence D from the S table. Set out
DT)T=D and proced as in (1, 1)
C. The origin and both tangents.
1. Point of concourse of the tangents
accessible:
Plant the transit at T and measure the
exterior angle which is 2D ; measure also
the tangent TD=£. Then having got T
from the table we have
_ T D
d=Vn=~d
2. Point of concourse of the tangents
inaccesssible
Set out and measure PQ and the
CIRCULAR CURVES FOR RAILWAYS.
13
Measure the exterior angle T:
and take T from the table. Then
2D,
t—
~cV
D
angles P, Q. Or where this is impossible
determine the no by a traverse. Then
2D = P + Q,
PT=PQ4-n-^-, = PQ.|^
^ sin 2D' ^ S2D
Z=PT-PD.
D. The curvature and both tangents:
1. Point of concourse accessible:
The first formula fixes D, the origin.
2. Point of concourse inaccessible:
Set out and measure PQ and the
angles P, Q. Then
2D=F + Q,
PT=PQ.
sin. Q
=PQ,
'2D
t:
n=—.
sin. 2D
T
7r
D
d>
PD=PT-£.
The last formula fixes the origin.
12. Obstacles:
A. When the stations after x are no
longer visible from 0.
The telescope being set on x clamp
the vernier plate, remove the transit and
plant at x. Siujht back to o by the lower
motion and clamp. Reverse the tele-
scope and release the vernier plate.
Bring the vernier back to zero and con-
tinue setting out as from a new origin o' .
B. When two stations b, c are visible
from the origin o but the chord between
them bo cannot be measured.
To fixe
(1) Measure the long chord oc.
(2) Measure the chord from
second station back, ac.
the
(3) Range out bd--
1.
:aZ>, and make dc
13. Corrections:
Having run a curve from a given tan-
gent terminating in a certain tangent, it
is required to determine a curve which
will terminate in a parallel tangent.
(1) Without changing the origin.
Since the deflection remains the same
the new terminus Q will lie in the pro-
longation of DP where it cuts the
parallel tangent. Fix Q and measure
PQ. Then if s'=s + PQ
d'=-t
s
(2) Without changing the curvature:
Set out PP parallel to the initial tan-
gent, measure PQ and make DE=PQ.
14
VAN nostrand's engineering magazine.
Or measure the horizontal distance QR 14. To find the curvature of a eiven
—h, between the tangents and make curve:
Make,,AB=BC=ED=l ch. and AE
perpendicular to AC. Then
tf=CAD=i CBD,
J_ 1
r~CD~"2BE
§ 2. COMPOUND CURVES.
_ 1. When the tangents are on opposite
sides of the chord which joins the termi-
nal points of a railway curve and are
equally inclined to it, a simple curve
CIRCULAR CURVES FOR RAILWAYS.
15
consisting of a single circular arc may be
used to unite them. But when the
angles of inclination are unequal a com-
pound curve, consisting of two circular
arcs with their curvatures, in the same
direction and tangent to each other at
their point of juncture must be used to
write them.
2. Formulae:
Let A,A' denote the angles of inclination
of the tangents to the chord.
2w denote the exterior angle be-
tween them.
n,n' denote the length of the nor-
mals.
D,D' denote the deflections of the
arcs.
r,r' denote the radii.
d,d; denote the deflection angles.
2c denote the lengths of the chord.
Then it is obvious that
(1) 2a> = A + A' = 2D + 2D',
2{r—n){r,—n') cos. 2cof
which is reducible to the form
(2) r sin. A-fV sin. A'= — cos.2w-f-c
or (2')
7YI C
Jsin. A'-f-c^'sin. A=— cos.2w + — dd\
c m
or (2")
7 m - \
d=— sin. A
c
COS. to
sin. A
sin. A'
A'H:
co and
Then measure HAT=D and
A. One radius assumed:
1. Set out A'H so that HA'T'
2Sw
: d'
set out A'J to meet AJ in J making
HA'J=D. Then set out the curves
A J, A'J by the rules of § 1.
2. Having assumed r computed by
equation (2") above and set out the two
branches of the curve as in § 1.
B. One deflection assumed.
1. Having assumed D we have D'=w
— D. Set out AJ, A'J to meet in J,
making TAJ=D, T'A'J'=D' and then
set out the curves AJ, A'J by the rules
of § 1.
2. Having assumed D and found D'
we compute the other elements of the
arcs by the following formulae
sin. co
sin.(A'-D'),
sin. co
sin. (A-D),
dz
d'.
D
d'
It would be easy to show by means of
equation (2) that the best conditions of
curvature are obtained by making the
common normal JCC perpendicular to
the common chord AA'. That is, by
making 2D = A, 2D' = A'. It is alto-
gether possible, however, that the con-
struction of the curve thus obtained may
be attended with disadvantages whicn
more than compensate its benefits.
16
VAN NOSTRAND'S ENGINEERING MAGAZINE.
§ 3. REVERSE CURVES.
1. When the tangents are on the same
side of the chord which joins the termini
neither a simple curve nor a compound
curve can be used. We must have re-
course to a curve composed of two cir-
cular arcs tangent to each other at their
junction with their curvatures in oppo-
site directions.
2. Formulae:
Let A,A' denote the angles of inclination
of the tangents to the chord.
2w denote the interior angle be-
tween them.
n,n' denote the lengths of the nor-
mals.
D,D' denote the deflections of the
arcs.
r,r' denote the radii,
d,df denote the deflection angles.
2c denote the length of the chord.
Then it is obvious that
(1) 2w:=A-A/ = 2D-2D',
(r + r'y=(n-ry+(n' + r'y
— 2(?i— r)(n' + r') cos. 2«
which is reducible to the form
(2) r sin. A + r' sin. A'=c—
rr
or (2')
r sin. a)
7 m . . c sin. A
d=— sin. A. ;
c _ r'
1 sin. A'
c
3. Solutions:
CIRCULAR CURVES FOR RAILWAYS.
17
A. One radius assumed:
1. Set out AH so that HAT=w, AH
= ~ and measure HAT' = D'. Then
d
set out AJ to meet A'H in J so that
HAJ=D'. Then the curves A J, A' J
may he set out by the rules of § 1.
2. Having assumed rf compute d by
equation 2') above, and then set out the
two branches of the curve as in § 1.
B. One deflection assumed:
1. Having assumed D we have D'=D
— id. Set out A J, A' J to meet in J, so
that TAJ=D, T'A'J^D' and then set
out the curves AJ, A'J by the rules of
§ l-
2. Having assumed D and found D'
compute the other elements of the arcs
by the following formulas:
sin. o)
sin. (A' + D')}
sin. (D+A).
d=
d' =
-?;
S'
s"
d''
4. Special case:
When the tangents are parallel u) — o\
whence J lies in A A' and D = D'=A.
The relation between the radii becomes
/>
sin. A
Unless some specific reason forbids it
is best to make r=r'; hence
c
, D
d
remembering that D=A
§ 4. SWITCHES AND FROGS.
1. The data in setting a frog are the
length and travel of the switch and the
number of the frog. The circular meas-
ure of the switch angle is the quotient
of the travel by the length. The circu-
lar measure of Ihe frog angle is the
reciprocal of its trade number.
2. Setting the frog:
In the diagram H is the heel of the
switch, T the toe, F the point of the
Vol. XIX.— No. 1—2
frog, TN" the travel, c the center of the
main line, o the center of the turn out.
OTC is therefore the switch angle, OFC
the frog angle.
Let G denote the gauge.
J denote the travel.
denote the circular measure of the
switch angle,
denote the circular measure of the
frog angle,
denote the radius of the main line,
denote the radius of the outer rail
of the turn out.
d denote the deflection angle of the
main line.
6 denote the deflection angle of the
outer rail of the turn out.
If afi be two sides of a triangle in-
cluding the very small angle x and c the
third side, then very nearly
c*=(a-by + abx\
Apply this formula to the triangles
TOC, FOC. We have for OO2 the equiv-
alent expressions
(CT-OT)2 + OT.CT.pa
= (CF-OF)2 + OF.CF.?2,
... (CT-CF)(CT + CF-20T)
= OT(CF.q*-CT.p*).
Now GF=r-iG, CT=r + ^G-J, OT
=p; hence
(G-J)(2r-J-2i»)
=p[(r-iG)?-{r+iG-J)p']
18
VAN NOSTRAND'S ENGINEERING MAGAZINE.
But in comparison with r, G and J
may be neglected; the equation becomes
2(G-J)(r-P)=rp(q*-p>)y
" d a~ 2(G- J) '
When the curvatures are in opposite
directions we have simply to change the
sign of d. When the main line is
straight d=o. In any case it is simply
necessary to deduce 6, set out TF and
make the point of concourse F.
3. Tables:
In the ordinary case J — 5", G=4' 8'^;
whence
6— d=v(q*.— £>2),
W=20025,7l.
The following tables give the values
of vq*f vp2 for various frog numbers and
switch lengths:
No. of frog. . . .
4
1251.6
5
801.0
6
556.3
7
8
9
10
11
12
vo2
408.7
312.9
247.2
200.3
165.5
139.1
Switch Length.
8
12
16
20
22
24
26
28
30
W)2
54.3
24.1
13.6
8.7
7.2
6.0
5.1
4.4
3.9
This table enables us to solve imme-
diately any example that can occur.
(1) Given the original deflection angle
123', the switch length 26 feet, the frog
number 9, then 6 — d—2^.2 — 5.1 = 242';
d=365'.
(2) Given the original deflection angle
94', the switch length 30 feet, the frcg
number 6, then for a turn out on the
convex side S + d— 556.3 — 3.9=552.4,
tf=458'J.
Such are the " tedious and complicated
calculations " which Trautwine dreads.
[P.B. 404].
4. If the main line is straight the
exact formulas are very simple. Their
employment is however attended with
no advantage.
H
If in the figure the frog distance
TF=/, then since o=q—p, TFN=£
{',+p) ,=.JL-£„
sin. Uq-p)
f
2 sin. i (q-p)
5. Frog distance:
The first of these formulas gives the
approximate result
2(G-J)
/ ' p + q
When G=4' b"|, J = 5" this gives for /
in feet
103
f-U(pTq)
It would not be difficult to show that
this formula is approximate in defect,
the proportion of error being about
24
which in the most unfavorable case does
not amount to more than 0,13 of one per
cent. Accordingly it will be found that
the values of / given in the following
table are more precise than Trautwine's
[P.B. 402] obtained it is presumed from
an exact formula but by a more circuit-
ous process :
(See Table on following page.)
§ 5. SYLLABUS OF FORMULAE.
1. Exact formulas:
Lr= 1.69897— L sin. d,
Ls=I> + L sin. D,
Ltf=Lr + L tan. D.
CIRCULAR CURVES FOR RAILWAYS.
19
1
4
5
6
7
8
9
10
11
12
8
284
340
392
440
485
526
564
600
634
12
301
366
426
483
537
589
637
683
727
16
311
380
445
508
568
626
681
751
785
20
317
389
458
524
589
651
710
768
824
22
319
392
462
530
566
660
722
781
839
24
321
395
466
536
603
668
731
793
852
26
323
397
470
540
609
675
740
803
864
28
324
399
473
544
614
682
747
811
874
30
325
401
475
548
618
687
754
819
883
This table gives the values of f to the
nearest tenth of a foot
2. Approximate formulae:
dr=?n, ds=S, dt=T, d/i=D.
3. Deflection angle of a short chord:
dx = dcz
4. Long chord:
2Sda;
a
5. Middle ordinate in links:
_8 d_
y°~ 11*100
6. Cant in inches; common gauge:
22f?Va
:20025.71.
H
106
7. Compound curves:
D+D'=1(A+A')=a>,
dsin. A' + d' sin. A=— cos.2w -f - dd\
c m
rf cos.2«>
j m . c'sin.A
d—— sin. A. 7
l--sin.A'
c
8. Reverse curves:
D-D'=|(A-A')=",
d sin. A' + d' sin. A=-dd'-~ sin.2a>,
m c
r' sin.2w
7 m . . c 'sin. A
d— — sin. A.
c r' . A ,
1 sin. A'
c
1 9. Deflection angle of turnout from a
curve:
°~2(G-J) +a
For common gauge and travel 5 inches
7)1
§ 6. EXAMPLES.
This section contains solved examples
to illustrate the rules and processes of
the method which has been explained.
1. Simple curve: — data, D=]8° 37^
d=2° 50'
1117 97
re=-m=Vo=6-57
The curve therefore consists of six
complete chords and a short cord of 57
links whose deflection angle is 97°. The
radius 10.11 is taken from the table
And
y0=r-X 1.7=1.2
Finally from the S— table
37
S=531.2 + — X 28.4=548.7
bO
548.7
This or any other long chord may be
used to test the precision of the field
work.
2. Simple curve:— data, 5=10.32; d=V
47'
S = 107X10.32 = 1104.2
.'. D = 39°58'
20
VAN NOSTRAND' S ENGINEERING MAGAZINE.
44
22-— =22.41
107
r=16.37— -X7.4=16.07
5
y=TiX 1.07 = 0.8
3. Simple curve: — data, s= 8.42; D = ll
29'
29
S = 328.0 + — X29.4.
60
342.2
34^ 2
d= =40.63 say 40|
8.42
.-. 2s'=2 X
342.2
40|
16.83
689
40f
16.94
8
2/o"nxo'40§=0,3
It will be observed that the corrected
chord 2s' falls 1 link short of the old
chord. This variation is entirely admissi-
ble and unavoidable with a transit that
reads, as is usual, only to 20 seconds.
4. Simple curve: — data £=19.25, 2D
= 48° 24'
12
T=765.3 + — X 36.2 = 772.5
60
19.25
1452 12
=36—:
40 40
36.30
y0=nxo.4=o.3
S = 699.1 +|X27.3 = 704.6
R— Table, Argument d,
n 704.6
2s= = 35.23.
20
5. Compound curve: — data 2c=8.43;
21°11/
A=14° 23'; A
Assume A=2D; then
D = 7° ll'i D' = 10° 35'£
, 525X215.2
'4.215X316.0
:85
d'=
525X316.0
4.215X215.2
183
„=i!= = 5.09 „'=i= = 6..5.
85 183
6. Reverse curve: — data 2c = 11.28;
= 16° 24'; A/=10° 42'
Assume
D = 15°; D' = l° 27';
fe4,0y.X^°=lU.5;
5,64X277,3
d'.
402.7X42.0
5.64X43.5
69
900
7.:
1
69
= — = 1.23
114.5
7. Tarn out: — c?=130'; no. of frog, 8;
length of switch, 24.
vq*=312.9
^2=6.0
306.9
d=130.0
tf=437
The corresponding radii are 13.22 and
3.94. From a drawing made to scale
the frog distance may be found approxi-
mately. It is best however to determine
the place of the frog by setting out the
turnout.
0°
1°
2?
3°
4°
5°
6°
7°
8°
9°
0'
00
2865
1432
955
716
573
478
409
358
318
0'
5'
34377
2644
1375
929
702
564
471
404
354
315
5'
10'
17189
2456
1322
905
688
553
465
400
351
313
10'
15'
11459
2292
1273
981
674
546
458
395
347
310
15'
20'
8594
2144
1228
859
661
537
452
391
344
307
20'
25'
6875
2022
1186
838
649
529
446
386
340
304
25'
30'
5730
1910
1146
819
637
521
441
382
337
302
30'
35'
4911
1809
1109
799
625
513
435
378
334
299
35'
40'
4297
1719
1174
781
614
506
430
374
331
296
40'
45'
3820
1637
1042
764
603
498
424
370
327
294
45'
50'
3438
1563
1011
747
593
491
419
366
324
291
50'
55'
3125
1495
982
731
583
484
414
362
321
289
55'
0°
1°
2°
3°
4°
5°
6°
7°
8°
9°
21
S— Table, Argument D.
0
1
2
3
0
0.0
30.0
60.0
90.0 \
1
298.5
328.0
357.4
386.7 j
2
587.9
616.0
643.9
671.5 !
3
859.4
885.3
910.9
936.2 i
4
1104.9
1127.7
1150.1
1172.2 !
5
1316.7
1335.8
1354.5
1372.7
6
1488.6
1503.4
1517.6
1531.5 |
7
1615.2
1625.2
1634.7
1644.0
S
1692.7
1697.7
1702.1
1706.1 :
119.9
415.8
699.1
961.2
1194.0
1390.6
1544.9
1652.3
1709.4
6
149.8
444.9
726.4
985.9
1215.4
1408.0
1557.8
1660.8
1712.3
179.7
473.8
753.5
1010.3
1236.4
1425.0
1570.3
1667.8
1714.7
209
502
780
1034
1257,
1441,
1582,
1674
1716.5
8
9
239.2
268.9
531.2
559.6
807.0
833.3
1058.2
1081.7
1277.4
1297.2
1457.7
1473.4
1593.7
1604.7
1681.3
1687.3
1717.8
1718.6
T— Table, Argument D.
0
1
2
3
4
0
0.0
30.0
60.0
90.1
120.2
1
303.1
334.1
365.4
396.8
418.8
2
625.6
659.8
694.5
729.6
765.3
3
992.4
1032.8
1074.1
1116.2
1159.4
4
1442.3
1494.2
1547.7
1602.9
1659.9 !
5
2048.5
2122.6
2200.0
2281.0
2365.8
6
2977.1
3100.9
3232.7
3373.4
3524.2
7
4722.5
4992.0
5290.1
5622.1
5994.3
8
9748.1
10853.
12230.
13999.
16354.
150.4
460.6
801.5
1203.6
1718.9
2454.8
3686.1
6414.9
19647.
6
7
180.7
211.0
492.9
525.5
838.3
875.8
1248.8
1295 2 ,
1779.9
1843.2;
2548.3
2646.8s
3860.6
4049.5 j
6894.0
7445.3
34581 .
32797. !
i
s
241.6
585.5
913.9
1342.9
1909.0
2750.7
4254.3
8086.7
49222.
9
272.2
591.9
952.8
1391.9
1977.3
2860.7
4477.7
8842.8
78221 .
0
1
2
3
4
5
6
7
81
ON THE CAUSE OF THE BLISTERS ON "BLISTER STEEL.
By JOHN PERCY, M.D., F.R.S.
Journal of the Iron and Steel Institute.
In the process of making steel, which
is so largely practiced at Sheffield, bars
of iron, usually of Swedish or Russian
manufacture are embedded in charcoal
powder, and kept heated to bright red-
ness during about a week or ten days,
according to the degree of carburization
desired. Carbon is thereby imparted to
the iron, and steel is the product. The
bars operated upon are generally about
3 inches broad and £ of an inch thick.
How the carbon finds its way even to
the center of such bars is a question not
yet satisfactorily solved, though it pos-
sesses high scientific interest, and has
been much discussed. It is not however
my intention to consider that question
on the present occasion; but to commu-
nicate to the Institute experimental evi-
dence as to the cause of the singular
phenomenon which accompanies this
process of converting iron into steel,
namely, the occurrence of blister-like
protuberances on the surfaces of the
| bars. This appearance is so characteris-
| tic and so constant, that the name of
i "blister-steel" is applied to such bars.
I The protuberances are hollow, exactly
; like blisters, and vary much both in
number and size: some are not larger
! than peas, while others may exceed an
j inch in diameter, and they are always
confined to the surfaces of the bars, for
I have a specimen of " blister steel " in
my collection, in which there is a single
blister as large as a small hen's egg, pro-
truding equally from each of the flat
opposite surfaces of the bar.
With regard to the cause of these
blisters there has been a difference of
opinion. I will take the liberty of mak-
ing the following quotation on the sub-
ject from my volume on "Iron and
Steel," published in 1864:— "They (i.e.
22
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the blisters) appear to be due to inter-
nal local irregularities and gaseous ex-
pansion from within, while the iron was
in a soft state from exposure to a high
temperature. There is no doubt that
all forged bars, for reasons previously
assigned [and which I stated in consider-
able detail], contain more or less inter-
posed basic silicate of iron irregularly
diffused throughout. Now, what should
be the effect of the contact of carbon, at
a high temperature, with particles of
this silicate ? Most probably the re-
duction of part of the protoxide of iron
with the evolution of carbonic oxide,
and if this be so, then it seems to me,
the formation of blisters may be satis-
factorily accounted for. Admitting this
explanation to be correct, a bar, which
has been ;made from molten malleable
iron, should not blister during cementa-
tion [the term used to designate the pro-
cess in question of making steel]; and,
should this prove to be the case, it»
would not be difficult to prepare such a
bar with particles of cinder [ferrous sili-
cate] imbedded, and by subsequently ex-
posing it in a converting furnace, ascer-
tain positively whether blisters would
occur only in places corresponding to the
cinder."
It has, I think, been conclusively
proved that all bar iron manufactured
by charcoal finery processes, or by pud-
dling, must contain, intermixed, some of
the slag, which results from the conver-
sion of pig iron into malleable iron by
such processes, in which, let it be re-
membered, the malleable iron is never
actually melted. In the quotation which
I have given I mentioned only ferrous
silicate as constituting the slag; but I
ought, also, to have included free oxide
of iron, doubtless magnetic oxide. The
bars converted at Sheffield are chiefly
Swedish, and are generally manufactured
by the so-called Lancashire process.
On a visit to the great steel works of
Messrs. Firth, at Sheffield in February
last, Mr. Charles H. Firth was so good
as to undertake, at my suggestion, to
settle the question whether blistering
would occur in the converting process in
the case of a bar of iron which had been
actually melted, and so freed from all
intermixture of ferrous silicate, or mag-
netic oxide of iron. The experiment
was accordingly made, and with good
effect, of confirming, and, I think I
might almost say, establishing the cor-
rectness of the explanation which I ven-
tured to submit concerning the cause of
the formation of the blisters. On the
9th of last May, Mr. Firth informed me
that be had melted Swedish bar iron,
and cast it into a flat ingot, which he
had carburized in the converting furnace
in the usual manner; and, at the same
time, he forwarded to me a piece broken
from the ingot, after conversion: this
piece was about six inches long, three
inches broad, and a little more than half
an inch (exactly T7¥) thick; it showed a
fracture at each end characteristic of
converted steel, but there was not the
slightest indication of a blister.
The other experiment, which 1 sug-
gested, seems scarcely to be needed,
namely, that of cementing a cast bar of
malleable iron, in which bits of slag, or
magnetic oxide of iron, had been imbed-
ded. But should any one be willing to
make such an experiment, probably the
best way would be to cast an ingot of
Swedish iron, drill a hole or two in it to
the depth of about the center, insert a
bit of slag in one hole, and a bit of mag-
netic oxide of iron in another, then plug
up the holes hermetically by a screw or
otherwise, and convert in ordinary way.
THE STRUCTURAL PROVISION FOR THE DISCHARGES
THE RAINFALL OF LONDON.
OF
From " The Builder.'
The serious damage and discomfort
inflicted on so large an area of London
by the rain of the night and morning
of the 10th and 11th of April afforded a
subject of very serious contemplation to
all who are engaged in building, or in
dealing with that first duty of the archi-
tect, the art of keeping houses dry. It
is satisfactory to find that the first ac-
count which was published of the burst-
PROVISION FOR THE RAINFALL OF LONDON.
23
ing of a main sewer in the Brixton-road
has been subsequently contradicted, and
that it was not to the failure of any por-
tion of the Main Drainage works, in as
far as their structural strength was con-
cerned (that is to say, as a question of
strength apart from the question of
capacity), that so serious a misfortune is
to be attributed. At the same time, it
can hardly be argued that the inhabit-
ants of a city like London ought to be
exposed to those floods and watery dis-
asters which have of late been but too
common in the southern portion of the
metropolis. Convulsions of nature, in-
deed, may be beyond the forecast of hu-
man wisdom to prevent or to render
harmless. Thebursting of a water-spout,
or the violent down-pour occasioned by a
throw on a low-lying district a mass of
tornado, may water that will for a time
choke up the best engineering arrange-
ments for outfall. The rain of the night
of the 10th of April, however, was by
no means of so altogether exceptional a
kind as is called a meteoric phenomenon.
It was heavy, continuous and prolonged,
rather than sudden and violent. Its fall
was stated at two inches in London streets
(and as much as three inches at Green-
wich) in about nineteen hours, a quantity
which, while giving a quantity of 200
metric tons per acre, is not so great that
it should overtax our means of dis-
charge. Double the former depth of
rainfall was gauged in some parts of
England in the wet time some two years
ago. At all events, it is an amount of
rain for which experience tells us that
we ought to provide, and the possible
occurrence of which was distinctly re-
ferred to by the engineer of the Main
Drainage works as having been re-
garded as possible. It would be a de-
plorable outcome of the engineering
science of the nineteenth century for us
to be told that when two inches of rain
falls within twenty-four hours, or when
an east wind comes at the back of a high
spring tide, the inhabitants of a large
part of London are to resign themselves
to partial submergence, with all the
damage to property, as well as to health,
involved in such a calamity. But unless
the recent disaster be taken up by the
public and by the press with rather
more persistence, as well as with rather
better information than was the case
with . regard to the last floods, little
practical good will be derived from so
costly a lesson.
The subject is so immediately con-
nected with the primary structural and
sanitary question of the proper method
of securing an outfall for storm-water,
that it may be instructive to glance at
the physical features of London, imme-
diately to the south of the Thames, and
at the change in the course of the out-
i flow of rainfall that has been effected by
j the Main Drainage works. The river
! Thames, from the confluence of the
I Wan die at Wandsworth to that of the
j liavensbourne at Deptford, makes an
irregular triple curve, or series of three
loops, to the north, running at an ex-
treme distance of as much as 2| miles
from the chord of this compound arc.
There are reasons for supposing that the
ancient bed of the river took a more
direct line than thai of the present
channel. At all events, the whole area
which we have described lies below, —
some of it as much as sixteen feet below,
— the contour line of ten feet above
Trinity high -water mark of the year
1800, — a level which high tides now not
unfrequently surmount. The ground
was marsh, so recently as the Restora-
tion; and is represented as such in an
engraving of the entrance of King
Charles II. into London, which exists in
Mr. Gardner's remarkable collection of
drawings, engravings, and other publica-
tions illustrative of the history and
architecture of the metropolis. Gradu-
ally, as the progress of population
covered this marshy site with building,
the house-drainage became a source of
more and more disquietude. The low-
lying area above indicated covers as
much as twenty square miles. It is in
places as much as five feet or six feet
below high- water mark. The sewers
which, since the year 1815, were gradu-
ally constructed so as to run mostly in
an easterly direction, into the Thames,
had but little fall, and, except at the
period of low tide, were tide-locked and
stagnant. After long-continued rain
they became overcharged, and were
unable to empty themselves during the
short period of low water. Many days,
therefore, often elapsed during which
the rain accumulated, and the sewage
was forced into the basements and eel-
24
VAN nostrand's engineering magazine.
lars, to the destruction of much valuable
property, and to the great loss of health
among the residents.
There is no doubt that a considerable
benefit has been conferred on this dis-
trict by the works of the main metro-
politan drainage, even though these
works have proved inadequate to the
discharge of a steady rain like that of
April 10th, 1878. It was the design of
the works to arrest the torrent water
before it descended into this low-lying
district. For this purpose two lines of
sewer were constructed, one approxi-
mately parallel to the course of the
river, and the other approaching the
line of the first at an acute angle. The
first, or main line, commences at Clap-
ham, — the second, or branch, at Dulwich.
Between them they drain an area of
about twenty square miles, including
Tooting, Streatham, Clapham, Brixton,
Dulwich, Camberwell, Peckham, Nor-
wood, Sydenham, and part of Greenwich.
It was stated in the original report as
to these main sewers that they were of
sufficient capacity to carry off all the
flood-waters, so that they would be
entirely intercepted from the low-lying
districts, which were thus to be protected
from floods. The falls of the main line
are fifty-three feet, twenty-six feet, and
nine feet per mile to the Effra sewer at
the Brixton-road, and thence to the out-
let 2^ feet per mile. The old course of
the Effra fell into the Thames near
Yauxhall Bridge. The diversion of this
torrential channel so as to flow into the
Thames at Deptford is in accordance
with the principles of outfall drainage
laid down and followed out by the
Rennies, and by the most able and dis-
tinguished engineers. But the combina-
tion of a torrential diversion with a
main sewerage drainage is another mat-
ter. As a question of quantity alone, it
is now manifest that the sectional area,
varying from a barrel of seven feet in
diameter to a section of ten feet six
inches by ten feet six inches with a cir-
cular crown and segmental sides and
invert, is not adequate to the discharge
of a quantity of rain which is not more
than half of that which has been known
to occur in some parts of the country, in
twenty-four hours, within the last two
years. The sectional area of a seven
foot barrel is, say, forty square feet.
We may take that of the larger section
as about eighty square feet. A fall of
two inches of water, in twelve hours,
over an area of twenty square miles,
gives a flow of 2,085 cubic feet, or 13,000
gallons, per second, which would require
a velocity of about sixteen miles per
hour in order to be discharged through
a culvert of the larger of the two sec-
tions named, — a velocity which is practi-
cally impossible. This calculation must
be confronted with the fact that in pro-
posing to turn the storm water of Lon-
don into the main sewerage, the engi-
neer considered that a rainfall of J inch
per day, in excess of the maximum flow
of the sewers, was all that had to be
provided for. Sir J. Bazalgette, in his
report on the Main Drainage system in
March, 1865, stated with perfect truth
that "there are, in almost every year,
exceptional cases of heavy and violent
rain storms, and these have measured
one inch, and sometimes even two inches,
in an hour." The maximum flow of sew-
age is estimated, in the report cited, at
a volume equal to that produced by a
rainfall of 80.01 inch per hour, or, as
above mentioned, 0.25 inch in twenty-
four hours. As a rule, then, the area of
the sewers has been doubled, in order to
provide for an arbitrarily restricted
quantity of rain, amounting to less than
an eighth-part of that which was known
occasionally to occur.
" But," the report continues, " excep-
tional rain storms must be provided for,
however rare this occurrence, or they
would deluge the property on which
they fell."
This brings us to the point of which
the due appreciation is rendered so
urgent by the disaster of the 10th of
April. The question of the provision for
storm-water, or excessive rainfall, is one
of the most serious that can demand the
attention of the architect or of the engi-
neer, especially in the case of a large
city. In those parts of the world where
rain of from one inch to two inches or
even more per hour, is not uncommon,
the architect is compelled by necessity
to look facts in the face, and to provide
for the safe discharge of what would
otherwise prove destructive floods. Thus
in the south of Europe the streets, of the
principal cities are so constructed that
they offer ready and efficient channels
PROVISION FOR THE RAINFALL OF LONDON.
25
for the torrents that spring up in formi-
dable volumes after an hour or two of
rain. In Turin, in Naples, and in other
cities, the arrangements for this purpose
are very effective. It is true that they
are not complicated by being mixed up
with the scavenger drainage of the
cities. But that is the very point at
issue. The question is, ought the rain-
fall to be turned into the sewers ?
In cases where no regular artificial
water supply is provided for a large
collection of dwellings, but where the
sewage of the houses is carried off by
underground culverts, the utilization of
the rain water, at least in part, for the
flushing of the sewers is indispensable.
That much may be freely admitted as
necessary in the interests of sanitation.
But one of the main objects in the sup-
ply of a volume of water varying from
twenty-five to forty gallons per head of
the population per diem is to provide a
regular and adequate amount of water
carriage for the removal of the sewage.
The most that can be said in favor of
the admission of storm water into the
sewers, as far as the sanitary service of
the population is concerned, is that it
will not materially affect the regularity
of the daily discharge. With such a
supply of water as we have named, there
is no need for flushing at irregular and
uncontrollable intervals. The two sys-
tems are not only different, but incon-
sistent. When rain is depended on for
flushing, an arrangement is proper that
differs materially from that which is
suited to the discharge of a regular daily
quantity of diluted sewage. When the
latter is properly provided for, — when
the inflow of the water runs through a
well-devised system of pipes, and the
outflow of the same water, bearing with
it the refuse products of city life, is
carried on through a proper series of
pipes and culverts, any capricious excess
of quantity, such as that arising from
storms, only complicates matters. If,
on the one hand, the sewers be provided
so large as to deal with, not only the
ordinary but the extraordinary rainfall,
their dimensions must be so large as to
cause an enormous expense. The figures
above given will show that something
like sixteen times the sectional area that
is required for the daily regular service
must be added to that section in order
to give anything approaching certitude
as to dealing with storm water; although
the occasions on which that section
would be filled will be very rare.
We are not about to pronounce an ex
cathedra opinion on a subject as to which
different views are entertained by pro-
fessional men of experience; nor do we
wish to offer any criticism as to details
of the existing arrangements. It is
rather our object to elicit general princi-
ples as to the truth of which debate is
unnecessary; and to point out the prac-
tical result of the application of these
principles. Such, wTe conceive, is the
useful and important function of the
scientific press; and such the line which
should divide the remarks of a public
writer from the report of a consulting
engineer.
It is certain that, in providing for the
drainage of a town or city, one of three
courses must be taken. Either the rain-
fall and storm- water must be excluded
from the sewers, or it must be accommo-
dated by them, or there must be a more
or less perfect combination of the two
systems; that is to say, part of the rain
will be, and part will not be, carried off
by the sewers.
Of these three methods, the second,
which is the simplest, is supposed to be
excluded from consideration on account
of its expense. In the case of London,
for example, instead of being designed
of a capacity, as at present, to carry off
twice the maximum flow of sewage, the
sewers, in order to be efficient under any
stress of weather, must be of a size to
carry off at least seventeen times that
volume. Even this considerable addi-
tional cost, however, is not the main
difficulty. Sixteen times the discharging
area of channel would not imply sixteen
times the cost of construction, although
it would no doubt involve 2^- times as
much outlay, or even more. But the
real difficulty, in the case of London, lies
in the fact that the entire extra volume
has to be pumped up for a height of 36
feet in order to enter the Thames. There
is indeed, an outfall for storm water
provided at Deptford, but there is, even
at that point, a lift of 18 feet from the
low-level sewer. If we take the smaller
lift alone we still find that either the
capacity of the pumping apparatus must
be so arranged as to enable it to deal
26
VAN NOSTRAND S ENGINEERING MAGAZINE.
with a sixteen or seventeen fold quantity
of water, on a sudden emergency, or that
the enlarged sectional area given to the
sewers would be of no value as a protec-
tion to the district. Practically, there
fore, the provision for the whole of the
storm water by the sewers is pretty well
out of the question.
If we take the opposite view, namely,
that the storm water should be excluded
from the closed system of water supply
and of sewage we commence with the
advantage of a diminution of cost, and
better sewers as respects sewage alone.
Both as regards the pumping appara-
tus, half the actual provision would on
that system have been adequate.
The question, however, would then
have arisen. How to deal with the rain ?
But this very question is no less import-
ant, and, we must be allowed to say, is
not brought much nearer to a satisfac-
tory solution, under the adoption of the
the present plan, which is one of a mixed
character, accommodating a part of the
rainfall in the ordinary sewers, and pro-
viding (or rather as it seems not provid-
ing) for the remainder by supplementary
works.
It is well to observe that the suffering
caused by the flood of the 11th of April
is by no means confined to the district
drained by the Metropolitan Board of
Works. The area of the rainfall was
limited. Although it rained during the
night over large part, and probably over
the whole, of the watershed basin of the
Thames it was on approaching London
that the traveler became aware of any-
thing like a phenomenal rainfall. More
rain fell on the north than on the south
of London. The river Wey was not un-
usually, full at the time when the rivers
Colne and Brent were bringing down
exceptionally high floods. The Medway
also was greatly swollen. Thus, if we
take the case of Brixton as one most fit
to be examined, it is not to be thought
that the diversion of the Effra is a sole
cause of difficulty; although it may
afford an unusually forcible illustration
of the operation of the mixed system of
outfall at present in vogue.
The principle of the existing works
for the drainage of London is thus stated
by Sir J. Bazalgette. " As it would
not have been wise, or practicable, to
have increased the size of the intercept-
ing sewers much beyond their present
dimensions, in order to carry off rare and
excessive thunderstorms, overflow weirs,
to act as safety valves in times of storm
have been constructed at the junctions
of the intercepting sewers with the main
valley lines. On such occasions the sur-
plus water will be largely diluted, and
after the intercepting sewers are filled,
will flow over the weirs, and through
their original channels into the Thames."
How far this plan has been adhered to
in the case of the Effra line of drainage
we shall, perhaps, learn trom the report
which Sir J. Bazalgette has been direct-
ed to prepare. But the report of 1 v 65,
from which we are quoting, says further,
"The old Effra sewer, which fell into
the river near Vauxhall Bridge, has been
diverted, through this (the intercepting)
sewer to a new outlet at Deptford, and
the old line has been filled in and aban-
doned." There seems to be some con-
tradiction between these two passages of
the report; and we are thus unable at
the moment to ascertain how far the
principle of allowing an overflow to
take the course of the original outfall
has been carried out in the case of the
Brixton sewers.
Whatever be the arrangement in this
particular instance, it is evident that the
safety-valves provided have been entire-
ly inadequate to carry off an amount of
rain that may at any time descend on
London. This, however, is, in our opin-
ion, by no means the most important
part of the question. It is one thing to
have drainage that works very well on
ordinary occasions, but that breaks down
in a storm, and another matter to have
a system that adds to the mischief of a
storm that of a widespread pollution by
sewage. The expression "the surplus
waters will be largely diluted " contains
the marrow of that to which we object
on sanitary as well as on economical
grounds. If a system of sewers is so
constructed as to be capable of convey-
ing only a fraction of an unusual rain
fall, it ought to be the care of the engi-
neer that no excess over that fraction
should be allowed to enter the sewers.
By entering in detail the contributory
drains, sweeping them of their contents,
filling the intercepting lines, and then
overflowing not only through streets but
through houses, the rain takes the most
PROVISION FOR THE RAINFALL OF LONDON.
27
mischievous and disastrous course into
which it can possibly be»turned.
We confess that this consideration has
very great weight in inclining us to the
opinion that, all things considered, econ-
omy, as well as public health, would be
consulted by the systematic exclusion
of the rainfall from the sewers. It is
certain that if the whole of the rain be
turned into this channel of discharge,
and if the latter proves at times totally
inadequate to carry it off, — the worst
kind of evil remains. The limitation of
the ingress of the rain is a more difficult
matter than its total exclusion.
The question then would arise, it may
be urged, how to provide for the rain-
fall? But this is the very question
which is involved under the mixed sys-
tem. The mixed system provides, let
us say, for 364 days out of the year, but
breaks down under a deluge on the 365th.
Somehow or other we are bound to pro-
vide for that exceptional 365th day.
The question is, can we not most surely,
most thoroughly, and most economically
provide for the entire disharge of the rain
whether normal or abnormal without
turning it into the sewers ?
We prefer to put this question as a
suggestion. We take it for granted that
London has the right to claim an effec-
tual protection from floods, whether
arising from the Thames, or poured
down from the surrounding water-shed.
At the present moment there can be no
doubt that the expenditure of nearly
eleven million sterling in drainage and
embankment works has placed large
districts of London in a far worse posi-
tion, when exceptional floods occur, than
they were in fifty years ago. It is stat-
ed in the report by Mr. Redman, to
which we have before referred, that the
height of the Thames floods has been
increased by the Embankment on the
north of the river. It is clear from the
reports of the late disaster that the
action of the southern drainage works
has been such as to pollute the torrent
water that overflowed streets and houses
with sewage. These are results of a
mixed system, which, to our minds, has a
fatal flaw. It is that of being a fine
weather system alone. Would it not be
better to look foul weather in the face ?
Would not a system that should provide
specially for rainfall, whether it be 0.01
inch per hour or 0.25 inch per hour, fully
and simply, without choking the sewers,
or overpowering the pumping engines as
soon as the lower dimension was much
exceeded, be the most economical, as
well as in all other respects the best.
For the discharge of rain, not by the
sewers two modes are possible, — which
of course, may be combined according
to circumstances. One is the original
method, which is capable of very admir-
able management, of making the road-
way form channels, or a channel, for the
rain. The other is that of constructing
special subways, for culverts, for that
purpose. The city of Turin is subject
to violent rain. Storm clouds collect
over the Alps, and after two or three
days of intense heat often burst in a sud-
den deluge on the city. The violence of
the rain is far greater than any to which
we are accustomed in this country.
But the architects and surveyors of
Turin have made such provisions that
the rain comes as a friend, not as a de-
stroyer. The streets are carefully paved
for the most part with broad lines of
dressed stone for the wheels to run over
and intermediate pitching for the horses,
edged with raised footpaths, and pierced
with gully-holes at certain appropriate
points. It is by no means unusual to
see from 2 inches to 3 inches of water
running over one of the main streets of
Turin after half an hour's rain. But all
that follows is, that for so many min-
utes a clear bright stream of that depth
runs along the road. By the time that
the storm has ceased, and pedestrians
and carriages can venture forth from the
shelter to which they were driven, the
rain has run off as rapidly as it at first
rose, and a clean street is all that remains
to tell of the downfall.
In Naples more formidable torrents
find their way through the city in storms,
owing to the greater amount of catch-
water area which intervenes between
the city and the crest of the Apennines.
The sirocco, a southern wind, brings a
tropical fall of rain, not only over the
city, but over the country for miles
round. To protect the city there is a
large intercepting fosse, or moat which
is practicable as a road in dry weather
but which becomes a veritable river in
storms. Besides this, the streets are ar-
ranged in accordance with the lie of the
28
VAN nostrand's engineering magazine.
land, so as to carry off the water. In
some places pavement, as in Turin, lead-
ing to culverts at proper places, pre-
vents any permanent inconvenience from
the results of a tropical downpour. But
in others and notably in the road leading
into Naples from Caserta, a wide street
dips gradually towards the center, in
which is a paved open channel, dry, ex-
cept in time of rain, and readily carrying
off any moderate quantity of water. But
when a sirocco deluge comes on, a vast
body of water seeks this channel. The
inclination of the sides of the streets is
such as to allow the gradual widening
as well as deepening of the torrent, in
proportion to the exigencies of the mo-
ment. In the utmost volume of the rain
the sides of the street remain above the
flood, and light iron bridges, under
which it is easy to drive in fine weather,
afford means of crossing to pedestrians
when the central part of an important
thoroughfare is converted from road into
river.
The conditions of the Italian cities are
far more severe, as regards liability to
floods, than any that prevail in England.
For that reason Italian architects have
have been obliged to look flood in the
face, and to provide for its ready dis-
charge. For that reason no one in
Naples or in Turin suffers any inconve-
nience from violent storms, beyond the
risk of a wetting if he ventures out in
them; for an umbrella is but a child's
toy if opposed to an Alpine storm or to
a sirocco shower. That similar arrange-
ments might be introduced into the
streets of London cannot be questioned
by men of foreign experience. That by
a thorough consideration of the worst
possible case, the means of providing for
the discharge of an inch of water in an
hour, London might be rendered perfect-
ly safe against a rain flood, will not be
doubted by any who gives attention to
the subject. That a due consideration
of what is needful in extreme emergency
would lead to a provision that would
at all times be efficient, and that would
take a great load off the whole system
of sewerage and of pumping, is the thesis
that we submit for consideration. As
we must provide for the worst — under
penalty of extraordinary loss — is it not
better to do so in the first instance and
at the same time to arrange for the dis-
charge of all our rain water, whether it
be an inch, or a hundredth of an inch, in
an hour, without inflicting on the works
of the sewerage a duty that may at any
moment rise to the double of the neces-
sity amount of work, and which, as soon
as it exceeds that double, commences the
work of disaster ?
THE PURIFICATION OF WATER.
By GUSTAV BISCHOF, F.C.S.
From "Journal of the Society of Arts."
The subject which I have the honor
to bring under your notice to-night is of
a somewhat embarrassing magnitude,
though it is my intention to confine my-
self solely to the purification of water
for sanitary purposes. It would be easy
to lay before you a number of facts and
conclusions bearing on the means by
which this may be more or less effected,
but it would be almost like building a
house without foundations were I not
first to attempt an understanding be-
tween us, or, at least, to explain my
views as to the nature of the work which
a purifier of water has to perform.
Absolutely pure water, containing ex-
clusively oxygen and hydrogen in the
proportion in which they chemically
combine to form water, is not known,
even in our laboratories. The foreign
matter in ordinary water is either gase-
ous, mineral, or organic.
The gases which generally occur in
water, namely, free oxygen, nitrogen and
carbonic anhydride, ' are, in moderate
quantities, not only harmless but even
desirable. Oxygen and carbonic an-
hydride render water sparkling and
palatable. It is chiefly to them the so-
called mineral waters owe their palata-
THE PURIFICATION OF WATER.
29
bility, and they appear to have a bene- 1
ficial effect upon the digestive organs. |
Other gases, such as sulphuretted hydro- !
gen, indicate organic impurities and are
objectionable.
Whether hard or soft water be more
conducive to health has not been defi-
nitely settled, but probably a moderately
hard water is more wholesome than
either excessively hard or soft water.
Of greater consequence are the impuri-
ties of organic origin, consisting of
living or dead animal or vegetable mat-
ter. These occur in water partially as
solid particles in a state of suspension
and partially in solution. Suspended
impurities may be separated to a certain
extent by mechanical filtration through
sand, paper, or other materials. How-
ever, even in the brightest water, solid
bodies are frequently discovered under
the microscope, or by passing an electric
ray through the water, as I will by-and-
bye illustrate experimentally. These
microscopic solid bodies are extremely
minute in their largest sizes, the smaller
objects remaining probably unseen, even
by the aid of our most powerful micro-
scopes. They are, therefore, not unfre-
quently considered amongst the matter
which is in a state of solution. If these
bodies are of an organized nature, we
have in all probability to search amongst
them for the virus which produces a
number of the most disastrous diseases.
This naturally leads me to the germ
theory. Whether and how far germs
are at the root of disease, or whether the
latter are due to common chemical
agencies, is a much contested question.
And yet it is a matter of considerable
importance, upon which the decision
hinges, whether we may depend upon
the laws of chemistry in deciding any
question relating to water supply, or
whether this belongs more or less promi-
nently to the physiologist. Being my-
self a believer in the germ theory, I
wish to lay before you a i'ew arguments,
however incomplete they necessarily
must be. We designate as contagia
such parasitic infectious agencies as are
transferable from one individual into the
healthy body of another; there, we sup-
pose, they multiply, when finding a
favorable nidus, and produce a specific
disease, similar to the one from which
they originate, such as cholera or typhoid.
What evidence, then, tends to demon-
strate the organized nature of these con-
tagia? They have never been with cer-
tainty isolated, no one has ever seen
them, and yet, if we find that they are
endowed with properties peculiar to
living bodies, we can hardly evade the
conclusion, that they themselves belong
to a class of organisms. I think we shall
agree that the property of producing
their like by separation of part of their
j body and of growing by assimilation of
I extraneous matter, is peculiar to organized
beings. Let us, then, see whether con-
tagia exhibit any evidence of such prop-
erties. Chauveau has proved experi-
mentally that the virus of small-pox,
sheep-pox, and glanders is independent
of quantity. The minutest particle, such
as can only be obtained by great dilution,
produces the disease with apparently the
same virulence as concentrated matter.
j The remarkable epidemic of typhoid at
i Lausanne (Switzerland) in 1872, is, on
the other hand, a practical demonstra-
| tion, amongst many others, that the
| virus of typhoid produces fearful results
I in a state of dilution, in which the dead-
liest of the known chemical poisons
would, as a matter of certainty, have
had no effect whatever. Is it not proba-
ble in the highest degree, that we have
to account for that apparent independ-
ence from quantity by a power of repro-
duction and rapid self-multiplication ?
Again, the direct connection between
cholera, or typhoid, and preceding cases
of the same disease, has in so many in-
stances been traced as to justify in my
opinion the conclusion that nobody has
ever been attacked by either of them,
unless the specific virus had been trans-
ferred to him originally from a person
afflicted with the same disease. It is, of
course, out of my power to substantiate
this to-night, by detailing a great many
instances, but I may suppose that most,
if not all, of you are familiar wTith them.
Such unvariable connection can scarcely
be explained, except by assuming that
the virus possesses the peculiarity of
organized beings of self-reproduction, in
other words, as Dr. Simon expresses it
in one of his reports to the Privy Coun-
cil, that contagia multiply, in case after
case, their respective types, with a suc-
cessivity as definite and identical as that
of the highest order of animal or vegeta-
30
VAN NOSTRAND S ENGINEERING MAGAZINE.
ble life. Indeed, unless we assume this,
we cannot understand the constant re-
lation to a parent case and the total ab-
sence of any de novo generation by
chance or coincidence.
There are, further, numerous instances
of epidemics which appear to prove al-
most to demonstration that the virus of
typhoid is peculiarly virulent, when gain-
ing access to our milk supply. Similarly
we have reason to believe, that the virus
is more active, when passed into water
largely contaminated with organic mat-
ter, than when passed into comparatively
pure water. This is at once explained,
if we assume that the virus is capable of
assimilating organic matter, in fact, of
living upon it.
In cases of poisoning by known chemi-
cal agencies on the other hand, say, by
lead, the poison is not transferable from
person to person; and whenever certain
conditions are given, such as water of a
certain composition passing through lead
pipes, any person may, on drinking that
water, be poisoned without any reference
to a previous case. Small, but traceable,
quantities of lead have frequently been
found in the blood, liver, and other
human organs, without any distinct in-
jury to the system. Minute quantities
of lead have sometimes been taken
habitually for years, until the poison
gradually accumulated to an extent suffi-
cient to cause serious disorders, or even
death. In his standard work on Hy-
giene, the late Dr. Parkes says with ref-
erence to this : — " On the whole it seems
probable, that any quantity over l-20th
of a grain (of lead) per gallon should be
considered dangerous." Such poisons
therefore are not independent of quan-
tity; on the contrary, let me also remind
you, some of the strongest chemical
poisons, such as strychnine, arsenic, lead,
copper, and morphia, are given in small
quantities as remedies against various
ailments. Thus there appears to exist a
sharp and remarkable contrast between
ordinary chemical poison and the virus
of cholera, typhoid, and similar diseases.
Dead organic matter forms a large
proportion of ordinary filth, and all kind
of filth is more or less liable to contami-
nate our water supplies. Those diseases,
which are produced by common septic
ferment, or by the ordinary putrefactive
changes which dead organic matter un-
dergoes, are therefore of peculiar interest
to us.
As far back as about the middle of
last century, Albrecht von Haller de-
monstrated that putrescent organic mat-
ter in aqueous solution may be fatal, if
injected into the veins of animals. The
symptoms lie observed are, inflammation
of the digestive organs, and disturbance
of the nervous system. The animal
heat is sometimes considerably in-
creased, sometimes decreased. Panum
succeeded in extracting a poison from
putrid matter, which he describes as so-
luble in water, insoluble in alcohol, and
free from albuminous matter. It is not
destroyed at a boiling heat, and acts ap-
parently like ordinary chemical poisons,
the virulence being proportionate to the
quantity injected. Arnold Hiller, on the
other hand, has recently extracted an al-
buminous body from putrid meat by
means of glycerine, which is precipitated
and destroyed at a boiling heat, and so-
luble in alcohol and acids. On being
injected under the skin of a rabbit, the
extract, in which Hiller failed to discover
any organisms, showed no effect for
several days. Then, apparently after
the ordinary period of incubation, the
symptoms of blood poisoning made their
appearance until the rabbit died. The
poison was reproduced in the body of
the animal, and by transferring it from
rabbit to rabbit, Hiller calculated that in
the tenth generation 1- 120th of a drop
of the original glycerine extract was
sufficient to kill a rabbit in fifty-two
hours. The symptoms were, fever,
asthma, increased solution of the red
blood corpuscles and diarrhoea. If Hil-
ler's observation was conclusive as to the
absence of organisms in the original ex-
tract, common chemical poison would
appear capable of producing effects
which I have endeavored to show can
only be attributed to living organisms.
But I venture to suggest, that the ab-
sence of the lowest forms of organic
life, or their germs, can, at the present
time at least, be hardly proved con-
clusively, excepting by the absence of
their ordinary visible effects, for there is
certainly evidence of life beyond the
power of our microscopes, and we can-
not know what we might see if their
magnifying power were increased ten or
a hundred fold. The disastrous conse-
THE PURIFICATION OF WATER.
31
quences which must be expected from
the drinking of water, which is polluted
by fermenting organic matter are, at any
rate, illustrated by Hiller's experiments.
Upon what condition, then, does the
wholesomeness, of a water supply de-
pend ? I cannot answer this by simply
classifying the different sources of sup-
ply in one way or another, and laying
down a rule that such and such sources
are objectionable, or require purification,
because those sources, which generally
furnish an excellent supply, are some-
times contaminated and vice versa. But
water must always be looked upon with
the more suspicion the greater its lia-
bility to contamination by sewage, and
more especially by human discharges, as
these may carry with them the most
dangerous specific seeds of disease. Thus,
shallow well and river water are gen-
erally most largely polluted, whilst at
the same time they are very extensively
used for water supply. If we find these
two attributes, namely, extensive use
and pollution combined, it is worth our
attention to inquire somewhat more
closely into the alleged danger arising
from the use of rivers and shallow wells
as sources of water supply.
Rivers are generally largely fed by
polluted surface water from cultivated
land, and by vast volumes of sewage
and other polluting waste materials. In
the Registrar General's returns we read
from time to time that a variety of most
disgusting matter may be traced in
Thames water, not only at the intakes of
the*several water companies in London,
but even after filtration through sand,
although the water is then mostly free
from disagreeable smell or taste. From
this we see that we cannot rely upon the
outward appearance, the brightness,
palatability, or absence of color and
smell, in forming an opinion of the
wholesomeness of a water.
The danger arising from the drinking
of river water, especially in times of
epidemics, is well illustrated by the ex-
perience of Glasgow. The mortality
there, per 10,000 of population, during
the three cholera epidemics of 1832,
1847, and 1854, was respectively, 140,
106, and 119, or, on the average, 122.
During this period the water supply was
derived exclusively, or almost exclusive-
ly, from the Clyde. Then followed the
epidemic of 1866, after, in the meantime,
the Loch Katrine water had been intro-
duced. What was the result? The
mortality from cholera decreased from
the average of 122 to only 1.6, or to less
than one and a half per cent, of that
figure. There is no showing that this
can be attributed to any other cause
than the abandonment of the Clyde as a
source of water supply.
Do not believe that this is an excep-
tional case. A glance at the map ap-
pended to the Sixth Report of the Rivers
Pollution Commission will show the in-
finitely small area, which, excepting the
Scotch Highlands, is covered by unpol-
luted river basins.
I have not been able to lay hold of
any experimental proof in favor of the
hypothesis of self-purification, of at least
our English rivers, by oxydation; but in
the Sixth Report of the Rivers Pollution
Commission we find rather the reverse.
The dilution, to which sewage is being
subjected in rivers, may be a safeguard,
to some extent, against common filth;
but if contagia be organized bodies or
individuals, dilution offers, in all proba-
bility, no protection against propagation
of disease by their agency. This, I
think, must be followed from the experi-
ence gathered during the epidemic at
Lausanne, to which I have already re-
ferred, and from other instances. It fol-
lows also, from a consideration of the
extraordinary power of multiplication
which, at any rate, some of the lowest
forms of organic life exhibit. Thus, F.
Cohn, a great authority on these matters,
has calculated that one single bacterium
might, within less than five days, fill up
by its progeny the whole ocean, supposing
they found a sufficiency of food.
The remarks about river water apply
also more or less to shallow well water.
A striking illustration of the dangerous
character of this source of water supply
was furnished by the epidemic of typhoid
in Broad Street, London.
It is impossible, within the time at my
disposal, to enter into any more particu-
lars as to the different sources of water
supply, but I wish to offer a few general
observations on this point.
It is not sufficient that a water supply
should be generally of a more or less
satisfactory quality, nor that its average
state should not give rise to any serious
32
VAN NOSTRAND'S ENGINEERING MAGAZINE.
apprehensions. Otherwise, we would
find ourselves unprepared and unpro-
tected when the worst condition arrives,
or when owing to the prevalence of epi-
demics, more than ordinary precaution
should be required. In illustration of
this, I believe that at ordinary times
there is no actual danger in drinking,
almost throughout the year, the water
supplied from the Thames to the greater
part of London, if it is sufficiently filtered
through sand. This must be accepted in
the face of the comparatively low mor-
tality we have. But now and then,
especially in times of floods, the water
deteriorates, sometimes very seriously,
and we even read of excremental matter
being then traced in it under the micro-
scope. This is certainly quite serious
enough; but I ask you, is there any
guarantee whatever that, should London
be visited by an epidemic, our experience
would be any better than that of Glas-
gow during the Clyde water period ? It
would, therefore, certainly be a great
boon could we here have a water supply
as pure as that from Loch Katrine; but,
as long as this appears impracticable, we
ought at least to have some additional
means beyond those at present employed
of purifying Thames water during cer-
tain periods of the year, and during epi-
demics.
By-and-bye I will return to this point,
but in the meantime let me direct your
attention to some of the most prominent
materials employed in the purification of
water. Some have either exclusively or
prominently a mechanical action, sepa-
rating like a fine sieve the coarser parti-
cles of suspended matter; others act
chemically upon the foreign mineral or
organic matter, and reduce the latter
more or less to harmless constituents.
The organic matter retained by me-
chanical purifiers must gradually under-
go decomposition, and the water, in pass-
ing through them, takes up more or less
of the decomposing matter. It is thus
intelligible that such a water may,
physiologically speaking, be impurer,
and may be less wholesome after, than
before, filtration, should even chemical
analysis indicate an improvement. To
this class of materials belong mainly
sand and wood charcoal, though the lat-
ter for a very short time has also a slight
chemical action. The more frequently
the materials are changed, and the more
they are aerated during filtration, the
more perfect will be their purifying
action.
With the exception of animal char-
coal and spongy iron, I have not been
able to lay hold of any conclusive evi-
dence of the efficiency of the materials
proposed as chemical purifiers. They
both have been extensively used in
domestic filters.
The success of any material used for
domestic filtration largely depends upon
the arrangement of the filters in which
they are used. These should be as easily
manageable, and as simple in construc-
tion, as is compatible with efficient work-
ing. In insisting upon the former, let us
not overlook the latter portion of this
sentence. The remark that absolutely
pure water is not known, even in our
laboratories, sufficiently explains that
the purification of water is not a simple
or easy operation, the efficient perform-
ance of which must be expected to give
some little trouble. The easiest and
simplest way is, after all, not to filter
water at all, and it is but reasonable to
expect that its purification should be
in some ratio to the care we bestow upon
it. We should, therefore, not be satisfied
to leave the filter entirely to the care of
servants, or even frequently without
giving them any guidance how they are
to manage it.
In all domestic filters easy access
should be given to the user himself for
cleaning and recharging, as it is indis-
pensable that chemical purifiers should
be renewed from time to time, and, as a
rule, the more frequently they are re-
newed the better. Instead of the re-
newal, a cleansing of the material is
sometimes recommended, by passing the
water through the filter in the opposite
direction to that ordinarily employed.
By these means a passage may be opened
for water through the filtering medium,
however its pores had been clogged with
filth, but the latter will never be removed
efficiently. If any one doubt this, let
me remind him of* the difficulty which
we find in keeping even the smooth sur-
face of our slate cisterns in a clean con-
dition. The slimy deposit adheres most
tenaciously, and must adhere still more
tenaciously to a granular, mare or less
porous, material. How often a material
THE PURIFICATION OF WATER.
33
requires thus to be renewed depends,
largely, upon the energy of its chemical
action upon organic matter.
If these considerations are conclusive,
I must condemn all filters in which the
materials are enclosed between slabs,
which are cemented into the filter case;
as this, by not giving access to the con-
tents, encourages the undue prolongation
of their use. From, the same point of
view, all materials are objectionable
which, being in the form of porous slabs
or balls, are not accessible throughout
their mass. And, just in passing, let me
warn you against the use of sponges,
which, although excellent and convenient
mechanical strainers, are truly a hotbed
for the lower forms of organic life.
The water is passed through the ma-
terials mostly downwards, sometimes up-
wards, or laterally. There are, of course,
advantages and disadvantages incidental
to each of these methods, but I believe
that, by downward filtration, under
otherwise like conditions, the most per-
fect purification is effected. The water,
in passing through a granular material,
upwards or laterally, has a tendency to
force a passage through certain channels,
wherever it finds the least resistance,
without being uniformly disseminated
through the material. Another defect
of upward filtration is that the deposit
of any filth, which mostly collects where
the water enters the material, is ex-
cluded from view, and even largely
from our sense of smell, instead of being
exposed and giving us warning. Down-
ward filtration, whilst free from these
disadvantages, renders filtering materials
liable to choke, owing to their natural
tendency to follow the course of the
water.
A filter ought to yield as much water,
in a given time, as can be efficiently puri-
fied by the material, necessitating some
arrangements for accurately regulating
the flow of water. This arrangement
ought, preferably, to be independent
from any compression of the filtering
medium, as, by simple compression, a
satisfactory regulation cannot practi-
cally be obtained, and should it even be
obtained in the first instance, as the yield
necessarily decreases at once as soon as
any suspended matter is deposited from
the water between the pores of the ma-
terial.
Vol. XIX.— No. 1—3
The construction of domestic filters
would, nevertheless, be comparatively
easy, could one always depend upon a
little common sense in their use. But it
is necessary to guard, as far as possible,
against ignorance and mischief, even at
the risk of complication. A point fre-
quently disregarded by the user is that
portable filters should oe paced in a cool
locality, free from any vitiated air, and
the filter taps ought to be situated as
conveniently as possible, so as to en-
courage the use of filtered in preference
to unfiltered water. If the unfiltered
water supplying the filter be stored in
cisterns, they should be kept clean, and
have no connection with water-closets or
drains.
These are the main points which have
guided me in designing the different
forms of spongy iron filters. The ordin-
ary portable domestic filter consists of
an inner, or spongy iron, vessel, resting
in an outer case. The latter holds the
"prepared sand," the regulator arrange-
ment and the receptacle for filtered
water. The unfiltered water is, in this
form of filter, mostly supplied from a
bottle, which is inverted into the uppei
part of the inner vessel. After passing
through the body of spongy iron, th^
water ascends through an overflow pipe.
The object of this is to keep the spongy
iron, when once wet, constantly under
water, as otherwise, if alternately ex-
posed to air and water, it is too rapidly
oxidized.
On leaving the inner vessel the water
contains a minute trace of iron in solu-
tion, as carbonate or ferrous hydrate,
which is separated by the prepared sand
underneath. This consists generally of
three layers, namely, commencing from
the top, of pyrolusite, sand, and gravel.
The former oxidizes the protocompounds
of iron, rendering them insoluble, when
they are mechanically retained by the
sand underneath. Pyrolusite also has
an oxidizing action upon ammonia, con-
verting it more or less into nitric acid.
The regulator arrangement is under-
neath the perforated bottom, on which
the prepared sand rests. It consists of a
tin tube, open at the inner and closed by
serew caps at the outer end. The tube
is cemented water-tight into the outer
case, and a solid partition under the per-
forated bottom referred to. It is provided
34
van nostrand's engineering magazine.
with a perforation in its side, which forms
the only communication between the up-
per part of the filter and the receptacle for
filtered water. The flow of water is
thus controlled by the size of such per-
foration. Should the perforation be-
come choked, a wire brush may be in-
troduced, after removing the screw cap
and the tube cleaned. Thus, although
the user has no access to the perforation
allowing of his tampering with it, he has
free access for cleaning. Another ad-
vantage of the regulator arrangement, is
that, when first starting a filter, the ma-
terials may be rapidly washed without
soiling the receptacle for filtered water.
This is done by unscrewing the screw
cap, when the water passes out through
the outer opening of the tube, and not
through the lateral perforation.
Various modifications had, of course,
to be introduced into the construction of
spongy iron filters, to suit a variety of
requirements. Thus, when filters are
supplied by a ball-cock from a constant
supply, or from a cistern of sufficient
capacity, the inner vessel is dispensed
with, as the ball-cock secures the spongy
iron remaining covered with water.
This renders filters simpler and cheaper;
and I incidentally remark that on this
principle the larger sizes of filters, be-
yond portable domestic filters, are fre-
quently constructed.
As the action of spongy iron is de-
pendent upon its remaining covered with
water, whilst the materials which are
employed in perhaps all other filters
lose their purifying action very soon,
unless they are run dry from time to
time, so as to expose them to the air, the
former is peculiarly suited for cistern
filters.
Cistern filters are frequently con-
structed with a top screwed on to the
filter case by means of a flange and
bolts, a U-shaped pipe passing down
from this top to near the bottom of the
cistern. This tube sometimes supplies
the unfiltered water, or in some filters
carries off the filtered water, when up-
ward filtration is employed. This plan
is defective, because it practically gives
no access to the materials; and unless
the top is jointed perfectly tight, the un-
filtered water, with upward filtration,
may be sucked in through the joint,
without passing at all through the ma-
terials. This I remedied by loosely sur-
rounding the filter case with a cylindri-
cal mantle of zinc, which is closed at its
top and open at the bottom. Supposing
the filter case to be covered with water,
and the mantle placed over the case, an
air valve is then opened in the top of the
mantle, when the air escapes, being re-
placed by water. After screwing the
valve on again, the filter is supplied with
water by the syphon action taking place
between the mantle and filter case and
the column of filtered water, which
passes down from the bottom of the
filter to the lower parts of the building.
These filters are supplied with a regu-
lator arrangement on the same principle
as ordinary domestic filters. The wash-
ing of materials, on starting a filter, is
easily accomplished by reversing two
stop-cncks, one leading to the regulator,
the other to a waste-pipe.
Another form of filter has been
specially adapted for the use on board
ships, the splashing of water, or shifting
of the materials, consequent to the roll-
ing of the ship, being prevented by
suitable arrangements.
For the requirements in India and
other colonies, a filter had to be con-
structed combining lightness, easy and
safe packing, easy management and
cheapness. In this there is no inner ves-
sel, the spongy iron being kept covered
with water by the joint action of two
tin tubes, one sliding loosely over the
other. The outer tube reaches from the
top of the filter to a well with perforated
sides, which rests on a watertight parti-
tion on the top of the receptacle for fil-
tered water. The inner tube is closed at
its base, reaching from the top of the
spongy iron to some distance below the
partition, through the center of which it
passes. Within the receptacle for filtered
water this tube is provided with a regu-
lator similar to the one in the ordinary
domestic filter. Thus the water is made
to pass through the filtering materials,
which rest on the water-tight partition,
and the well enters the latter, ascends
between the two tubes, and descends
through the inner tube, whence it passes
through the regulator opening to the re-
ceptacle for filtered water. A perforated
lid on the top of the materials is ar-
ranged to be tied down during transport,
to prevent shifting of the contents.
THE PURIFICATION OF WATER,
35
Permit me now to explain briefly what
spongy iron is, and to make a few sug-
gestions as to its probable action as a
purifier of water.
Spongy iron is metallic iron, which has
been reduced from some oxide of iron
without melting the product. I have
tried various arrangements for the pro-
duction of spongy iron, including the
Siemens' revolving steel furnace, and
believe that a reverberatory furnace of
suitable construction is best adapted to
the purpose. The weight of spongy iron
is about 1 cwt. per cubic foot, or one
quarter of that of ordinary iron which
has been fused. Its more powerful puri-
fying action, as compared with ordinary
melted iron, is largely based on the fine
state of division. But if we bear in
mind certain properties of spongy
platinum, we can easily understand that
the difference is not solely due to the
physical condition of the spongy ma-
terial, which may have affinities differing
from those of ordinary iron. This is at
once indicated by its property of decom-
posing water without the presence of an
acid. Spongy iron also reduces nitrates
and the carbonaceous and nitrogenous
organic matter. Whilst it thus appears
to have essentially a reducing action,
there are also indications of an oxidizing
process. Thus it appears that, under
certain conditions, perhaps under the in-
fluence of some oxide, resulting from the
gradual oxidation of the metallic iron,
the ammonia may disappear entirely,
being probably converted into nitric
acid.
I need not explain to the members of
the Chemical Section, that spongy iron
is most energetic in precipitating any
lead or copper, but even to chemists it is
a remarkable fact, that it should reduce
the temporary hardness of water very
considerably, and the permanent hard-
ness slightly. I cannot offer any ex-
planation of the latter reaction, but the
former, the reduction of the temporal
hardness, is probably due to the affinity
of the first product of oxidation, or fer-
rous hydrate, for the carbon anhydride,
which is the solvent of the calcic carbon-
ate. Ferrous carbonate is formed, and
the calcic carbonate precipitated. From
some reports, we shall presently see that
this action was found to continue equally
energetic for upwards of a year.
I have frequently been asked the
question, what becomes of the organic
impurities when filtering water through
spongy iron. The reactions are of a
complicated nature, and, up to the
present moment, I can hardly give more
than a few hints about them. .
In two successive papers, one read be-
fore the Royal Society last year, the
other recently, I have referred to a gas
which I observed within the bulk of
spongy iron, after it had been in use for
some time. It is sometimes explosive,
sometimes not. When ordinary water,
snch as that supplied by the New River
Company, had been passed through a
filter for several months, I found this
gas to contain a hydro-carbon. On the
contrary, when leaving spongy iron in
contact with distilled water for an equal
length of time, I failed to detect either
carbon or hydrogen in the gas. This
apparently demonstrates that the carbon
in the former case was a product of the;
decomposition of organic matter.
It is likely that the nitrogen is, in the
first instance at least, more or less con-
verted into ammonia by filtration through
spongy iron, but as ammonia is un-
questionably at the same time produced
in several other ways, I do not at present
see how to furnish an experimental proof
of that hypothesis.
Whether the ferrous hydrate formed
by oxidation of the metallic iron has any
decomposing action upon organic matter,
is a question which I have not hitherto
succeeded in answering. The final
product of the oxidation is of course
ferric hydrate. We know the destructive
action of rust stains upon even such in-
destructible organic matter as linen and
cotton fibres. It was, therefore, to be
expected, that ferric hydrate should take
an active part in the separation of or-
ganic matter from water. This led to
the following experiments.
A glass bottle, tabulated at its base,
was internally coated with a film of
ferric hydrate, by filtering water through
spongy iron, and then passing it into the
bottle without previously separating the
iron in solution. As soon as the bottle
was nearly full, it was again emptied by
a syphon arrangement, the soluble iron
being thus oxidized and precipitated at
the sides of the bottle. This was re-
peated until a sufficient deposit had been
36
VAN NOSTRAND'S ENGINEERING MAGAZINE.
obtained, showing the characteristic ap-
pearance of ferric hydrate. The bottle
thus prepared, after being filled with hay
infusion, was stoppered, and left to
stand for a couple of months, when the
color of the film gradually darkened.
The bottle was then emptied, rinsed with
water, and left exposed to the air.
After about a fortnight, the coating al-
most regained its original yellowish-
brown tint. It is thus evident that part
of the oxygen had, in the first instance,
been transferred from the ferric hydrate
to the organic matter of the hay infusion.
As any action would be much more
energetic in the nascent state of the
ferric compound, it became of interest to
study more closely the re-actions which
take place when passing water through
the spongy material.
A tabulated glass vessel was filled
with spongy iron. On allowing the
water to pass through the vessel con-
tinuously for a few days, each granule
appeared coated with ferric hydrate.
However, on stopping the passage of the
water, the color of the material which re-
mained covered with water soon became
darker, having after a few days, almost
its original appearance. I explain this
by a reduction of the coating of ferric
hydrate, by agency of the kernel of
metallic iron in each granule, the pro-
duct being some lower oxide, which in
its turn is readily re-oxidized to ferric
hydrate by the oxygen dissolved in
water. Thus the spongy iron acts indi-
rectly as the vehicle for conveying the
atmospheric oxygen to organic matter and
this continues for a long time, as on the
very top I found still a considerable pro-
portion of metallic iron, after passing
water continuously through spongy iron
for upwards of ten months. Thus there
are reducing and oxidizing agencies con-
stantly at work in the spongy iron filter,
and the several oxides of iron are present
in their nascent state.
In entering upon the chemical evi-
dence of the efficiency of those agents
which are employed or proposed as puri-
fiers of water, I regret that there should
be so little conclusive evidence concern-
ing them, excepting as to animal char-
coal and spongy iron. Whilst I cannot
hesitate to lay before you the evidence
of disinterested authorities, I am natural-
ly reluctant to refer to my own experi-
ence in judging of the merits of other
materials than spongy iron. There was
lately a chance of enlarging our knowl-
edge on this subject, when the Sanitary
Institute of Great Britain arranged for a
competitive examination of domestic
filters in connection with their exhibition
at Leamington. Unfortunately, only a
few of those invited thought fit to sub-
mit their filters to the trial, those repre-
sented comprising animal charcoal, the
peculiar shale which is employed in some
filters, and spongy iron. The committee
appointed by the institute to test the
purifying power and other merits of the
several filters consisted of Dr. Bostock
Hill, of Birmingham, county analyst;
Dr. George Wilson, of Leamington
medical officer of health: and Professor
Cameron, of Dublin. You are probably
aware that the award " for general ex-
cellence" of the Institute's medal was
made to the spongy iron filter.
Important evidence on the same sub-
ject, though also incomplete, owing to
the unwillingness of most manufacturers
to submit their filters, is to be found in
the Sixth Report of the Rivers Pollution
Commission, " On the Domestic Water
Supply of Great Britain." There we
find the result of fifteen pairs of analyses
of Thames water, before and after filtra-
tion through spongy iron, the testing
being repeated about every fortnight.
On comparing the average result of the
two last pairs of samples with that of
all samples, we find that, after the fil-
ter had been in constant action for up-
wards of eight months, the reduction of
the important nitrogenous organic
matter and of the hardness was still con-
tinuing.
I may take it for granted that the con-
clusions which have been drawn in the
report from these analyses are known to
you; they would, without doubt, have
been still more satisfactory had not the
spongy iron filter experimented upon
been one of the very first ever made.
Thus, it was of a somewhat crude con-
struction, not provided with the regulator
which has now become a feature of the
filter: thus I account for a certain irreg-
ularity in the analytical results.
Now, in the same report, there is also
exhaustive evidence as to the merits of
animal charcoal as a purifier of water.
It is demonstrated, and I think we all
THE PURIFICATION OF WATER.
37
are aware of this fact, that fresh animal
charcoal removes not only a large pro-
portion of the organic impurity, but also
of the mineral matter. However, the
report tells us the reduction of the hard-
ness ceases in about a fortnight, the re-
moval of organic matter continuing even
after six months, though to a much less
extent especially if the filter be much
used. For this reason it was found
necessary to renew the charcoal every
six months, when used for the filtration
of the comparatively pure water of the
New River Company; whilst the water
which is supplied from the Thames re-
quires the renewal of the charcoal every
three months. Unless this be done, we
are told that myriads of minute worms
are developed in the material, passing
out with the filtered water. This state-
ment sufficiently explains the final con-
clusion, but the property of animal char-
coal of favoring the growth of the low
forms of organic life is a serious draw
back to its use, as a filtering medium for
potable waters.
The chemical, part of this evidence is
more than corroborated by Mr. Byrne's
experiments. He stated, in a paper read
before the Institution of Civil Engineers
in 1867, that on passing 12 gallons of
moderately impure water through ani-
mal charcoal, over 55 per cent, of the
organic matters were removed from the
first gallon, but that this declined so
rapidly that, at the eighth gallon, organic
matter was given back to the water.
In the debate on Mr. Byrne's paper,
Mr. Chapman stated that he actually
recovered from the charcoal the amount
of organic matter which had been pre-
viously removed by it from a water.
If we compare these statements with
others which are more favorable to char-
coal, we must, I think, conclude that
under certain conditions, which are as
yet not thoroughly understood, it ap-
pears capable of giving more satisfac-
tory results. Probably this depends
largely upon the thorough burning,
without alteration, of the physical struc-
ture.
But, granted that there are no remains
of half charred flesh or fat in the char-
coal filter; that all organic matter has
been destroyed by burning; even then
we can explain the physiological results
referred to in the report, namely, the lia-
bility of favoring the growth of the low
forms of organic life. An intimate con-
nection appears to exist between these
and phosphorus, as is clearly demon-
strated by the microscopic water test
which has been proposed by Mr. Heisch.
If a minute quantity of cane sugar be
added to ordinary water, low organisms
are developed in such enormous numbers,
as to cause, in about twenty-four hours,
an opalescence, ormilkiness. Dr. Frank-
land has demonstrated that this is wholly
or partially due to the minute trace of
phosphorus contained in sugar, as he ob-
tained a similar result by adding a
variety of compounds of phosphorus in-
stead of sugar. Is it then astonishing
that animal charcoal, containing some
seventy-five per cent, of calcic phosphate,
which is by no means insoluble in water,
should produce a like effect ?
If I have succeeded in demonstrating
that fermenting organic matter is
amongst the most objectionable impuri-
ties in water, the preceding suggestions
are worth our fullest attention, as the
milkiness produced in water by sugar is
unquestionably due to fermentation. But
the objection to the use of animal char-
coal as a filtering medium for portable
water becomes still more serious, if we
assume that some of the most disastrous
epidemic disases are produced by low
forms of organic life. Can we, in this
case, a priori, maintain, that their growth
may not also be favored by animal char-
coal ? Chemical analysis is incompetent
to deal with this question, for the living
matter in water is by weight always in-
significant, as compared with the dead
organic matter. Analysis may, there-
fore, show, after filtration, a considerable
reduction of the total organic matter,
and yet those living bodies may have
enormously increased.
May I, in further support of this im-
portant point, refer you to my researches,
which you will find in the proceedings
of the Royal Society ? With a view of
testing the purifying action of spongy
iron, physiologically, I left meat in con-
tact for many months with ordinary
water, or even hay infusion, both having
been filtered through spongy iron. The
meat remained fresh throughout, if no
putrefactive agents had access to it, ex-
cepting those that might have passed
with the water or hay infusion through
38
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the filtering medium. Putrefactive
agents were, therefore, absent from the
filtered liquids. But on filtering the
same kind of water as before, under
otherwise precisely like conditions,
through animal charcoal, the meat was
putrid after a short time. It would of
course have been useless to extend the
latter experiment to hay infusion.
From these results we may draw im-
portant practical conclusions. Ferment-
ation or putrefaction are some of the
most powerful agents in destroying or-
ganic matter by converting it into a
number of gaseous and other constitu-
ents. If such fermentation be constantly
at work within a filtering medium, we
can understand what becomes of the or-
ganic matter, should it even be only
mechanically retained in a filter. But
this is different in the spongy iron filter,
looking at the preceding results. Putre-
faction being unable to effect the elimi-
nation of organic impurities, they must
either accumulate or be got rid of by
some such chemical agency as before
suggested. A constant accumulation
would necessarily soon result in a con-
tamination of the filtered water, the lat-
ter taking up organic matter from the
filtering medium, as we found it stated
in the case of animal charcoal. This be-
ing contrary to all evidence, we must
conclude that no such accumulation
takes place, but that the organic impuri-
ties are destroyed and rendered innocu-
ous in the spongy iron filter, by at least
as powerful chemical agents as fermenta-
tion and putrefaction.
You are probably acquainted with the
three reports in the Registrar General's
returns for 18*76, 1877, and 1878, on the
spongy irOn filter, and I might pass
them over, did I not wish to draw your
attention to the interesting result re-
corded in the report for 1877, that even
in times of flood, when the Thames was
unusually loaded with organic impuri-
ties of the most disgusting origin, its
water was, after filtration through
spongy iron, purified to such an extent
as to surpass the Kent water, which, from
its freedom from organic contamination,
is justly considered the standard of
purity. The organic carbon in the fil-
tered Thames water was .038 in 100,000
parts, that in the Kent water .048. Both
were equally free from organic nitrogen,
but the hardness of the filtered Thames
water was less than one-third that of the
Kent water. The filter had previously
been in use for more than a year without
change of materials. The ammonia in
the filtered water was increased to .010.
Referring to the correspondence on this
subject in the early numbers of the
Chemical News during the present year,
I maintain, that we cannot draw from
the presence of ammonia in such filtered
water any inference, which might be
more or less justified when analyzing a
natural water that has not undergone any
such artificial treatment.
By direction of the Under Secretary
for War, a trial of filters was commenced
at the Army Medical School, Netley, by
the late Dr. Parkes, and completed
about two years later by Dr. de Chau-
mont. It was found that of all filters
experimented upon, the spongy iron
filter alone yielded water in which no
living or moving organisms could be de-
tected under the microscope.
A report strongly recommending spongy
iron has also been recently made to the
Prussian War Minister by the military
authorities at Coblenz. It is based up-
on experience with a large filter during
an epidemic of typhoid amongst the gar-
rison. A cop^ of the report has been
promised to me, but as yet I have not
received it.
Lastly, a report was made at the
Somerset House laboratory, by request
of the Secretary for India, which is
throughout in favor of the spongy-iron
filter.
I have devoted so much time to do-
mestic purification of water, because, as
a rule, it is more effective than that on
a large scale before delivery of the
water to the consumer. This hardly re-
quires an explanation. Look at our
city. Its daily requirement of water, in
round figures, is 120 million gallons.
Such an enormous quantity is not easily
dealt with, moreover, only a small pro-
portion is used for drinking and cooking.
This consideration has lately led to the
proposal of two distinct water supplies,
one for drinking and cooking, and an-
other for general use. We then might
either have derived the former supply
from unexceptionally pure sources, or
we might have bestowed so much more
care and expense upon the purification
THE PURIFICATION OF WATER.
39
of the potable water. But although
this apparently would have been a satis-
factory solution of the question, I am
afraid it is fraught with great difficulties
indeed.
If that scheme had ever been carried
out, the present water supply would, al-
-most, as a matter of necessity, have been
neglected, as its purity for flushing and
the like is of no great consequence. The
quantity of water for drinking and cook-
ing alloted to each consumer by the pro-
visions of the scheme was very liberal;
but suppose the supply of pure water
had ever failed, what would have been
the consequence ? Again, I do not see
how any householder could possibly
have been prevented from using three
or four times the quantity of pure water
he was entitled to. The result must
have been inevitably an insufficiency
elsewhere. Now, in these cases, and if
by negligence or obstinacy of servants
the impure water were used for drinking,
it would have been a most serious matter
had our present supply deteriorated.
In view of the difficulty of purifying
the whole water supply, or of branching
off a separate supply for internal use, we
would at once dismiss purification on the
large scale as undesirable, and confine
ourselves to domestic filtration, if not
there again we found most serious objec-
tions. We cannot expect, for the pres-
ent at least, to reach with domestic fil-
tration the poorer classes and we have
not only an interest in their welfare as
our " neighbors," but we are person-
ally interested in it. However careful
we may be to exclude disease from our
houses, by providing a wholesome water,
disease may be spread to them from the
houses of the poor.
This leads me to a practical suggestion.
I take it for granted that in London,
and the same holds good in many other
localities, careful filtration through sand
is sufficient almost throughout the year.
Why, then, should not additional means
of purification, say through spongy iron,
or any other medium that may be found
preferable, be held in readiness, to be
used ouly in emergencies, such as floods,
or during periods of epidemics ? The
same spongy iron might thus be made to
Jast at least five or six times longer than
when continuously used, and the working
expenses would be so considerably re-
duced as to become insignificant. I be-
lieve, that, with an efficient supervision
of the water supply, this proposal might
work very well, offering all reasonable
guarantees.
A water which has never been polluted
would certainly be preferable to one
which, after contamination, is re-purified.
But where is, with rare exceptions,
water to be found which has never been
polluted ? Deep-well waters and even
spring waters are unquestionably more
or less supplied by polluted surface
water, which is purified by natural filtra-
tion. If analysis, if the microscope,
prove that artificial filtration is equally
or even more effective, if the physiologi-
cal character of both waters should prove
the same, w7e may, I think, as safely
rely upon artificial as upon natural filtra-
tion, and more so upon the former, as
the naturally purified water may fail,
whilst artificial filtration may be carried
out to almost any extent.
GAS AS FUEL.
By M. M. PATTISON MUIR.
From "Nature."
Attempts have been made from time
to time to use gas as a means for heat-
ing; these attempts have more frequently
failed than succeeded, chiefly by reason
of the mechanical difficulties to be over-
come.
It is pretty generally agreed that, on
account of the ease with which the sup-
ply of a gaseous fuel can be regulated,
the completeness with which such a fuel
can be burned, the comparative readi-
ness with which cleanliness can be main-
tained while using this fuel, and by rea-
son of its high heating power, and for
other reasons, gaseous fuel is to be much
preferred to fuel in the solid form.
The most perfect gas for heating pur-
poses would be that, the constituents of
40
VAJST NOSTR AND' S ENGINEERING MAGAZINE.
which should be all combustible, should
be possessed of high thermal powers,
and should produce, on burning, com-
pounds of small specific heat. No gas
which has yet been produced for use as
fuel completely fulfills these conditions.
Common coal-gas contains such non-
combustible bodies as carbon dioxide and
nitrogen, and among the products of its
combustion is water, a body of large
specific heat, and also requiring a con-
siderable amount of heat to convert it
into vapor. The complete combustion
of coal gas also necessitates a compara-
tively large supply of air, and this,
again, involves special mechanical appli-
ances. Nevertheless, coal-gas has been
proved to be, for certain purposes, a
cheaper, more effective, and more easily
managed fuel than eoal, wood, or other
forms of solid heat-giving material.
That steam is decomposed by hot car-
bon with the production of a gaseous
mixture of considerable heating powers,
has long been known, and several
attempts have been made to utilize the
products of this decomposition. These
attempts have met with no great success
on account of the cost of the plant re
quired to work the manufacture and of
the difficulties of the process. Long-
continued experiments have, however,
been carried on, and it would appear
from a paper recently communicated to
the Society of Arts by Mr. S. W. Davies,
that these experiments have been
crowned with a very fair measure of
success.
The great difficulty was a mechanical
one : it has been very simply overcome.
Superheated steam is produced in a coil
placed within a cylinder and is driven by
its own tension in the form of a jet into
the lower part of an anthracite fire. The
jet of steam carries with it air sufficient
to actively maintain the combustion of
the anthracite; the gases issue at the top
of the apparatus and pass into the mains.
The fire is fed from the top by an
arrangement which allows of the process
being continuous. Water is forced into
the coil under a pressure varying from
fifteen lbs. to forty lbs. on the square
inch. The whole apparatus is compact
. and simple.
The products of the decomposition of
steam by hot carbon are mainly hydrogen
and carbon monoxide; traces of marsh
gas are also formed. Could these gases
be produced free from admixed non-
combustible bodies we should have a gas
of very high heating powers. But the
temperature of the glowing carbon must
be maintained by the introduction of
oxygen, that is, in practice, by the intro-
duction of air. The problem how to in-
troduce air sufficient to keep up vigorous
combustion, and at the same time to
maintain the decomposition of the steam,
appears to have been satisfactorily
solved; but the introduction of air means
a lowering of the heating power of the
gas produced, inasmuch as four volumes
of nitrogen are brought in along with
every volume of oxygen supplied. By
passing the gas through a series of ves-
sels containing hot carbon the nitrogen
may be very much diminished in amount,
and the heating power of the gas pro-
portionally increased.
The gas produced by the decomposi-
tion of steam by hot carbon always con-
tains traces of carbon dioxide which is
non-combustible; the amount of this
compound may, however, be reduced to
three or four per cent, by regulating the
depth of the layer of hot carbon through
which the gases pass, and by maintaining
the temperature of that carbon at a high
point. But the maintenance of a high
temperature throughout a mass of carbon
can be accomplished, under the condi-
tions of the manufacture, only by intro-
ducing a rapid current of air, which
again means a dilution of the gas pro-
duced.
If, therefore, means could be found for
feeding the anthracite fire with oxygen,
a gas of very high heating power might
be produced. A supply of oxygen at a
cheap rate is a great desideratum; the
gas exists in practically unlimited quan-
tity in the atmosphere, but an easy and
successful method for separating it from
the nitrogen with which it is there mixed
is still only hoped for by the chemical
manufacturer. Were a supply of oxy-
gen forthcoming, mechanical difficulties
would present themselves before it could
be utilized in the production of " water
gas." The introduction of too small an
amount of oxygen would mean the non-
decomposition of the whole of the steam
and the cessation of the combustion of
the anthracite; the introduction of too
much oxygen would mean the produc-
GAS AS FUEL.
41
tion of carbon dioxide in considerable
quantity. But by regulating the size of
the steam jet and of the blast-pipe, these
difficulties might probably be overcome.
As the gas is now produced all danger
of explosion is removed.
The heating effect of the gas as at pres-
ent manufactured is about one-fifth that
of ordinary coal-gas, for equal volumes;
but the cost of the gas is so much less
than that of coal-gas, that a given
amount of heating work may be done —
according to the figures given in the
paper referred to — by using the new
gas, with a saving of from one-third to
two-thirds of the expenditure which
would be involved were coal-gas em-
ployed.
Although the new gas is not perfectly
adapted for the purposes for which it is
to be used, yet there can be little doubt
that we are now a step, and a very con-
siderable step, nearer the final solution
of the problem. Doubtless improved
furnaces, and improved apparatus gen-
erally for burning the improved fuel
will be introduced.
The production of a cheap gaseous
form of fuel is a great gain ; so also is
the invention of a means whereby the
large stores of anthracite coal in this
and other countries can be utilized.
Of all the forms of carbon experi-
mented with in the production of the
new gas, anthracite was found the best.
Anthracite is difficult to burn; the ordi-
nary forms of furnace do not admit of
such a complete oxidation as is required
in order to maintain the combustion of
anthracite. But the blast of air carried
into the gas generator of the water-gas
apparatus by the steam jet insures the
presence of a large quantity of oxygen,
and therefore the combustion of the
anthracite. Whether a simpler means
could not be adopted for the combustion
of anthracite is a question worthy of
consideration. That a steam jet can be
thrown into an ordinary furnace charged
with anthracite, and the combustion of
the coal be thereby insured, has been
shown to be possible. Nevertheless, the
production of combustible gas from the
anthracite is to be preferred, for many
reasons, to the consumption of the solid
fuel.
The fact that we shall soon probably
be in a position to make use of our stores
of anthracite, is one of very considerable
importance from an economic point of
view. In possessing large quantities of
anthracite we possess a valuable com-
modity, but if we cannot realize a use
for that commodity it ceases to be a
source of wealth to us.
Further, large quantities of anthracite
are known to exist in some of the British
Colonies and in the United States; the
utilization of these would mean an in-
crease in the commercial enterprises
owned by Englishmen abroad, or sup-
ported by English capital; it would also
probably imply an increase in the ton-
nage of shipping, and would thus tend
to increase our " international wealth."
Whether it be regarded from the point
of view of the chemist, or of the econo-
mist, the introduction of a cheap gase-
ous fuel manufactured from anthracite,
marks a point of no little importance in
the advance of manufacturing industries.
The experiments detailed in the paper
by Mr. Davies show that the new gas is
especially adapted for use in cooking
operations in large private establish-
ments, in clubs, hotels, barracks, &c. It
is known that cooking can be more
cheaply and more rationally conducted
with the aid of gaseous than of solid
fuel; if the new fuel does all that it
promises to do, judging from the actual
trials already made, its introduction will
be welcomed by the artistic cook no less
than by the scientific chemist, and by
the political economist.
Good strong blown glass tumblers are
being delivered into English ports from
America for 8d. per dozen, and good
hexagonal and octagonal cut Dutch
tumblers for 4s. 8d. per dozen. The
above fact relating. to importation from
the United States, from whence but re-
cently nothing of the kind was exported,
is illustrative of the keen competition in
manufactures generally, and in particular
shows the necessity for the abolition of
the English glass blowers practice of
working but four days per week, a
practice maintained by the glass blowers'
guild, and one which prevents the con-
tinuous operation of the costly furnaces
and plant in a glass works. A smaller
profit on most English goods will have
to be accepted in the near future.
42
VAN NOSTRAND'S ENGINEERING MAGAZINE,
STEAM ENGINE ECONOMY— A UNIFORM BASIS FOR
COMPARISON.
By CHAKLES E. EMERY, M. E.
From the Transactions of the American Society of Civil Engineers, March, 18T8.
In writing a general report on the
exhibits referred to the Judges of Group
XX, Centennial Exhibition, the writer
compared the facts available in regard
to the economy of steam engines of
various kinds, on the uniform basis that
the boiler is capable of absorbing 10,000
heat units per pound of coal consumed.
This corresponds to an evaporation of
8.99 pounds of water at 80 pounds
pressure, 9.03 pounds at 60 pounds
pressure, or 9.08 pounds at 40 pounds
pressure from a temperature of 100° in
each case. This evaporation is higher
than is usually obtained, but has been
so much exceeded in practice* that it is
not considered too high for a basis of
comparison. The basis moreover enables
the duty of pumping engines and other
steam machinery to be ascertained and
expressed in a very ready and conven-
ient manner. Ten thousand heat units
per pound of coal is equivalent to one
million heat units per 100 pounds of coal
and as the duty of pumping engines is
conventionally expressed in millions of
foot pounds per 100 pounds of coal it
follows on the basis presented that the
number of foot pounds per heat unit rep-
resents also the number of millions of
foot pounds duty per 100 pounds of coal.
The performance of all kinds of steam
engines may be readily compared on this
basis. The simplest application is in
testing vacuum pumps, the duty of which
may be readily ascertained by noting the
height of lift, and the initial and final
temperatures of the water lifted. All
the heat of the steam not expended in
work enters the water, and the work
performed lifts the same water. The
difference in temperature gives very
nearly the number of heat-units imparted
to each pound of water lifted, and each
pound of water so heated is lifted a cer-
tain number of feet high, so the result
may be expressed readily in foot-pounds
per heat-unit, which, as before stated,
equals also, on the basis presented, the
number of millions of foot-pounds duty
for 100 pounds of coal. For ordinary
comparisons the number of millions duty
equals the lift, divided by the difference
between the initial and final tempera-
tures of the water. For more accurate
computations, the divisor should be in-
creased by the number of heat-units ex-
pended for work per pound of water
lifted, which equals the height divided
by 772. The height preferably should
be calculated from the indications of a
pressure-gauge at the bottom of the dis-
charge-pipe, so as to include frictional
resistances. If D = duty in foot-pounds
per 100 pounds of coal, H = the height
of lift per gauge, and t and T = the
initial and final temperatures respective-
ly, then
1,000,000 H
D:
T— 2-K0013 H.
* See examples at page 75 of the report referred to.
Arrangements have been made by the
writer to use the same basis in testing
pumping-engines, by discharging water
from the hot wrell into the suction of the
main pumps, and rioting with delicate
thermometers the resulting increase of
temperature of the water lifted
A vacuum-pump tested by the writer
in 1871 gave a duty, on the above basis,
of 4T\ millions; one tested by Mr. J. F.
Flagg, at the Cincinnati Exhibition in
1875, reduced to the same basis, gave a
maximum duty of 3-^ftj- millions. Several
vacuum and steam pumps tested on this
basis, at the suggestion of the writer
about two years since, gave duties re-
ported as high as 10,000,000 to 11,000,000,
the very small steam-pumps doing no
better apparently than the vacuum-
pumps, which is by no means surprising.
Elaborate experiments made with steam-
pumps at the American Institute Exhibi-
tion of 1867* showed that average-sized
steam-pumps do not, on the average,
utilize more than 50 per cent, of the in-
dicated power in the steam- cylinders,
* See Report of Messrs. Holmes, Selden, and Emery,
Judges, etc., Transactions American Institute, 186T-68.
STEAM ENGINE ECONOMY.
43
the remainder being* absorbed in the
friction of the engine, but more particu-
larly in the passage of the water through
the pump. Again, all ordinary steam-
pumps for miscellaneous uses require
that the steam-cylinder shall have 3 to
4 times the area of the water-cylinder to
give sufficient power when the steam is
accidentally low; hence, as such pumps
usually work against the atmospheric
pressure, the net or effective pressure
forms a small percentage of the total
pressure, which, with the large extent of
radiating surface exposed and the total
absence of expansion, makes the expendi-
ture of steam very large. One pump
tested by the writer required 120 pounds
weight of steam per indicated horse-
power per hour, and it is believed that
the cost will rarely fall below 60 pounds;
and as only 50 per cent, of the indicated
power is utilized, it may be safely stated
that ordinary steam-pumps rarely require
less than 120 pounds of steam per hour
for each horse-power utilized in raising
water, equivalent to a duty of only
15,000,000 foot pounds per 100 pounds
of coal on the same basis adopted for the
vacuum-pumps. With larger steam-
pumps, particularly when they are pro-
portioned for the work to be done, the
duty will be materially increased.
Ten thousand heat units per pound of
coal represent an ultimate efficiency of
only (10,000X100-^14,500*=) 69 per
cent, of the calorific value of anthracite
coal, so that ordinarily more than (100
— 69 = ) 31 per cent, of the heat in the
fuel is carried to waste up the chimney.
A still greater loss is, however, experi-
enced in utilizing the steam for the pur-
pose of work in the engine. The
mechanical equivalent of one heat-unit
is 772 foot-pounds, which, on the basis
referred to above, corresponds to a duty
of 772 millions of foot-pounds per 100
pounds of coal. The most economical
steam-engines, for instance pumping-
engines of approved types, utilize in the
steam-cylinder only about 130 millions,
on the same basis, equivalent to an ulti-
mate efficiency of (130X100-^-772=)
16.84 per cent, of the heat in the steam,
and but (16.8-4X.69 = )11.62 per cent, of
the calorific value of the fuel. The
principal reason for this is that the ex-
haust steam necessarily carries to waste
the heat required to maintain it in a
vaporous state at the tension due to the
back pressure. This, under the most
favorable circumstances, forms the larger
proportion of the total heat of the steam,
and reduces the opportunities for secur-
ing economy within small limits com-
pared with the theoretical limit, although
the differences between the performances
of different engines are great when com-
pared one with another.*
Means for securing economy in steam-
engines may be divided into two classes,
viz., those of a mechanical nature and
those which influence the thermal con-
ditions. As to the first, the necessity of
securing tight pistons and valves, ample
area of cylinder passages, reduced clear-
ances, etc., are well understood, also the
incidental advantages due to a certain
degree of compression. Those of the
second class act to reduce the cylinder
condensation, and include high speeds of
revolution, steam superheating, steam-
jacketing, and the compounding of en-
gines. High speed of revolution (which
does not necessarily imply high piston
speed, as generally understood) secures
economy, by reducing the time in which
the transfers of heat to and from the
steam and inclosing walls must take
place, f
Superheating the steam has experi-
mentally proved effective for moderate
rates of expansion, in wThich the original
* la view of discussions in progress at the date of
writing on the proper details of a theoretically perfect
steam-engin j, it is p oper to mention that in the year
186S the writer designed and partially constructed a non-
exhausting experimental eugine in which the steam, after
expansion in the cylinder, was to be circulated through
another vessel, to withdraw the water due to the per-
formance of work; the dry steam was then to be returned
to the cyliuder and compressed, which it was expected
would require less power than the expansion would fur-
nish, aud sufficient steam only be received from the
boiler to supply that condensed for work. A demonstra-
tion of the correctness of the principle only wa,s intended,
the power expected being so small that the experimental
engiue was to be connected to another to keep it iu motion.
Before the apparatus was completed the funds were
diverted to objects of greater immediate necessity, and the
subject is mentioned only as indkating'the general princi-
ple upon which a theoretically perfect steam-engine may
be constructed. See description of the apparatus in arti-
cle on the " Theoretical Ste mi-Engine," Scientific Ameri-
can Supplement, Aug. 18, 1S77. See also Prof. Thurston's
calculations on a similar subject iu Journal of the Frank-
lin Institute, Oct., Nov., and Dec, 1871.
• The calorific value of anthracite coal is usually con-
sidered to be that of the carbon element or 14500 heat-
units.
t The value of this saving was
writer for the Novelty Iron Works,
determined by the
. Mr. Horatio Allen,
President, in the year 1868, and embodied in a series of
tables showing the relative power and economy of differ-
ent sizes of steam-engines, which tables were afterwards
published Jby Prof. W P. Trowbridge, the former Vice-
President of the company.
44
van nosteand's engineeking magazine.
temperature required to maintain the
gaseous condition of the steam to the
point of release was not too high to pre-
vent proper lubrication. Mr. Geo. P.
Dixwell, of Boston, Massachusetts, has
applied a thermometer to a steam cylin-
der, by inspection of which it is possible
to regulate the temperature so as to pre-
vent injury to the metal surfaces. The
great difficulty is, however, to secure a
permanent and reliable superheating ap-
paratus. Steam-jacketing has to a limit-
ed extent advantages of the same kind
as superheating, and involves no serious
difficulties in management. The jackets
are most effective on long cylinders of
small diameter. In experiments with
United States Tevenue steamers, herein-
after mentioned, the economy of a steam-
jacket on a comparatively short cylinder
was found to be eleven to twelve per
cent.
Compound engines, in addition to ad-
vantages of a mechanical nature, in bet-
ter distributing the strains and rendering
more uniform the rotative efforts, serve
also to reduce cylinder condensation by
the distribution of the differences of
temperature between two cylinders. The
radiation to and from the steam and its
inclosing walls increases more rapidly
than the difference in temperature, so
that the aggregate loss, when the differ-
ence of temperature is divided between
two cylinders, is less than when it all
occurs in a single cylinder*. Moreover,
the heat imparted to the exhaust steam
by the metal of the first cylinder is
available for wTork in the second, and the
low-pressure piston acts as a screen be-
tween the high temperature in the small
cylinder and the low temperature in the
condenser.
It is still strenuously denied by many
that greater economy can be secured
with a compound engine than with a
long-stroke single engine using the same
steam pressure. There are coasting
steamers of similar size running regularly
in the United States using both types of
engine, with, it is claimed, substantially
the same results; but the boilers for the
single engines are evidently the more
economical, making an accurate com-
* See article by the writer in American Artizan,
March 8th, 1871. See also this Magazine, for May,
1871.
parison impossible. Strictly compara-
tive experiments have, however, been
made by Chief Engineer C. H. Loring,
U.S.N., and the writer with engines of
different kinds in the steamers of the
United States Revenue Marine, and by
the writer with some of those of the
United States Coast Survey.*
The revenue steamers were of the same
size and the boilers \erj nearly identical.
In one steamer was a compound engine
with steam-jacketed cylinders; in another,
a long-stroke, high -pressure condensing
engine (cylinder not jacketed) ; in
another, an ordinary low-pressure engine
(cylinder not jacketed); and in still
another, a high-pressure condensing en-
gine with a jacketed cylinder. The com-
pound engine showed a saving of 12 to
16 per cent, compared with the best per-
formance of either single engine when
operated at the same steam pressure. It
is believed that substantially the same
differences will be found in all cases
when equally good engines of both types
are compared. The performance of a
short-stroke compound engine may be
equaled or even excelled by that of a
long-stroke single engine, on account
simply of the difference in clearance
spaces and the superior efficiency of the
steam-jacket in the latter case, but by
making the compound cylinders in the
same form they should still show an ad-
vantage. In practice, the economy of
marine compound engines is greater than
above mentioned, for the reason that the
high steam pressure is better maintained
with them by the engineers than when
single cylinders are used with high rates
of expansion, causing difficulties in man-
agement.
The following table shows in line 1
the performance of one of the Leavitt
compound beam pumping-engines, at
Lawrence, Massachusetts, and in line 2
that of the engines of the Hush, one of
the revenue steamers previously referred
to :
* See article by the writer on " Compound and. Non-
Compound Engines," Transactions American Society of
Civil Engineers, vol. iii. p. 68, 1875; Journal of the
Franklin Institute, Feb. and March, 1875 ; Engineering
(London), Jan., Feb., and March, 1875; Proceedings of
Institution of Civil Engineers (British), vol. xT. p. 292, and
vol. xli. p. 296 ; also report of trial of United States reve-
nue steamer Gallatin, Journal of the Franklin Institute,
Feb., 1876, and vol. xxi., Engineering, 1876.
STEAM ENGINE ECONOMY.
45
6
a
.2
'oS
a
S3
o
o
ft
h3
Pressure
d to Large
Under.
CO
8-i
H3
o ft
ej-l
O
™6
pa
ft
21
s
O
'■§1
O
ft
O
Water per Indi
Horse-Power
Hour.
a
1*
ft
ft
<1
O
.2
p
5
5
03
o
C72
>
M
o
Mean
referre
Cy
Inches.
Inches.
Inches.
Feet per
Minute.
Pounds.
Pounds.
1
90
13.5
18
38
96
16.27
260.3
22.15
196.4
14.02
2
70
6.22
24
38
27
70.84
318 8
24.48
266.6
18.38
The comparison is very interesting.
In both engines the larger cylinders are
of the same diameter, but the difference
in the duty for which the engines were
designed required great differences in
other proportions and in all the details
of construction. In the pumping-engine
for use on land there were no restrictions
as to weight and space, so a compara-
tively long stroke could be employed
and the connections made through a
beam. The marine engine had, how-
ever, to be located in a small vessel, and
was therefore directly connected and
proportioned accordingly. Yet the long-
stroke engine was run with so much ex-
pansion and at so slow a speed as to de-
velop less power than the smaller one,
and the latter was less economical, on
account of the lower steam pressure and
rate of expansion and the relatively
greater proportion of waste room in the
cylinder, incident to the necessary use of
ordinary slide-valves. The engine of the
Hush was, however, more economical
than the ordinary stationary compound
engines used for manufacturing purposes,
as the latter, according to published re-
ports in the engineering journals, require
the evaporation of not less than twenty
pounds of water for each indicated
horse-power. The Lawrence engine
contains all well-known means for secur-
ing maximum economy of steam, and it
is probable that few if any engines are
working with greater economy in respect
to the indicated power. The perform-
ance is, however, much below that given
by calculation when all the conditions
are taken into consideration, other than
the slight distortion of the theoretical
indicator diagram found in practice and
the important loss due to cylinder con-
densation.
In an engine using a total pressure of
(90 + 14.7 = ) 104.7 pounds, expanded
13.5 times in a cylinder, with clearances,
etc., equal to .02 of the displacement, the
calculated cost of one horse-power per
hour, or 1,980,000 foot-pounds, should be
only 8.12 pounds of water evaporated
from the initial pressure, on the basis
that the curve of expansion is hyper-
bolic, and that the consumption of steam
equals the volume at the initial pressure
required to fill the cylinder to the point
of suppression, plus that condensed for
the 'total work. With a pressure of 100
pounds above the atmosphere, and an ex-
pansion of twenty times, there should
be required on same basis the evapora-
tion of only 6.00 pounds of water per
indicated horse-power per hour. It is
probable that the practical results ob-
tained with the latter pressure and ex-
pansion would be little or no better than
those from the Lawrence engine, on ac-
count of the greater cylinder condensa-
tion due to the increased expansion.
The above-calculated performances,
and the practical results obtained with
engines and other steam machinery of
various kinds, is shown in the accom-
panying table, in connection with the
relative efficiencies obtained by consider-
ing the heat units in the steam and the
calorific value of the fuel. The table
and a portion of the above are from the
report previously mentioned and the
references are to pages therein :
46
VAN NOSTRAND's ENGINEERING MAGAZINE.
Description.
a
<o
o
Si
OQ
2
a
<fl
53
a
u
X!
Ph
H
B
o
o3
<u
o
OQ
"o3
«
Comparative Results on Basis that
10,000 Heat-Units are imparted to
Water per Pound of Coal. See pp.
21 and 115. § Calculations based on
a Temperature of Feed of 100°.
IS
OO ^
ffl iTfafl
A
•^ o
§^
o3 o
a^ o
»^.-£
'3 Jo
«a o <u
53 g *
PhS
«
&0 o3
a • ©
=4h a
■S* S °
a.SPn
fi5o
3^3
10
11
12
Calculated performance.
Maximum
Calculated performance (see
page 120)
Calculated performance
Lawrence compound beam
pumping-eneines
U.S. Revenue steamer Rush,*
compound engine
U. S. Revenue steamer Galla-
tin,* vertical cylinder with
steam-jacket
U. S Revenue steamer Dex
ter,* vertical cylinder with-
out steam jacket
U. S. Revenue steamer Dal-
las* vertical cylinder with-
out steam-jacket
U. S. steamer Mackinaw, f in-
clined cylinder without
steam-jacket
U. S. steamer Mackinaw,
steam superheated
Non condensing engine, with
governor cut off:}: (st. jacket)
Non - condensing engines,
regulated by throttle
100
90
89.4
69.2
67.2
67.1
32.0
49.0
52.0
81.7
20
13.5
13.7
6.22
4.19
3.49
3.13
2.2
3.2
5.0
6.005
8.122
14.019
18.384
21.48
23.905
26.945
30.306
22.725
25.482
772.0
295.2
218.6
126.7
97.03
1.00
.382
.283
.164
.126
83.08 i .108
74.66
66.91
59.16
78.83
69.81
30 to 45
.097
.087
.077
.102
.090
04 to. 06
.690
.264
.195
.113
.087
.074
.067
.060
.053
.070
.062
03 to. 04
13
14
15
16
17
Pumping- engines
Steam-pumps. Large size proportioned for the work to be done
Steam pumps. Small sizes for ordinary uses. See page 22 §
Vacuum-pumps. See page 21 §
Iujectors when used for lifting water not required to be heated. See page
30 to 110
15 to 30
8 to 15
3 to 10
2 to 5
* See references in foot-note, page 119, and page 44 of this No.
t See vol. ii, Isherwood's Experimental Researches in Steam Engineering, pp. 77-116.
t American Institute Reports, 1869-70, 1870-71.
§ General Keport of the Judges of Group XX, Philadelphia International Exhibition. Lippincott & Co., Phila.
ACCURATE NAVIGATION.
47
ACCURATE NAVIGATION.
By Captain MILLER.
From " The Nautical Magazine."
There are many non-nautical critics,
learned as well as unlearned, who take it
for granted that navigation as a perfect
science is always available to the navi-
gator. They seem to think that under
all circumstances he has simply to work
out a few problems, which they suppose
can be done at any time, and if done cor-
rectly and properly applied must neces-
sarily lead to infallible results. Not-
withstanding the apparent blunders, the
numerous casualties, and the pile of evi-
dence to the contrary, that continually
come to light through our Courts of In-
quiry, these persons comment as flip-
pantly on any particular case of casualty
as though there were no reason why a
ship should not arrive at her destination
as accurately as a railway train, which,
starting from one end of the kingdom,
runs up to its terminus at the other
within a foot of the platform.
Unfortunately for the value of these
comments, there are no rails laid over the
seas, and until this is actually achieved
ships will continue to deviate from
straight courses. As Nature is said to
abhor a vacuum, so ships in their courses
seem to abhor being kept to perfectly
straight lines. All that science does for
the navigator is to aid him occasionally;
occasionally, I say, because science in
her attendance on him is very whimsical,
being present only when her assistance
is least required, and invariably being
absent when her assistance is most need-
ed. When, for example, the navigator
has the full use of vision and can see
everywhere around him, when through
having the use of this vision there is no
risk of his running his ship into danger,
and navigating her is comparatively an
easy process, then science, with her
brightest smiles, is always present, ready
to overwhelm him with the tender of her
innumerable problems to verify his posi-
tion. But when, having to run for some
iron bound coast, the weather thickens
for some days previous to his reaching
it, and wind and sea press and heave the
ship an unknown amount from her track,
when all is thick, dark, and dreary, and
vision altogether fails, when the ship
may be said to be running through a
sort of " valley of the shadow of death,"
where then is science with all her bright
smiles and tenders of assistance ? These
are the times when the navigator most
needs her presence, but these are the
times when she always absents herself,
and leaves no other assistance, to aid him
in his most difficult and delicate work,
than that assuming and guessing old
pilot called " dead reckoning."
I wonder why our ancestors called this
old pilot dead. He is certainly not yet
dead, for we have him now piloting ships
in these days. He still has sufficient
life to undertake, in the absence of sci-
ence, to pilot ships to their destination.
He is, however, very old and very un-
suitable for the times, his range of vision
is far too small for these go-ahead days
— he was always very near and weak-
sighted at best, but he got on very well
in his younger days with our ancestors,
whose ships were slow, and time with
them was no very great object. With
them he had always ample time at his
command, and he took great care to
make every use of it, for when he could
not see and became a little uncert iin of
his position, he would stop. Stopping in
those days was neither a fault nor a
danger, so he stopped for every shadow
of a doubt. By this expedient he could
easily keep what perceptions he possessed
well in hand, but he cannot now resort to
this expedient, the times will not admit
of it. Speed, speed is the great demand
of the age. He often therefore loses
control, becomes bewildered, and leads
ships with all on board frequently to
disaster and death. If it was in this
sense that our ancestors called him dead,
it is an appropriate name for him, for his
piloting leads so very often to fatal
disaster. Nevertheless, this untrust-
worthy old pilot is all the assistance the
navigator has to aid him whenever sci-
ence hides her face, and unfortunately
for our climate she does this for many
days together, and far too often for the
interests of life and property. Some-
48
VAN NOSTRANJTS ENGINEERING MAGAZINE.
times thick weather sets in 500 or 1000
miles to the westward of the Channel,
and continues until the navigator either
gropes his way to his destination, or
adopts the " Westminster Abbey or
Victory" principle; depends on dead
reckoning, and runs for it regardless of
consequences. * Both of these principles
have their followers, and the latter,
strange to say, often succeeds, though
there is no basis of certainty in the cor-
rectness of any of their calculations.
Their figures and problems may indeed
be perfect, but unfortunately " dead
reckoning " is not simply a question of
figures, it is made up also of a number
of assumptions and guessings, none of
which in thick weather can be checked.
In the first place, no helmsman can
steer a course accurately; some steer
much better than others, but the best
cannot conn the ship as though she were
rnnning on rails. The course is given to
a quarter of a point, sometimes to a de-
gree, and the seaman simply makes the
best use he can of it. But much uncer-
tainty surrounds even the best perform-
ance when the ship is running for land
in and after continued thick weather,
no matter how smooth the sea; and
naturally in proportion as the sea is
rough will this uncertainty be aggra-
vated. The science of navigation, as
yet, does not supply the navigator with
any instrument that will register the
amount of deviation from a straight
course, made in consequence of defective
steering, and the question therefore is,
when the light of science is absent, and
vision as a preventive to disaster useless,
what margin of error is to be allowed
for it, and which way, whether to the
right or to the left ? But science is ab-
sent, she does not answer this question;
and as for " dead reckoning," he is too
stupid to give it even a thought; in this
case, as in all cases, excepting those for
which he allows lee-way, he assumes that
the course given to the helmsman is
" made good," and all his calculations are
based on this assumption.
Besides defective steering, science has
left the navigator, in an iron ship, to
find his way in thick weather as best he
may, with a very defective compass.
This is the case whether it be an uncom-
pensated standard or one said to be ad-
justed. What a fraud on the under-
standing and practical experience of the
navigator it is to say, because a number
of magnets are screwed down to the
deck round his compass, acting at cross
purposes with each other, that therefore
his compass is adjusted. In spite of any
number of fixed magnets that can be
placed round it, it is not adjusted. It is
only a rude attempt at adjustment, and
a very delusive one also.
But let us consider the value of the
standard compass towards making an
accurate course, as this is the one, doubt-
less, that the navigator will employ.
Now the compass-card, with its magnetic
needles, somewhat resembles the fly-
wheel of machinery, with this difference,
that, instead of being expected to revolve
on its axis, it is its duty to stand per-
fectly still, while its axis and the ship
revolve under it. If the wheel of the
machinery is perfectly balanced, then
there will be no disturbance of its regular
action by the law of gravitation, and if,
with the compass, there is no magnetic
disturbance, the card will stand quies-
cent, while the ship is supposed to re-
volve round and round under it. Of
course in this experiment there will be
a slight drag of the card, but this will be
the same on all points alike, and will
not, after the ship's head has passed the
first point, interfere with its quiescence.
If the machinery again is imperfectly
balanced then the action of the flywheel
will be very irregular, and there will be,
in compass language, gravitating dis-
turbance of its action, sometimes making
it questionable whether the machinery
will turn over its center. This irregu-
larity is usually compensated by attach-
ing in its proper place a balance weight
to the wheel. But let us suppose this
machinery left to work without this
balance weight. The irregularities then
occurring in each revolution will serve
to illustrate the irregularities of the
action of an uncompensated compass.
As the ship revolves round and round,
the card instead of being quiescent will
have motion, at one point of the ship's
revolutions its north will be drawn two
points or more, according to the amount
of disturbance, to the east of the magne-
tic north, and at another it will be drawn
a corresponding amount to the westward
and there will be, as in the revolutions
of the flywheel, no uniformity in its
ACCUKATE NAVIGATION.
49
action. At one point of the ship's revo-
lutions the changes will be slow and at
another fast, and when, like the flywheel
it is turning over its center it will ap-
pear to stop, and when at another point
it will get over a number of degrees with
a jump. All this takes place with an
upright ship, but when she heels over all
the irregularities of its action are much
increased. The Liverpool Compass Com-
mittee many years ago stated that the
heeling in some ships would have an
effect on the compass to one and a-half
degrees for every degree of heel, and yet
few if any ships have ever had this dan-
gerous source of disaster compensated.
This, however, can excite no astonish-
ment when it is remembered that all
attempts to compensate the other
sources of error, with even an upright
ship, have hitherto failed. How there-
fore'can an accurate course be expected
from such a defective instrument?
Nevertheless, "dead reckoning" when
running for land in thick weather has
nothing better to make a course and to
turn unseen points.
The next thing to be considered is the
force of wind and heave of the sea act-
ing on the ship at right angles to her
course. Here again science in her
absence leaves behind no instrument
with the navigator with which he can
register the amount of broadside pressure
and heave of the sea, or the amount of
deviation from a straight course that
these will give rise to. In this case also
the navigator is left exclusively to that
guessing old pilot "dead reckoning"
again.
"Dead reckoning" notices broadside
pressure, and makes an allowance for its
influence under the name of "lee way."
It does not, however, cost him any hard
thinking to arrive at the amount to be
allowed. With him, there is no great
difficulty in obtaining it; one, two,
three, or more points, according to his
glance at the weather, is arrived at with
a bound and a jump. There is nothing
to check his guessing, nothing short of
actual disaster, and should this occur,
the blame and consequences fall exclu-
sively on the navigator; they in no way
affect him, and so he goes on guessing
and guessing the thousands upon thou-
sands of deviations from straight courses,
which are continually occurring, the
Vol. XIX.— No. 1—4
fallacy of which only those ships that
meet with disaster ever bring to the
light, and this he will continue to do
until science finds out some more worthy
pilot to leave with the navigator in her
repeated long intervals of absence from
him, or otherwise finds out some practi-
cal and more satisfactory means than
has hitherto existed for the navigator to
check all his assumptions and guessings.
Then there may be a drain of current
acting at right angles with the ship's
course, for who, at any time, can say
that the surface waters on any part of
the globe, at the time he is navigating
them, are without movement and at per-
fect rest. " Dead reckoning " takes it
for granted that where no current is
noticed and marked on the chart as ex-
isting that there never has been any, and
that there never will be, as he also takes
it for granted that where a current is
marked it is always running, and will
ever continue to do so, and at the rate
indicated. But even in well-known cur-
rents, such as the Gulf stream, on ac-
count of their variableness and the con-
tinual change of the ship's position,
" dead reckoning " in his allowance for
them is likely to be as often wrong as
right. Such a current as the Gulf
stream in its axis may run with some
degree of uniformity, allowing for sea-
sons and weather, but it certainly does
not anywhere else within its marked
limits.
Again, known currents with a velocity
of one, or a half, knot, are marked on
our charts, but are there no currents
running from twelve to one mile per
day? Certainly there are, for it may be
questioned whether the surface waters
are anywhere quiescent for any time to-
gether. Ought it, therefore, to surprise
an3rone, even where no current is marked,
for a ship to be carried in a day's
run six or more miles from her track,
may be at right angles with her course
by this one subtle agent alone.
Then there is the common log to
measure the distance run. What a rough
instrument it is on which to stake the in-
terests of life and property when run-
ning for land in continued thick weather !
When its character is considered, the
amount of intelligence at command to
heave it, the influences surrounding it to
produce changes in its revelations, and
50
VAN nostrand's engineering magazine.
the difference of speed maintained in the
interval of the two hours in which it is
generally thrown, three per cent, margin
for error would be the minimum allow-
ance that could be made for a day's run
of, say, 300 miles. Here, therefore, in
one day, as the error may be over or
under, is an uncertainty of eighteen
miles. And yet, after all, the common
log is more reliable than the patent. The
ordinary lead descending in the water
gives results in conformity with its
theory, but the patent log towed on the
surface water is very uncertain in its re-
sults and baffles all -calculations, as no
rate can be fixed to it; at one time it is
over, at another time under, and all at-
tempts to fix a percentage of rate, either
one way or the other, utterly fail. In a
steamer its results are very variable, and
its changes are as frequent as those of
the weather on which it appears to me in
a great measure to depend. "Dead
reckoning," however, has nothing better
than these logs to measure the distance
run, and when having to turn unseen
points of land, some accuracy is neces-
sary, in order to avoid danger on the one
side and bewildering dead reckoning on
the other, consequent on running in
thick weather out of his intended track.
When all the difficulties connected with
accurate navigation in thick weather are
considered, and the many disasters which
that deceiving old pilot, " dead reckon-
ing," has led to, coupled with the severity
with which the navigator has been visited
for only a misplaced confidence in him,
it would only be fair that " dead reckon-
ing " should be visited with some of the
blame and have his certificate suspended
also.
When all these things are considered,
may not the navigator very appropriately
say to science, who never seems at rest,
but constantly at work finding out new
and simpler methods to aid him in her
presence to verify his position, " Enough,
enough; where thou art present our path
is illuminated with thy light; we have
no difficulty then to contend with. It is
only in thy absence that our difficulties
commence, and these increase in propor-
tion to the length of it. Canst thou not,
considering all the interests that are at
stake, leave with us some small ray or
glimmer of thy light in thy sometimes
long absence from us. It is well-known
to thee that ' dead reckoning,' who is thy
first offspring, has grown old and un-
trustworthy for these ' go-ahead ' times.
It is well known to thee that he has not
made one single step of advancement to
meet the requirements of this progressive
age, and it is also well known to thee
that on account of his great age he in-
spires in the inexperienced navigator a
certain veneration and false confidence
which too often leads to disaster and
death. It is thy province to grapple
with difficulties. In this almost untouch-
ed field there is ample room for the full
exercise of all thy great powers. Leave
with us, therefore, in thy absence some-
thing more consistent with the demand
of these times of rapid transit, than that
blundering old pilot, * dead reckoning.'
Every navigator who aims at and loves
accuracy, whether in narrow seas or in
the broad ocean, will hail with satisfac-
tion every new invention which in any
way contributes towards its attainment,
or any that will check the assumptions
and guessings of "dead reckoning."
Two instruments have recently been
brought out, the one contributing largely
towards making an accurate course, and
the other to check the deductions of
dead reckoning. I allude to Sir William
Thomson's patent compass and patent
lead. The former of these instruments
if it does not enable the navigator to run
his ship as though she were running on
rails, at least it enables him to run
nearer thereto than anything that has
yet been supplied. From the time that
the Astronomer Royal, in 1854, laid down
the true theory for producing perfect
compensation of an iron ship's compass
until Sir William Thomson's compass
was invented, it has not been attained.
During this long interval I have utilized
every opportunity, and tried every im-
aginable experiment with the ordinary
compass to attain it, but owing to the
weight of the card could not succeed in
correcting the quadrantal deviation. The
chain-boxes, fitted with chains that were
generally attached to the binnacle for
this purpose, had no effect, and the piles
of chain that I used to apply in my ex-
periments gave no appreciable effect
either. I conclude, therefore, that with
the old compass card, owing to its
weight, to correct its quadrantal deviation
is impracticable.
ACCURATE NAVIGATION.
51
Sir William Thomson gets over this
difficulty by inventing a card, so light in
its construction that two iron hollow
globes about eight inches in diameter,
properly placed, make the correcting of
the quadrantal error possible. With
this card it can be even over-corrected,
consequently it is a simple matter re-
quiring no more scientific knowledge
than is necessary to rate a chronometer,
or adjust a sextant, to produce a really
compensated compass. The advantage
of all this towards making an accurate
course must be apparent. Like a per-
fectly balanced fly-wheel of some ma-
chinery, it becomes uniform in all its ac-
tion. While the uncompensated or
partly compensated compass, whether
liquid or otherwise, when the ship is
running before the big seas of the At-
lantic, is all wandering, Sir William
Thomson's compass is quite steady. It
is therefore quite an acquisition and
most helpful towards making an accu-
rate course, and more especially if the
helmsman has it to steer by.
The neglect to heave the lead has led
to much disaster, and many certificates
have been suspended for it. It is gen-
erally taken for granted that it is a very
simple process, and that there is not the
shadow of an excuse for not constantly
heaving it when near land. In fact
many navigators have been regarded as
idiotic for not keeping it constantly
going, but it appears to me this state of
idiocy can be reached on the other side.
Going out as a hired transport on the
Abyssinian expedition I was made, by the
transport officer, to heave the lead going
out of the Birkenhead dock gates. In
the Royal Navy the lead has to be cast
whether of use or of no use. It is a rule
of the service, and must be carried out.
There is in all this no extravagant de-
mand, for the number of men there un-
der command makes it an easy duty, and
they can afford to expend labor where
there is only a very remote chance of its
being of any use. This is not so in the
merchant service. The amount of labor
at command there does not admit of its
being expended on work that is not ap-
parent will be of some service. As a re-
sult of their training, Royal Naval men
too often judge harshly the shortcomings
of the merchant service; they forget that
no amount of tyranny that can be re-
sorted to can obtain from a limited crew
the same attention to details in naviga-
tion which can be obtained in the Royal
Navy with double and treble the amount
of men. Until, therefore, merchant
ships are manned equally with the Royal
Navy, it will be unjust to judge their
management from the same platform,
and it will be in vain to expect from
them the same attention to details.
With the limited crew of a merchant
sailing vessel, in disagreeable weather,
the heaving of the lead has always en-
tailed considerable extra work on the
watch at a time when men could be least
spared for the duty. In a screw steamer
the ship must be dead stopped to obtain
a reliable cast, and to insure that the
propeller does not cut the line. These,
with many other difficulties attending its
use, account for its frequent neglect.
With a more simple method of casting
the lead this neglect would vanish.
Sir William Thomson's patent deep-sea
lead can be kept, if required, constantly
going; and in those ships that have an
after wheel-house, and conveniently near
the taffrail, the machine can be worked
inside and made a permanent fixture.
This arrangement saves the attendance
of one man at night to hold a light, as
the wheel-house light can be hung in
front of the indicator. Here, therefore,
free from all weather, in a comfortable,
lighted-up room, without having to haul
in a wet and sometimes freezing line,
two men can, if necessary, cast the lead
every five minutes, with more satisfac-
tory results than could be obtained by
the ordinary lead and line without the
ship were dead stopped. It is not my
province to enter into the details of this
lead, and I think it will be more satis-
factory to the reader if I limit myself to
its results.
While the casting of the ordinary
deep-sea lead on a cold and dirty night
is a most troublesome ani disagreeable
duty, the casting of Sir William Thom-
son's lead by two men only is little more
to them than an amusement. Like every
other instrument it requires a little ac-
quaintance to manage it perfectly. To
obtain this I commenced my experiments
in the Atlantic, where there was no
chance of touching bottom. After at-
taching the tube that measures the depth
of the lead, the ship going twelve knots,
52
TAN NOSTRAND'S ENGINEERING MAGAZINE,
100 fathoms of wire were allowed to run
out; in four minutes the cast was com-
pleted, and the tube showed a perpen-
dicular depth attained of seventy-five
fathoms. This experiment was repeated
a number of times with about the same
results. The conclusion drawn from
them was that it was not prudent to al-
low the lead to descend with such
velocity, and in all future experiments
the amount of restraint put upon the
drum at the same speed of twelve knots
gave fifty fathoms for 100 fathoms of
wire run out. This, I considered, was
the safest speed to work the instrument,
and made any further use of the tube,
except in experimental cases, quite un-
necessary. Having worked out the
amount of restraint necessary, on the
revolutions of the drum, to give the per-
pendicular depth one-half of the wire
run out, with the ship running twelve
miles an hour, it was easy to write out a
rule for any other rate of speed of the
ship sufficiently accurate for all ordinary
purposes. With this rule I ran along
the north coast of Yucatan, over the
Campeche bank, for nearly two days,
the lead going every half hour, keeping
mainly, while along the coast in the
soundings, between five and ten fathoms,
without either the rule or the lead fail-
ing. Steaming, again, in the Mississippi,
to and from New Orleans, the experi-
ment was similarly repeated. Again,
rounding the Florida reefs and coast, the
same experiment was continued. Again,
crossing the banks of Newfoundland, it
was renewed; and, at last, from the
Fastnet to the bar of the Mersey. I
have therefore given this lead a thorough
testing.
Here at least science has answered the
aspirations of the navigator and supplied
him with an instrument with which in
her absence in thick weather he can
check the deductions of dead reckoning,
feel his way approaching any coast, sail
along it without losing his track, round
certainly and with confidence unseen
points of land, and all without inconven-
ience to any one. With such a lead on
board the neglect to heave it would in-
deed indicate some degree of foolishness,
but the neglect to use the lead ordinarily
in use proves only too much considera-
tion for the crew's opinion on such mat-
ters, and a consequent dislike to tease
and annoy them by forcing them to per-
form repeatedly what on a hard cold
night is to them an exceedingly un-
pleasant duty.
GEOGRAPHICAL SURVEYING.
By FRANX DE YEAUX CARPENTER, C.E., Geographer to the Geological Commission of Brazil.
Contributed to Van Nostrand's Magazine.
I.
In this paper I shall present a scheme
for the organization, the gradual develop-
ment, and the prosecution of a geographi-
cal survey in connection with the
Geological Commission,* which, in .the
efficiency of its results, will satisfy not
only the present demands but also the
future needs of the Empire of Brazil for
very many years to come. In the rapidi-
ty of its progress, this survey will be
* Charles Frederic Hartt, Professor of Geology in the
Cornell University, and Chief of the Geological Com-
mission of Brazil, died on the eighteenth of March last,
in Rio de Janeiro, where he was engaged in preparing
the reports of his Survey.
His death, and the dissolution of the Commission, of
which he was the founder and director, have prevented
the realization in Brazil of the plan of Surveying pro-
posed in the accompanying pages.
especially adapted to a country of so
vast an area and comparatively sparse
population, and as an adjunct to the
above Commission, and in great part
carried on by the members of the same,
without interfering with the ends of
that body, it can be maintained at an
expense so moderate as to be in con-
formity with the present desire for econ-
omy and retrenchment in the public
service.
THE PROPOSED PLAN OF SURVEY.
The immense empire of Brazil is yet
without reliable geographical- maps.
These are necessary to the national wel-
fare. The question arises as to what
GEOGRAPHICAL SURVEYING.
53
kind of maps will be sufficient to satisfy
the imperative needs of the country and
of science. The plan of survey which I
shall advocate is a mean between that
system which takes cognizance of every
house in a village and every little undula-
tion in the landscape, and that want of
system in which are represented whole
mountain-chains that do not exist, or
actual topographical features are delin-
eated with gross inattention to accuracy.
It is a judicious mean between the slow
and laborious processes used, for in-
stance, in the Ordnance Survey of Great
Britain, and the sketchy and unreliable
information gained by the early ex-
plorers of the New World, from whose
results our first maps were compiled.
These last are scarcely more graphic and
complete than our present maps of the
moon, and in fact, speaking broadly,
they are not so accurate as the latter,
which are, in great part, photographs of
the surface which they represent. With
these mere hints of the geography of its
country a people should not feel obliged
to rest satisfied until it can sustain a
minutely topographical survey.
AN EVOLUTION IN CARTOGRAPHY.
The demand for maps depends upon
the population and civilization of a
country. In the beginning a rough
sketch will answer the purposes of the
pioneer. As the region becomes inhab-
ited better maps are wanted* and finally
the people require the nearest possible
approach to absolute accuracy in the de-
lineation of topographical features. Map-
making in every country must follow a
regular evolution from the incomplete to
the complete.
Reviewing the origin and growth of
the cartography of a country, we see how
faulty it is liable to be. The first ex-
plorer is the first contributor to the
geography of a region. By way of il-
lustration, let us follow one of these
pioneers as he traverses Brazil from
South to North. Following up a branch
of the River Plate, he records the ap-
proximate directions and distances of his
journey, which he obtains, perhaps by
the use of unreliable pocket instruments,
perhaps by an occasional glance at the
sun and his watch, or, more probably,
by estimating at night the latitude and
departure which he has made during the
day. At a certain period of his march
he finds a river entering from an easterly
direction, whose volume he measures
with a glance of the eye. Farther on,
he encounters a tribe of Indians, whose
village is situated upon the west bank of
the river; he counts their houses, and
makes the number of these a key to the
extent of the population. At the fol-
lowing night he camps at the foot of a
cataract. Impressed by its grandeur, and
also by a kind of optimism, common to
early explorers, and which will not allow
him to underrate any of the glories
which he sees, he estimates its height to
be at least twenty meters, when in reality
it is but ten.
At a certain point whose latitude and
longitude he determines in a rude and
hasty way with the sextant which he
carries, he leaves the main stream and
follows a tributary to its head in the
highlands, where he crosses the divide be-
tween the great Parana — Paraguay basin
and that of the Amazon. ITpon the
summit of the plateau he tests his alti-
tude above the sea by noticing the tem-
perature of boiling water, or by reading
the indication of his single aneroid, un-
reliable methods which have been known
to give results even a thousand meters
wide of the truth.* Continuing down
the Araguay, he observes the trend of the
mountain-range along his route, and de-
scending the Tocantins, he makes a simi-
lar survey extending to Para.
We do not disparage the work of this
man. Under the circumstances of hard-
ship and peril by which he is surrounded
he does all that is possible, and his re-
port is really of great value until some
more reliable exploration can be made;
still, for all of that, it is none the less in-
correct and incomplete.
It is from such sources as this that the
material for our first maps is drawn. In
* Gibbon's observations at the head of the Amazon,
both the mercurial and thermo-barometer being used,
show a discrepancy between the two which is equivalent
to 300 meters of altitude. The height of Mount Hood, in
Oregon, as given by one authority, who determined it by
the boiling point of water, is almost 2,000 meters greater
than that indicated by the cistern barometer and by tri-
angulation. In the writer's own experience he has en-
countered an aneroid record, upon one of the peaks of
the Sierra Nevada Mountains of the United States, which
made the height of this mountain to be 3,000 feet above
its true altitude. It is a noteworthy fact that these pre-
liminary determinations, made with the above faulty
methods, resemble the estimates of the early explorers,
inasmuch as they almost invariably give exaggerated alti-
tudes ; perhaps the opinions and imagination of the ob-
server are allowed to form, in some unaccountable way,
a factor in these results.
54
VAN nosteand's engineeeing magazine.
later revisions there may be introduced
the results of desultory explorations of
mines, railway routes and navigable
waters, as well as the meagre topograph-
ical data acquired by the land surveyor
in running boundary lines of private
estates, but still, taken at its best, a map
constructed in this way falls far short of
its purpose as a picture of the confirma-
tion of the earth's surface, or as a guide to
the traveler, the geologist, or tx> the capi-
talist who wishes to invest his money in
the development and internal improve-
ment of his country.
FAULTS IN EXISTING MAPS.
In his compilation of the scattered in-
formation at his disposal the cartog-
rapher finds that a certain district of
country has never been entered by the
engineer. He knows, however, that two
rivers rise somewhere in this terra in-
cognita, and he feels it safe to predicate
a divide between them. He also, thinks
it safe to presume that this divide is a
range of mountains, of greater or less
height, and, in his desire to give an ap-
pearance of finish to his chart, he does
not scruple to insert at this place an
ideal mountain system, and represent
it as drained by the upper tributaries of
the two rivers, concerning whose head-
waters in reality nothing is known.
These physical features soon come to be
reproduced, with more or less variation,
in other maps, and in this manner errors
are grounded in the national geography,
from which they can only be eliminated
by a systematic geographical survey.
Like national myths they stubbornly
refuse to give way until eradicated by
true scientific research.
Supposing, on the other hand, that
the compiler, accepting the report of the
explorer, who claims to have discovered
a range of mountains between the Rio
Parana and the Rio Araguaya, wishes to
represent them upon the map. He has
no mathematical data to insure their
position, and no sketches or other in-
formation from which to draw their in-
tricate topographical features, and so he
evolves from his imagination an utterly
impossible chain of mountains, out of
place, artificial, conventional, and even
mechanical in their regularity. These
he depicts in that stereotyped form of
delineation, which is known in the
modern geographical draughting-room
as the " caterpillar " formation.
THE RELATIONS OF GEOGRAPHY TO GEO-
LOGY.
Upon such an unfaithful map as this
it is impossible to faithfully represent
the geology of a country. If the geolo-
gist attempts to lay down his conclusions
upon a sheet of this kind, its errors will
continually clash with his truths. The
configuration of the land, as it appears
upon this erroneous drawing, might in-
dicate that it belonged to a certain geo-
logical age, and that, in fact, it could
not be referred to any other; the geolo-
gist, visiting and studying the country
itself, finds that it is of a later and
entirely different period. But if he
paints it as it really is he publishes a
glaring anachronism to the world, for
the color which represents the rock of
one geological epoch overlies, upon the
map, the physical features which are
peculiar to another age. As in the
artistic and true delineation of the
human figure every feature must be the
exponent of anatomical structure, so in
topography, every representation of
topography must be true to geological
structure. Ranges of mountains, mean
disturbance or great erosion of certain
strata, and each has its own characteris-
tic features as sharply defined as those
of an animal. This should be thoroughly
understood, and those immense lines of
sierras which are supposed to separate
certain river basins, or are delineated in
the very heart of regions of which we
have no knowledge whatever, should be
erased from the national maps until
these districts can be explored. In the
course of his travels the geologist may
find some physical feature of great im-
portance, which he wishes to portray,
in area and position, upon his chart, but
the best maps at his disposal represent a
topography utterly at variance with
geological structure, perhaps a sharp
ridge of mountains where there should
be a plain, and so they are of no use to
him. Or he may find himself obliged to
color the top of a mountain peak with
the tint conventional to the bed of a
lake, and in this manner science is made
ridiculous.
To take an illustration nearer home,
suppose that the group of mountains that
GEOGRAPHICAL SURVEYING.
m
abut into the sea in the vicinity of Rio
de Janeiro have intervening valleys filled
with alluvium, which is really the truth.
Suppose that the limits of these mount-
ains have never been accurately determ-
ined, which is also true. In this case, it
is easy to be seen that if the geologist
lays down upon the map the alluvial
deposits in their true extent, they will
here and there encroach upon and over-
lap the rugged masses of gneiss, and in
places will extend far up the steep preci-
pices of the mountain side. To avoid
this absurdity the geologist is forced to
be as inaccurate as those who have gone
before him, and, in general, every error
in the geographical map mast be con-
tinued and apparently sanctioned in the
geological chart that is based thereon.
It becomes therefore absolutely neces-
sary that the work of the geologist
should be preceded by and based upon
that of the geographer, and that he
should work in conjunction with the lat-
ter. In the exploration of a new coun-
try the geological party should make its
own topography ; and in the United
States of North America, where the ex-
periment has been most efficiently tried,
this is always the case.
A good geographical map would give,
with sufficient completeness, all the lead-
ing topographical features of the region
explored, delineating with especial care
those peculiarities of structure which are
the keys to the different formations. It
would display the shape and position of
bodies of water, and show how the di-
rection of a stream is changed and de-
termined by the accidents of a broken
and displaced stratification, and by other
•circumstances of its boundaries. If re-
strained by canon walls its route would
be angular; down a steep gradient it
would be direct; and in the level allu-
vium near the sea its track would be
tortuous and broken into bayous. This
map would distinguish between the
rounded slopes of a synclinal valley and
the abrupt sides and angular cross sec-
tion of an anticlinal cleft; and between
the sharp edges of the volcanic rock and
the eroded angles of the sand-stone. If
there was exposed a great "fault " in the
stratification, it would show it at a
glance, with its precipitous bluff of ex-
posed strata on one side, and, on the
other, its gentle declivity of tilted sur-
face rock. And, drawn in contour lines,
it would reveal, not only the heights of
peaks and passes and other vertical dis-
tances from plane to plane, but also the
various orographic forms, each of which
is full of meaning to the geologist.
ECONOMICAL USES OF THE PROPOSED
MAPS.
Aside from being quite indispensable
to a scientific commission, in the various
ways that have been mentioned, these
maps can be made a graphic supplement
to their report in numerous other par-
ticulars, and can be made to embody the
stores of practical information which
they gather incidentally to their regular
work. Upon it they can display the
valleys of arable land and the plains
adapted to grazing. The forests of tim-
ber can be laid down, and, from this
drawing, their areas and values can be
closely estimated. Advantageous sites
for colonies can be noted here. The
superficial contents of coal-beds and ore-
deposits are given, and not only does a
geological chart reveal where the
precious and useful minerals are, or may
be found, but it also furnishes that nega-
tive information, equally valuable to the
miner, which defines to him the larger
districts in which it is impossible for
them to exist, and in which, consequent-
ly, it is a waste of effort to search for
them; it is here that the science of
palaeontology is especially useful. If
any portion of the country lies at a great
elevation, the altitude limits of the vari-
ous forms of vegetable growth may be
traced, and also the limits of the possible
culture of grain, coffee, cotton, and the
other principal products. In this man-
ner the map is made a general statistical
report upon the value of the national
domain.
The economical ends served by a work
of this nature in the development and
settlement of a new country, cannot be
too highly esteemed. Every stream of
importance is surveyed, in all — except
those minor branches whose courses can
be traced in from the adjacent mountain
stations — the frequent tests for altitude
along its banks determining the rapidity
of its descent. The amount of water-
power which it represents, and its value
as a motor for machinery, and as an
agent in hydraulic mining and diamond-
56
VAN NOSTRAND's ENGINEERING MAGAZINE.
washing. This profile of the bottom of '■
the valley also decides the feasibility of
railways or other lines of communication \
by this route, while the sketches of the
adjacent hills show what room there is
for such a road, and, in connection with
this, the geologist's report will give a j
general idea of the rock or other ma-
terial with which the engineer will have
to contend and work. In the survey of
a range of mountains careful readings
for altitude are made, not only on the j
summits of the peaks, but also at the j
passes, or low depressions in the divide,
while the slope of the descent from the
summit to the valley will be delineated
in contour lines drawn at such vertical
distances as circumstances may require.
It must be admitted that these contours
will only approximate to their true '
places, yet their number will be correct,
and their positions will be such that they
will give with sufficient certainty the j
various gradients that occur in the as- j
cent, so that, by counting the meters of
rise for every kilometer of horizontal ad-
vance, as shown by the scale of the map, >
the engineer or capitalist, in his distant
office, with this sheet before him, can
form a very satisfactory idea of the
practicability of a proposed railway, and
can select the most advantageous route ;
for the preliminary survey.
The meteorological data accumulated '
in the process of this work are valuable,
not only in the determination of the ver- !
tical elements of the survey, but also as |
an illustration of the general laws of i
drought and excessive rainfall. At in- j
tervals throughout the country, the de-
clination of the compass needle will be !
observed, and will be published for the ]
guidance of land surveyors who may not |
be proficient in astronomical observation.
The positions and supra-marine eleva-
tions of all villages, important fazendas,
medicinal and thermal springs, ancient
ruins or other discoveries in archaeology, !
supplies of water in a dry country, or of
pasture in a barren district, and all other
places of interest to the traveler, will
be determined. The roads and trails
already in existence will be surveyed i
and mapped, while a leading object of j
this enterprise will be to find shorter and ,
easier lines of travel. The explorer who
opens a new pass through the mountains
is a far greater benefactor to mankind |
than he who discovers and names a con-
spicuous peak.
Many of the national surveys of
Europe were founded on military
necessity, tfaat is, the necessity of having
correct information to govern the move-
ments of armies in time of war and the
incessant transfer of troops in time of
peace. In some of these countries their
early maps were withheld from the
citizen, whose taxes had paid for their
construction, and to as recent a date as
1857, in one or two cases, they were
kept secret for use in some contingent
war. This argument of military necessi-
ty will have but little weight in Brazil,
whose rulers, knowing that a country
strong in peace will also be strong in
war, take the enlightened and advanced
policy of encouraging the peaceful pur-
suits of life, as the surest basis of nation-
al strength. Still it must be acknowl-
edged that these maps would be of
excellent service in the administration
of the affairs of distant provinces, in the
transportation of military supplies, and
in the garrisoning of frontier posts,
although the country is to be congratu-
lated that, for every soldier to whom
they would be useful, a hundred immi-
grants would be benefited by them.
THE INTENTS OF THIS ESSAY.
While entertaining no wish to make
this article popular, in the ordinary sense
of the word, I shall seek to exclude from
it all formulas, equations for computa-
tion, and other material, purely mathe-
matical, upon which the surveyor bases
his work, and as far as possible I shall
avoid those technical terms which would
be embarrassing to the reader who is not
an engineer. The fundamental princi-
ples of geographical engineering are the
same all the world over, and in every
mathematical library there are books of
reference which give all the laws and
formulas necessary for a work of this
kind. Therefore, nothing would be
gained by their repetition here. Spe-
cialists in geodesy, astronomy, and
hypsometry have investigated their vari-
ous branches, have published their re-
sults, and these, in their purity, are
applicable to any quarter of the globe.
One, for instance, has applied the theory
of least squares to geodetic computa-
tion; another has invented the zenith
GEOGEAPHICAL SUKVEYING.
57
telescope for latitude observations; and
a third has traced the horary curve in
the barometric record. All of these dis-
coveries fall within the comprehensive
department of the geographer, who
supplements these studies by utilizing
their results in his labors in the field
and office; or, if he is about to write a
brief exposition of the subject of geo-
graphical surveying, it is his business to
describe, in a straightforward manner,
the way in which practical application
of these truths is made.
This paper will be, in general, a
description of the most approved meth-
ods, the economical devices, and the
practical results of a successful geo-
graphical survey, working in obedience
to the directions of the chief of the
commission to which it is attached, and
covering such areas as may be designated
by him as most worthy of geological
and geographical delineation. From
time to time, as occasion may offer, and
especially at the conclusion, the project
will be adapted to the Empire of Brazil,
as it is quite impossible to propose a
plan of survey which will be applicable
to all countries. Although, as has been
stated heretofore, the general principles
underlying this kind of work are the
same wherever physical laws prevail,
and the face of the country is wrinkled
with mountains and valleys and furrowed
with the river-bed and canon, yet there
are physical conditions peculiar to every
land, as well as circumstances of area,
population, and wealth, which require
that it should have its own type of geo-
graphical survey, and not copy too ex-
actly those of any other nation.
THE BEST TYPE OF SURVEY FOR BRAZIL.
Considering the circumstances of area,
population and wealth, it is evident that
the national surveys of Brazil should be
" geographical," in a very liberal sense of
the word; that is, that they should be
comprehensive in their scope, rapid in
their execution, and sufficiently accurate
without being too punctilious and too
excessively minute. It is only within
the present generation of engineers, and
particularly in the western hemisphere,
that there has grown up an important
distinction between topographical and
geographical surveying, and even now it
is hard to define the limit between them.
The latter is an outgrowth and extension
of the former and an adaptation of it to
the mapping of large domains at the
least possible expenditure of money and
time.
DISTINCTION BETWEEN THE GEOGRAPHER
AND TOPOGRAPHER.
As one of the many points of differ-
ence between the geographer and the
ordinary topographer, we may mention
that the former, in his travels and sur-
veys, accommodates himself to the roads,
trails, or other open and easy routes that
already exist, and it is but seldom that
he finds himself obliged to make a path
for his survey to follow. In the ascent
of some mountains it may be necessary
to cut a road, and in the measurement of
the base line for his triangulation he may
have to prepare the ground before him,
but these are almost the only instances.
The topographer, however, in tracing a
contour line around the side of a mount-
ain, or in making parallel profile sec-
tions of the land, is not allowed to devi-
ate therefrom, and if the way is not
clear, he must wait, perhaps at great loss
of time, until his assistants have removed
the brushwood, or whatever other obsta-
cles may intervene ; in this respect he
resembles the railway engineer. Again,
in the selection of the stations for his
triangulation, the geographer makes the
best possible use of the mountains
of a country as he finds them, generally
accepting them as they occur; though
their arrangement, it may be confessed
here, is not always in such well-condi-
tioned triangles as he would desire. The
topographer, on the contrary, delays his
work by the establishment of arbitrary
stations where natural points are lacking,
and by the erection of artificial signals
on those mountain tops which the former
observes without such aid.
In the end it will be found that the
topographer's notes are so numerous and
in such detail that it may require several
centimetres of map to represent one kilo-
metre of the earth's surface; while to
the geographer, who is satisfied with the
general shape of a mountain-spur, the
approximate width of a valley, and the
more important bends of a stream, a
scale of one centimetre to several kilo-
metres may be sufficiently large for the
portrayal of the earth as he finds it. But
VAN NOSTRAND'S ENGINEERING MAGAZINE.
it will also be observed, by an economi-
cal government, that while the typo-
grapher consumes several years in the
survey of a thousand square kilometres,
the geographer will obtain a very satis-
factory knowledge of thousands of
kilometres in one year. And, in general,
the superior accuracy, or rather detail, of
the former, is purchased at an expendi-
ture of time and money so great that
only the older and wealthier nations
can afford the investment; while I hope
to demonstrate that the geographer's re-
sults are sufficiently complete for the
needs of Brazil.
THE GEOGRAPHER'S PROFESSION.
The geographer's work is a peculiar
and difficult one, and one for which his
ideas must become enlarged by a special
training. This is a branch of our pro-
fession for which no training-school pre-
pares its student and no text-book yet
published can instruct him. This is a
field in which the experienced topo-
graphical engineer, fresh from his labors
on park and landscape, or on the detailed
surveys of thickly populated Europe,
finds himself unhandy and incompetent,
for much of the experience and tradition
that he brings with him is an incubus
to retard him. To become efficient in
this new service he must forget much of
the rule and routine that he has learned,
and accustom himself to taking broad
and bird's-eye views of the country.
Strange as it may sound, he must
make it a matter of duty and pride to
overlook and neglect much that is near
at hand, and remember that, although a
mole-hill at a distance of a few feet sub-
tends a greater visual angle than a
mountain as many miles away, yet it is
the mountain, and not the mole hill, that
deserves delineation upon his map.
Hitherto he has been local and narrow in
his range; he must now become geodetic,
else he will accumulate a mass of minu-
tiae, whose representation would be in-
finitesimal on a map of the proposed
scale, and which is hence but an incum-
brance to his books, and even worse than
cumbersome, inasmuch as its presence
excludes other and more valuable data.
In short, the topographer considers the
earth minutely, and with a microcosmic
view, but the geographer is a man of no
such narrow horizon, and trains himself
to look upon it as a macrocosm, or great
world.
THE INSTRUMENTS USED.
Of scarcely secondary importance to
the men of a geographical corps, are the
instruments with which they shall work.
The tools which have been devised for the
ordinary surveys of land and landscape
must be left at home with the slow and
tedious method from which they cannot
be divorced. In a work of geographical
extent the spirit level, chain, and tally-
pins are out of place, and whosoever,
making accuracy his plea, attempts to in-
troduce them there, will find his own
ends defeated by them. Once upon a
time, for instance, an engineer was in-
trusted with the survey of a large tract
of new country. A certain sum of
money and a limited period of time were
given to him, a stated area of territory
was assigned to him, and in return the
authorities expe "ted of him the most ac-
curate and impartially complete map
that his means would allow.
The time and resources granted him
would permit him to touch the country
but lightly and by swift marches, but, as
this was intended to be only a reconnois-
sance, nothing more was expected of him
than to trace the conformation of the
land in a general way. He was an
honest and conscientious engineer, and
so great was his zeal for accuracy, or
nicety rather, that he was scrupulous to
a fault. He abused the maxim which
says that whatever is worth doing at all
is worth doing well. For determining
the altitude of stations along the route
he used the spirit-level, and their inter-
mediate distances were found by stadia
measurements, which system, though
considered incautiously rapid in topogra-
phy, is too laggardly slow for the or-
dinary purposes of geography. In this
manner he crossed his territory with a
few lines of march whose profiles were
as trustworthy as those of a railway sur-
vey, and far more accurate than the pub-
lic interest demanded, while between
them there were large areas untouched
and unseen, and of these the public,
whose agent he was, had commissioned
him to obtain information. The failing
of this engineer was a common one; he
neglected to distribute his resources
fairly and impartially, and while half of
GEOGRAPHICAL SURVEYING.
59
his map is reliable the other half is con-
jectural.
It would be too long a task to de-
scribe in detail all the instruments used
in geographical work, or to rehearse all
of the devices employed in its prosecu-
tion; however, the most necessary and
novel features will be noticed here. At
the basis of the work is the transit, or
theodolite, which, with compass-needle
attached, is the engineer's constant com-
panion, without which his occupation is
gone, no matter in what field his labor
may lie. As an appurtenance to this,
not the chain nor the stadia, but the
odometer wheel, has become the recog-
nized means of linear mensuration in the
survey of streams and the determination
of those distances of route and detour
which are so useful in filling in a trian-
gulation chart. Instead of the level, the
cistern barometer gives the heights of
mountains, mines, passes, camps, vil-
lages, and other important positions,
while the aneroid barometer, portable as
a watch, and as easily read, will tell the
altitude of minor points and give with
sufficient closeness the data from which
may be plotted the profile of the odome-
ter's itinerancy.
THE PERSONNEL OF A GEOGRAPHICAL
CORPS.
These are the three classes of instru-
ments that are indispensable; the purely
geographical party required to use them
need consist of but three men, the en-
gineer, the meteorologist, and the
odometer recorder. To this corps it
may be deemed advisable to add a fourth
member to act as an assistant to the en-
gineer, and, by personal obervation and
experience acquire that facility in the
practice of his profession which will fit
Lim, in the course of a brief period of
training, for the responsible position
above him. Such a person should al-
ready have the theoretical education of
an engineer, and some skill in drawing.
If it is not practicable to make this ad-
dition to the corps, it is well to choose
as an odometer recorder one who pos-
sesses the acquirements stated above,
and to consider that position, whose
appertaining duties are light, as prepar-
atory to the grade of engineer. As for
the meteorologist, his is an intricate
science which connot be studied too
thoroughly, and barometric hypsometry,
should be regarded as a profession quite
distinct from the engineer's, although
necessarily subordinate to it.
The various duties involved in the
measurement of the base-line, at the
opening of the season, may demand the
services of a larger body of men than
this, but, once in the field, any addition
to the above number, except as muleteers
and servants, will be superfluous, as far
as the geographical work is concerned.
One surveyor can see as far as two, and
one man is able to take note of all of the
country visible from his route of travel.
No axemen are needed, for if there is a
tree in the way, the line must yield to
the tree ; the resultant error will be trif-
ling and will not be apparent in a map
which represents several kilometres of
territory on one centimetre of space.
Neither is there any necessity for rod-
men, with rods of two targets for mi-
crometer measurements or one target for
levels, who would retard the corps by
the long delays consequent upon their
transfer from the stations in the rear to
those in advance. This party travels as
a unit, moving as fast as its animals can
walk, and is never broken, a considera-
tion which is of value in a country of
hostile people.
Of course the scope of the work may
require the service of a great number of
professional men, but its best progress
demands that they should be divided
into corps of the above size, which shall
work in concord and under one general
head. This director will assign to each
party its territory for the season, and
upon the borders of these areas, the va-
rious engineers will make rendezvous
from time to time, as circumstances may
admit, with their neighbors of the ad-
joining fields, for the purpose of
reorganization, exchange and issue of
material, and especially for the compari-
son of sketches and geodetic data, so as
to insure the proper union of their sev-
eral schemes of triangulation. In order
to make the different systems of trian-
gles interlock in one grand plan, the
observer will frequently be obliged to
read angles to stations which lie on an
adjacent district, and which will be oc-
cupied by his co-laborers for the purpose
of reciprocal observations. It is there-
fore necessary that they should meet in
60
VAN NOSTKAND7 S ENGINEERING MAGAZINE.
occasional conference for the mutual
identification of those stations.
THE STATIONS OF SURVEY.
Guided by these thoughts, let us sup-
pose that we have completed our organi-
zation for a season in the field, and that
we are now on the ground ready for
work, at the place selected as the initial
point of the survey. As with all surveys,
this one will be executed from stations,
meaning thereby any points at which a
tripod is planted and an instrument ad-
justed, angles are read and sketches may
be made. Of these we shall occupy
four orders, of which, in importance, and
consequently in accuracy, the astronomi-
cal is first. Then comes the geodetic, or
trangulation station; the topographical
station, so designated for the sake of con-
venience; and, finally, the odometric, or
route station. In addition to the ends
which they are especially intended to
serve, each of these will be a meteorologi-
cal station as well. These five classes,
with the incidental details pertinent to
them, will now be considered in the
order named.
THE ASTRONOMICAL STATION.
Since the positions determined by tri-
angulation, or other system of survey in
which terrestrial objects alone are con-
sidered, are only relative to each other
and to the first station occupied, it is
evident that a map may be completed,
which, in itself, will have all of the ex-
actness of perfect truth, but whose place
on a projected surface of the globe will
still be uncertain. A map of a conti-
nent may be made, and this may be of
great use in the guidance of travelers
across the continent, and for the local
information of its inhabitants, but still
it does not play its proper part in the
grand plan of this earth's geography, and
define the situation of this land relative
to the other continents of the earth,
until it is bound into place by the meri-
dians and parallels, which are the warp
and woof of the structure of geography.
Therefore, in order to adjust our map,
when made, into its true place, we must
have the absolute determination of one
or more of its positions.
Now there is but one way of finding
the absolute position of an object on the
earth, and that is by going beyond the
earth, consulting the stars, and ascer-
taining its place relative to them. Hav-
ing two triangulation stations thus
located, the whole chart becomes ad-
justed to its place. Or, having the lati-
tude and longitude of our initial point
and the astronomical azimuth of a side
of a triangle leading from this origin, the
former serves to pin the plot to the pro-
jected map, and the latter is instrument-
al in orienting it into the area to which
it belongs.
POSITION OF THE ASTRONOMICAL STATION.
For every base-line measured and
developed there should be an astronomi-
cal station occupied, and as a matter of
convenience and co-operation they should
be in the same vicinity, although it is
not necessary that the station should be
directly over either end of the base.
Indeed, owing to great exposure to
the wind, or to inconvenience of ap-
proach, it may not be found practicable
to locate the astronomical station at any
of the points of the triangulation system,
or, to secure proximity to the telegraph,
whose office may be hidden in the heart
of a town, or the bottom of a vaDey, it
may be so secluded as to be quite in-
visible from those points.
If so, it may be easily connected with
them by running a careful linear survey
from the astronomical station to the
nearest geodetic station. If, owing to
the disadvantageous nature of the
ground, or other obstacles in the way, it
may be impossible to measure the dis-
tance directly between these two points,
the engineer can connect them by a
broken line, reading at the astronomical
station the angle between the meridian
mark, already fixed by the astronomer,
and the direction of his first course, and
afterwards referring the direction of each
measured section of his traverse to that
immediately preceding. From these re-
sults he calculates, in meters, the differ-
ence of latitude and departure between
the two points, and then, transforming
the meters into seconds of arc, he com-
putes their difference of latitude and
longitude.
NUMBER OF ASTRONOMICAL STATIONS.
For a commission of moderate size, in-
cluding one, two, or three engineering
corps, the triangular development of one
base will cover as much territory as can
be surveyed by them in a single cam-
GEOGRAPHICAL SURVEYING.
61
paign, and therefore one astronomical
position a season is all that this survey
would require during the first year or
two of its organization. A series of ob-
servations extending through a couple of
weeks, in favorable weather, or through
a month at the farthest, will determine
the geographical co-ordinates of our
point of departure. These can be made
by the astronomer while the engineers
are measuring the base-line and develop-
ing the same, the director is perfecting
his arrangements, and "the purveyors are
preparing and distributing the supplies,
instruments, and all of those numerous
articles of equipment which are the fur-
niture of a scientific field season. At
the same time, the meteorologist, by a
set of hourly barometric and psychro-
metric readings accumulates data whose
digest will give the vertical co-ordinate
of this place with the possible error of a
very few feet, and this completes the de-
termination of its position with reference
to a system of co-ordinates whose origin
is at the level of the sea at the point
where the first meridian crosses the
equator.
For so short an annual term of service
it might not be advisable to keep an as-
tronomer constantly in commission, nor,
at present, might it be well to go to the
expense of the costly and elaborate in-
struments requisite for the best astro-
nomical observation, provided that the
co-operation of the Imperial Observatory
could be secured and an astronomer
could be detailed from there for that
purpose. In addition to the gratification
to be derived from the warranted excel-
lence of the results which would be fur-
nished by the skilled assistants of that
institution, this corporation would be a
matter of economy to the Government,
and also, what is especially to be desired
between any two scientific bodies, a
means of friendly relation and inter-
change of information which would cer-
tainly prove of mutual value.
ASTRONOMICAL METHODS.
For the determination of the latitude
of our point of outfit the zenith tele-
scope would be used; while the longitude
would be found by the telegraphic ex-
change of time signals, a method which
has lately been so successfully introduced
by the Astronomical Commission. The
present wide-spread extension of lines
of electric telegraph within the borders
of Brazil is especially favorable for a
survey of this nature, whose longitudes
would be based upon telegraphic commu-
nication with the national observatory.
The lines along the coast afford a gen-
eral connection with the northern and
southern provinces of the Empire, while,
by the numerous branches which accom-
pany the railways into the interior, points
which lie far to the inland could be re-
ferred to the meridian of Rio de Janeiro,
which, in its turn, has communication
by cable with the observatories of Eu-
rope.
Thus it will be seen that the engineer
need not be confined to any unfavorable
locality in the selection of the ground
for his base line, nor need the chief of
the commission be restricted in his choice
of areas to be surveyed. From the
railways either constructed or contem-
plated it would probably be possible to
reach any of the settled portions of
Brazil without seriously overtasking the
accuracy of the triangulation, and, if it
were required to carry the survey still
farther, longitudes determined by the
method of moon-culminations would be
sufficiently exact for the less important
regions beyond.
ORIGIN OF THE TRIANGULATION.
An inland survey, based upon trigono-
metrical methods, progresses most suc-
cessfully from an initial source concen-
trically outwards. The most fortunate
location for the initial line is in the cen-
ter of some broad valley or intermontane
plateau, whose level expanse offers fair
ground for the measurement of the base,
and whose open field is favorable for the
gradual and symmetrical development
of the same until it shall reach the lines
of the remotest triangles, in which it be-
comes a metrical standard for finding
their length. In an extensive survey,
lasting for years and covering broad ter-
ritory, a series of bases are indispensa-
ble. These act as cheeks upon each
other, and the net-works of triangles
emanating therefrom are dovetailed into
each other, and, in their adjustment to
fit, each to each, what little error they
may have accumulated is reduced to a
minimum.
For instance, on each side of a range
62
VAN NOSTRAND'S ENGINEERING MAGAZINE.
of mountains there is an open basin. In
each of these an astronomical station is
established and a base is measured. On
the comb of the intervening sierra, one-
hundred miles apart, stand two pre-emi-
nent mountain peaks. The latitude and
longitude of each of these, with the
distance between them, is determined
from the two origins independently.
They check each other, verifying, in
their agreement, the accuracy of both
systems, or showing by their disagree-
ment that there is an error somewhere,
and the long line, drawn by the labor-
saving appliances of trigonometry,
through a hundred kilometres of aerial
route, a thousand meters above the val-
leys and chasms which it spans, is now
ready to be used as a new base in the
primary triangulation.
It may be difficult to find a favorable
locality for the source of a triangulation
immediately upon the sea-shore, as there,
unless there are islands in the adjacent
ocean, one side of the field is quite open
and affords no stations to be occupied.
If it were not for this objection it would
seem best to measure a succession of
bases along the coast of Brazil, and
thence develop them westward. A tri-
angulation is always most accurate in
the vicinity of its origin, and as it be-
comes more and more remote from its
initial ground it becomes less reliable,
owing not only to the continued multi-
plication of the original error of the
base, but also to the accumulation of in-
accuracy, and mistake* from other
sources. Now, the population of Brazil
is thickest along the sea, and thence, into
the interior, at least in many provinces,
it gradually thins out. The importance
of the country and the necessity of
having truthful maps correspond to the
density of the population. Add to this
the fact that the most interesting geology
of Brazil is on the sea-board, and,
furthermore, the important considera-
tion that the coast of a country, for pur-
poses of navigation, demands a more
rigorous geographical determination than
the interior, and it will be seen that the
triangulation upon which this delineation
* There is an important difference in the meanings of
the terms "mistake" and "inaccuracy." If a man,
carelessly reading a vernier whose indication is 38' 45",
calls it 39' 45", he is guilty of a mistake. If from parallax
or some defect in vision or judgment, he calls it 36' 40",
he is inaccurate. Mistakes are due to want of care ; in-
accuracy, to want of precision.
depends should not originate too far
away. In a general survey of Brazil,
therefore, the first series of astronomical
stations and bases should be established,
if not upon the sea-shore itself, at least
upon the first plateaus that are encount-
ered between the mountains of the in-
land.
POSITON OF THE BASE-LINE.
In its direction and position the base-
line should bear judicious relations with
certain hills, knolls, corners of terraces,,
or other prominent elevations in the vi-
cinity, which may be selected as sites
for the stations to be occupied in its de-
velopment. The plans for its expansion,,
matured before its position is selected,
should include two prominent peaks in
the horizon, remote from the origin and
from each other, whose distance apart
this measured length will be instrumental
in determining. The ground upon which
it is to be measured, should be as smooth
and bare as possible. It should be free
from brush, tall grass, or other vegeta-
tion, and also from hillocks and gulches,
which are serious impediments to a work
of delicate mensuration. Whether it is.
level or not, provided its slope be grad-
ual and even, is of secondary importance,
as corrections may be easily applied to
cancel the effect of its gradients.
LENGTH OF THE BASE.
The length of the base may vary from,
two to ten kilometres. In the opinion,
of many engineers more than four kilo-
metres of measured length is zeal gone
astray, for the advantages of accuracy
gained by such excess would be obtained
more easily by devoting the extra time
to a more elaborate trigonometrical de-
velopment. No arbitrary rule can be
applied here, however. All must depend
upon the judgment of the engineer, who
will consider his surroundings, and if
they are favorable for a slow and pro-
gressive development, a short base will
answer, but if he is obliged to carry his
triangulation from the base stations to
the distant mountains by an abrupt
transition, a longer one will be required,
to prevent too great acuteness in those
remote angles.
INSTRUMENT OF MEASUREMENT.
Since rapidity, as well as accuracy, is
an object, we use a steel tape, ten or fif-
GEOGRAPHICAL SURVEYING.
63
teen metres in length, as a measuring
unit. In the swivel at one end of this
there is a thermometer which tells the
heat to which the tape is subjected at
any time; there is also a micrometer
screw, by which it can be lengthened or
shortened in compensation for any possi-
ble change of temperature; and there is
a dynamometer attached to govern the
tension applied, which should amount to
three or four kilograms, being at every
application the same as it was in the orig-
inal test for length, to which the tape
was subjected.
Thus, as this apparatus is applied, in
the process of measurement, it is under
a constant strain, which preserves it
from the error from sagging, to which
all flexible cords are liable, and its length
is always corrected to meet the contrac-
tion and expansion which the metal is
constantly undergoing as the tempera-
ture varies. Should this micrometer be
but incompletely graduated, so, for in-
stance, as to be adjustable only for every
five or ten degrees of thermometric
change, or should it even be wanting
entirely, very good results can still be
obtained with the steel tape by reading
the thermometer at every application,
and, in the final computations for length,
making the necessary temperature cor-
rections. Used carefully and with intel-
ligence, this instrument is one of the
most valuable adjuncts of the geograph-
ical survey, and, in the hands of consci-
entious and interested observers, it is
capable of results that are very near the
exact truth; the error ought not to ex-
ceed one centimeter for every kilometer
of measured distance.
METHOD OF MEASUREMENT.
The mensuration may be made on
wooden plugs, with smooth, flat upper
surfaces. These are driven firmly into
the ground along the alignment at inter-
vals equal to the length of the tape, and
should be allowed to project above the
earth sufficiently to permit this cord to
swing clear of all inequalities in the
surface, or other obstacles between the
two stations. Or, instead of these, little
stools of plank may be used; these
should have short, pointed iron legs, to
be forced into the ground, so as to hold
the wooden block firmly in position.
When all things are ready a distance
of one or two kilometers can be meas-
ured in one day. But, on account of any
possible inefficiency in the compensation
for temperature, and also because even
the best assistants are liable to a per-
sonal equation in sticking the marking
pin, some invariably inserting it to the
right of perpendicular, and others the
reverse, it is well that it should be
measured several times, and by different
persons, and a mean of the results taken.
Then it should be leveled, in order that
each tape-length may be corrected for
its gradient, which is done by a simple
trigonometric process, and finally it is
reduced to its corresponding concentric
arc at the level of the sea, when it is
ready for use in the system of triangu-
lation.
THE ASTRONOMICAL BASE.
The method of base-measurement by
astronomical observation is sometimes
resorted to in geographical surveying,
but this process will be noticed here
only sufficiently to point out the serious
objections that there are to its use.
Having the latitudes of the two ends of
the base and the azimuth of one from
the other, it is a simple matter to com-
pute their distance apart. This seems to
afford an economy of labor over the
former method that involves the determ-
ination of the latitude and longitude of
the first station, the azimuth of the base-
line, and its length by direct measure-
ment; this one requires the determina-
tion of the latitude and longitude of the
first station, the azimuth of the base-
line, and the latitude of the second
station. The latter is apparently the
simpler and shorter task, and since both
methods are based upon astronomical
observation they would appear to be
equally reliable. But they are not.
Experience has long since taught the
scientific world that the probable error
of any ordinary astronomical result is
several meters at the very least, and that
it is not safe to put absolute reliance in
those reports which give a latitude down
to a very small fraction of a second.
Now, in that system of triangulation
whose position is based upon the astro-
nomical determination of one point only,
an error of a few meters in the latitude
of that point will not do material injury.
It will simply displace the entire trian-
64
VAN nostrand's engineering magazine.
gulation scheme, as a whole, so much to
the north or the south, while, since the
length of the base, or measuring unit of
the proportions of this scheme, was
accurately found, there will be no error
in these proportions. But, in the astro-
nomical measurement of a base, suppose
its two terminal points to be in their
most favorable position, that is, on the
same meridian. The latitude determina-
tion of the southern station places it
several meters too far to the south of
its true position; that of the other, per-
haps, makes it an equal distance too far
to the north. Hence it follows that
there is an error in the length of the
base equal to the sum of the two astro-
nomical errors, and this, in the develop-
ment, is multiplied almost indefinitely,
being repeated in any side of triangle as
often as the length of the base is con-
tained in the length of that line. This
is supposing the base to be an arc of
meridian; the greater its divergence
from the meridian, the more seriously,
for obvious reasons, will an error in the
astronomical determination affect the
length of the base. An astronomical
base-line, therefore, should only be used
when there are difficulties which make a
direct measurement impossible.
THE DEVELOPMENT OF THE BASE.
In the early stages of the develop-
ment, occuring, perhaps, on the level
surface of the plain, it will be found
necessary to use artificial signals. Great
tripods of frame-work, ten or fifteen
meters high, are constructed, leaving
ample space within for the observer and
his instrument. In erecting these, care
must be taken that none of the legs of
the tripod interfere with the view to-
wards any of the proposed triangulation
stations. Each of the signals terminates
at the summit with a flag-staff, to which
voluminous folds of white muslin are
nailed, while the body of the steeple is
wrapped with the same material and
decked with loose tatters and streamers,
which, by their ceaseless flutter in the
wind, offer occasionally a surface from
which the light is reflected to the eye of
the distant observer. The same purpose
may sometimes be better served by the
use of glittering sheets of tin, or by a
cone of the same material. These meth-
ods all have one very great advantage
over the more accurate heliotrope, that
is, they are always in position, and ready
for observations to be directed upon
them at any time. The use of the re-
flecting mirror, however, unless there are
a number of heliotropes in the field, in-
volves the loss of much time, as the in-
strument is transferred from one to an-
other of the neighboring stations.
The development stations should be
erected in conspicuous places, on high
ground or the salient angles of bluffs,
that the observer may know where to
direct his instrument in searching for
them, as it is extremely difficult to pick
out the faint glint of a few yards of
muslin on the broad light surface of a re-
mote plain. As the development con-
tinues and climbs from the foot-hills into
the high and peaked mountains, these
natural points are sharp and distinct
enough, being pnyjected against the sky
beyond, and the labor of station-building
ceases, except in cases that are very un-
favorable.
True, this triangulation by natural
points is not so precise as it is in some
geodetic surveys, and especially in the
surveys of coasts, where even the phase
of the conical signal is considered too
important an element of error to be neg-
lected; nor is it wise that it should be so,
for a fault of a few meters in the posi-
tion of a mountain-top in the remote in-
terior of Brazil, located by this plan, is
at present of no practical consequence,
and the nation cannot afford to purchase
an accuracy imperceptibly greater than
this by an expenditure that would many
times exceed the cost of this method of
survey. Considering a mountain as a
land-mark by which travelers are assured
of their place and are guided as they go,
it will be seen that, to men who travel
by land, a small fraction of a kilometer,
in latitude and longitude, is a deviation
which they cannot notice; to the voya-
ger at sea, however, the exact site of the
sunken rock which he shuns should be
known to him, in order that he may cer-
tainly avoid it. This is why the coast
survey, in most countries, precedes that
of the inland in the degree of accuracy
which characterizes it, as well as in the
amount of expense which attends it.
TfilANGULATION BY NATURAL POINTS.
It must not be inferred, however, that
GEOGRAPHICAL SURVEYING.
65
the use of natural points in triangulation
necessarily involves a serious accumula-
tion of error. In general, the engineer,
looking from one station to the next, can
readily cover, with the thickness of the
spider-line of his instrument, the highest
ground of the distant mountain, and
that point is selected as a correlative
station, because that is the spot which
can be most easily identified, either from
a distance, or upon the ground itself.
If this place is uncertain, as where there
are a number of pinnacles of equal alti-
tude, or not sufficiently prominent, as in
a plateau summit, some peculiar object,
as a solitary tree, or an isolated boulder,
should be chosen as a center upon which
to sight. If the profile of the mountain
has but little curvature, its culminating
point is usually determined by a pile of
rock, a clump of vegetation, or other
body upon its crest, which, although it
may not be distinctly visible from a dis-
tance, yet has the effect of increasing
the apparent altitude at that precise
locality. In the same way the useful-
ness of a monument of Tock, which a
party should always leave behind it
upon a mountain, as a signal to look
back upon, does not terminate at that
distance at which it becomes apparently
invisible. The eye will still be im-
pressed with the superior elevation of
the place where it stands.
If the round top of a mountain is per-
fectly bare, and offers none of these ac-
cidental aids to the observer, it is well
for him, in reading his first angle to it, to
keep the horizontal cross-wire tangent to
the surface, while he makes a careful
and deliberate search for its highest
point. Having decided upon this, he
brings the vertical wire upon it, and then
follows down the thread with his eye
until he finds it bisecting some well-
defined body in the field before him,
such as a corner of rock or the trunk of
a tree, and, in his repetitions of the
angle he fixes the vertical wire always
upon this object, while keeping the hori-
zontal thread tangent to the surface. In
this manner he secures to each of the
following readings the advantages of the
prolonged study given to the first, and
not only are his results more accurate,
as a whole, but they also agree better
among themselves, which is always a
source of gratification to the engineer.
Vol. XIX.— No. 1—5
THE MOUNTAINS OF BRAZIL.
In those lands which are remote from
the equator the summits of the high
mountains, of an altitude of three thou-
I sand metres or more, are above all vege-
j tation and in the belt of perpetual snow,
! and their occupation is a work of great
! privation and exposure. The mountains
: of Brazil are exempt from that disad-
! vantage to triangulation, as the climate
I is never rigorously cold here, and the
: elevation of the highest land is less than
J three thousand metres. The only ob-
1 stacles to be feared here are the oppo-
site disadvantages of too much vegeta-
tion, either hiding the tops of the peaks,
i or embarrassing the ascent to them, and
; too little height, whose result is liable to
be a system of round, well-preserved,
and insufficiently pointed mountains.
: But if those in the vicinity of Rio de
Janeiro are to be accepted as a criterion,
nothing more could be desired in the
way
of natural aids to triangulation.
PROGRESS OF THE TRIANGULATION.
In some cases it may be absolutely
tiecessary to send a party in advance to
erect monuments of stone, or signals of
timber upon proposed stations which are
at the same time important and unfavor-
able for observations; or, should the
mountain be covered with forest, it may
be necessary to send axemen to clear
away all but the largest and most cen-
tral of these trees. Such action, how-
ever, causes a vexatious delay on the
part of the engineer, and is contrary to
the fundamental principles of this
method of survey, whose work should
be a steady and unretarded progress,
and should be reconnoissance and com-
pletion in itself.
From the top of his first high mountain
station the engineer sees his allotted
territory spread out before him, and he
immediately begins to lay his plans for
the coming season. He selects two dis-
tant peaks, which, with his present
station, will form a grand triangle. Be-
yond these, far in the distance, there is
yet another, and these four constitute a
great quadrilateral, the lengths of whose
diagonals may each be determined by
two independent sets of observations,
checking each other. In like manner
he makes the circuit of the horizon, util-
VAN NOSTRAND' S ENGINEERING MAGAZINE.
izing, as best he can, the peaks which
rise around him.
Although, owing to the many obsta-
cles and unforeseen difficulties which are
experienced in traveling through an un-
known country, he may be compelled to
modify and alter his first plans very
often, yet as soon as he abandons one
feature of his scheme he immediately
adopts a substitute to take its place.
To be provided for such an emergency,
if a distant peak, as,f or instance,one of the
sharp pinnacles of the Organ Mountains,
should appear impossible of ascent, he
will select another in the same vicinity,
and consider that as an alternate to the
first, reading angles to it and treating it
in all respects as a regular station as
long as such a reserve may seem neces-
sary.
In proceeding from one mountain to
the next he surveys all of the interme-
diate country, his course being governed
by the advantages and obstacles whieh
present themselves from day to day.
His route should never be an arbitrary
one, determined at a distance and weeks
beforehand, but he should be free to act
upon the spur of the moment, following
a stream to its source here and suivey-
ing a lake there, according as these geo-
graphical features may be encountered.
If these features are depicted on maps
already made, then there is no need of a
second survey of the country; if they
are not, he is not likely to know of their
existence until he finds them.
EQUIPMENT OF THE PARTY.
Since the terminus of a day's survey
cannot always be advantageously decided
upon, even in the morning on which it is
begun, it is especially desirable that the
party may carry with it its own equipage
and supplies, so as to be prepared to
camp anywhere that night may over-
take it. As it is a part of the policy of
geographical work that the engineer
should never follow the same route
twice, a survey carried on by daily ex-
cursions from fazendas, settlements, or
other fixed points of supply, returning
to this base by the same road in the
afternoon, would cost a great waste of
time and energy. The necessary outfit
of a scientific corps, consisting of instru-
ments, clothing, cooking utensils, and
provisions, can be carried by a train of
pack-mules equal in number to the peo-
ple whom they accompany. With this
equipment the party are independent,
and can camp anywhere that wood for
fuel, forage for the animals, and a sup-
ply of water are found. This arrange-
ment is particularly necessary in the
occupation of a mountain station, upon
which, for successful observation, it may
be imperative to arrive at an early hour
in the morning and to remain through
the greater portion of one, two, or three
days. From a camp near the summit
this may be reached in an hour or two;
but from a distant base almost the en-
tire day would be consumed in the jour-
ney to and fro.
THE TRIANGTJLATION STATION.
The mountain will be ascended by the
engineer, the meteorologist, and such
assistants as may be required to carry
the implements of the work and the food
and water necessary for the maintenance
of the party, and to build the stone
monument, which, if possible, should
always crown the peak, to receive the
records deposited here, to assist in the
future identification of this station, and
to serve as an object upon which to
direct the telescope in subsequent ob-
servations. One day will be a sufficient
time of occupation for the ordinary
triangulation station, provided the
weather be favorable. To the more
important ones, however, it may be
advisable to devote two days, spending
one night upon the crest in astronomical
observations for the determination of
the azimuth of some line radiating from
here; this will serve as a check upon its
computed value, as derived from the
original azimuth determination made by
the astronomer at the base- line. In
times of high wind, or cloudy and stormy
weather, especially liable to occur upon
the summits of peaks, it may be several
days before satisfactory results are ob-
tained, and therefore the party should
always go well equipped for a prolonged
stay in their mountain camp.
PROFILE SKETCHES.
As an economy of time, whieh is of
the greatest value here, the observer
should make all reasonable haste in his
operations. Especially is this so in his
sketches, over which he must not linger,
which, if he is anything of an artist, he
GEOGRAPHICAL SURVEYING.
67
will be sorely tempted to do. He may
see before him broader views and
scenery more grand and impressive than
ever was painted yet, but picturesque
effects are no business of his. To the
geographer of artistic tastes there is
great temptation to finish his sketch by
inserting a pine-tree in the foreground,
and, perhaps, an eagle's-nest in the tree;
this is all very wrong, as such dalliance
may cost the omission of that far distant
peak, which is printed like a fine point
against the horizon, and which, insignifi-
cant and low as it appears, is yet of
vital importance to his scheme.
His sketch is perforce but the outline
and skeleton of a picture. Two con-
verging straight lines, with a few strokes
of shading, hastily thrown in, are suffi-
cient to represent the ordinary mountain
peak. Yet, if the peak should possess
any oddity or marked individuality of
shape, this feature should be preserved
and even magnified in the drawing, as a
key to the identification of this point
when seen from elsewhere at some other
time. Since any mountain, from differ-
ent points of view, presents phases that
are quite dissimilar, it is one of the
greatest difficulties of triangulation to
make sure of the identity of a station
previously occupied, or, where there are
a number of observers in the field, to se-
cure uniformity in the choice of the same.
CONTOUR DRAWINGS.
The expert geographer is proficient not
only in rapid profile but also in contour
drawing, and on every mountain station
he executes a contour plot of that scope
of country which he sees beneath his
feet, and of whose conformation he is
reasonably certain. But in the prepara-
tion of this local plot he should not be
too comprehensive, and go beyond the
bounds of certainty into the outer limits
of conjecture. Every mountain is sur-
rounded by valleys, on whose farther
side are other ranges perhaps as high as
this, and they form the limit beyond
which no contour sketch should presume
to go, else it becomes conjectural and
unreliable. It may include those en-
virons of valleys, with a periphery of the
foot-hills which are beyond them, and an
indication of the canons which indent
the same, but no more.
In the office a contour sketch is ac-
cepted as truthful evidence of the ground
as it really is, while a profile drawing is
considered only a copy of the country as
it appears to be, when uncorrected for
the illusions of perspective, and is studied
and deciphered accordingly. Looking
abroad from this station, the successions
of distant ranges, which are in reality
separated by broad interspaces of valley
and plain, are projected into a dense and
circular wall, apparently unbroken by
pass or intermission, whose serrated out-
line is seemingly as continuous as the
horizon. It is an error to which the
human sight and judgment are subject,
and so, in orographic delineation, the
impressions of the eye are to be received
with caution, and only the readings of
the theodolite are to be accepted in full
faitH.
PHOTOGRAPHS.
As a supplement to the pencil of the
engineer, the photographer's camera can
often be used to good advantage, in se-
curing, in their true proportions, the
many details of geological structure
which are necessarily omitted from a
hasty sketch. In the best geographical
delineation of a country, a series of
photographs are almost indispensable,
as, aside from affording much material
for the filling in of a map, they reveal
the nature of the surface which they
represent, showing whether it is regular
or broken, well-preserved or eroded,
whether a cliff is impassable or easy of
ascent, and whether a coast is smooth
and sandy, or irregular and rocky. All
of these conditions should be made to
appear in every good map, whether in
contour lines or hachures, and particu-
larly so, when, as in this case, the map is
intended as a basis for geological repre-
sentations.
READING THE ANGLES.
The instrument of triangulation is a
theodolite, whose accuracy and weight
increase with the minuteness of the
graduation, but, in this work, in which
rapidity and ease of transportation are
to be considered, there comes a limit be-
yond which it is imperative to sacrifice
nicety to portability. This is reached
when the limb is graduated so as to dis-
criminate to ten seconds of arc, between
which divisions the observer may esti-
mate to every intermediate five seconds.
VAN NOSTRAND'S ENGINEERING MAGAZINE.
With this he reads and repeats the
angles, singly and in combinations, that
lie between the visible points of the
triangulation scheme. It is advisable to
make at least six determinations of each
angle upon each of the two verniers of
the instrument, amounting to twelve
repetitions in all. The greater the num-
ber of readings from which the mean is
derived, the less will be the probable
error of observation affecting that mean.
The observer may complete the repe-
tition of each angle by itself, or, what is
more convenient, he may read them in
conjunction, by making six complete cir-
cuits of the horizon. In either case the
graduated limb of the theodolite will be
turned 30° in azimuth at every return to
the initial point. In this manner each
angle is read upon twelve different and
equi-distant divisions of the circle, and
the faults arising from eccentricity or
imperfect graduation are reduced to a
minimum.
The most opportune moments of the
day will be devoted to this important
test, and all other duties will be neg-
lected for this. Successful triangulation
demands perfect quiet and a clear hori-
zon. In a dense and hazy atmosphere,
or in a region of low clouds, the observer
may find his opportunity in the evening
or early morning, when the sun is be-
hind the hills, and the rim of the earth
is seen in silhouette against the rosy
background of the sky.
SUBORDINATE ANGLES.
Upon the triangulation station the
engineer also reads angles for the direc-
tion of the spurs which project from
here and of the streams that debouch
from here, estimating the distances of
geographical features in his immediate
vicinity. How far he may trust to his
judgment in this respect, will be determ-
ined by the circumstances by which he
is surrounded. It is the engineer's duty
to make the best map of a country that
is possible with the advantages at his
command, and if he should see before
him' a tract of country, distant even ten
or twenty kilometres, which he will
never see again, he should take note of
it on his contour plot; but if he knows
that some future route of his will cross
it, he can afford to neglect it now.
In addition he takes readings to infe-
rior elevations which, although they
may never be occupied for reciprocal ob-
servations, may yet be located by
intersections from two or more triangu-
lation stations. Some point, or " tit,"
standing on the edge of an abrupt bluff,
where the rapid descent begins, is used
as a means of marking the end of a
neighboring mountain range. A solitary
butte on the plain, insignificant in itself,
is very useful in determining the locus
of the stream which flows by the side of
it. A promontory, jutting into the con-
fluence of two rivers, is instrumental in
fixing the place of their union. Sights
are also taken to the junctions of
streams, the mouths of canons, and to
the church or other central object of a
distant village. A spot of green on the
desert, evidence of a spring of water
there, is located, for it will perhaps be
camping-ground some day for himself or
his co-laborers. A minute patch of
white lake-bed, or red escarpment, or a
solitary tree, is sighted upon, because on
such a day he made an odometric sta-
tion there, and this sight will serve to
check his position.
NOMENCLATURE.
In his note-book and mind he has
dubbed all of these things with graphic
titles, or designated them by letters of
the alphabet, and by these tokens he will
know them when he sees them again.
But this system of names is only a
transient device for the assistance of
himself and those who work in concord
with him, and should not appear upon
the printed sheet to the exclusion of the
native and established nomenclature of
the country, which should be investigated
as far as possible, and, upon the final
maps, should be adopted in preference
to the arbitrary naming of any one man.
The usefulness of a map, as a guide to
the traveler, is in a great degree invali-
dated by a nomenclature which is at
variance with that in use upon the ground
itself. Perhaps the modern geographer
is guilty of no more common and high-
handed outrage against right, conven-
ience, and beauty, than by ignoring the
appropriate titles which abound in every
country, however wild and uncivilized,
and attaching his own, or by mutual and
tacit agreement, the names of his com-
rades, to the mountains of that land,
GEOGRAPHICAL SURVEYING.
69
thus announciDg themselves to the world
as nostrums are advertised on the pyra-
mids.
THE TOPOGRAPHICAL STATION.
All of the preceding description that
does not refer to the triangulation pro-
cess is also pertinent to the topographical
station. This term is applied to those
isolated stations of survey, apart from
the route of the odometer, and interme-
diate to the points of primary triangula-
tion. They are more numerous than the
primary stations, being^usually scattered
over the country at intervals of not
more than twenty kilometers, but are
less important, since there is no great
responsibility of accuracy resting upon
them. The topographical stations cor-
respond, in position and numbers, with
the secondary triangulation stations of a
more elaborate geodetic survey.
A SECONDARY TRIANGULATION.
Even here the topographical station
may be made a point in a subordinate
scheme of triangulation if its situation is
elevated, distinct, and capable of recog-
nition from a distance. Of course, it is
desirable that every occupied station
should subsequently be made an object
of reciprocal observations, and the engi-
neer should neglect no opportunity to
confirm his position in this manner.
Each point thus fixed becomes the center
of a plexus of triangles, of each of which
the three angles have been observed;
the total error of observation in these
three angles becomes apparent, and the
computer is enabled to distribute it judi-
ciously among them before he proceeds
to the computation of the sides.
For this reason the observer upon any
topographical station will make careful
search for other points which he may
have occupied or may contemplate oc-
cupying, and will be more than usually
cautious in reading angles to them. On
his return to the office, at the end of the
season, he will pick out from the multi-
tude of his notes as many complete tri-
angles as he may have observed, and
these will be so much gain attained at a
cost of but little extra labor. But if he
makes it imperative upon himself to
carry on a complete and systematic tri-
angulation within the first, the additional
refinement gained will by no means com-
pensate him for the disadvantages of
reconnoissance and delay which this in-
volves.
It is safe to say that it is a longer and
more laborious work to accomplish an
unbroken secondary triangulation than
a primary, as the stations are more nu-
merous, less elevated and conspicuous,
and oftener in the shadow. On the
other hand, the results are by no means
so valuable. The primary triangulation
sustains the general and continued accu-
racy of the survey; the secondary does
little more than to insure the individual
positions of its own stations.
POSITION OF THE TOPOGRAPHICAL STA-
TION.
Although not necessarily a point in
the triangulation proper the site of the
topographical station must afford angu-
lar data sufficient for the determination
of its position by the three-point problem*
After that, its predominant idea is that
it is a means of local geography, or to-
pography, and a center for a series of
contour sketches. In addition to these
detailed plots of the country in the im-
mediate vicinity, profile drawings of the
more distant regions are made. Then,
by lines of sight, which shall be intersect-
ed by other rays from other topographical
or triangulation stations, the most
prominent features within a radius of
twenty or thirty kilometers are crossed,
and, as a precaution, angles are also read
to all eminent points visible at a greater
distance, even to the horizon, as they
may come into use in some future di-
lemma in map-drawing.
While the sight of the topographical
station should be as elevated and marked
as possible, yet any hill, however humble
and inconspicuous, or even the level sur-
face of a plain, may serve this purpose,
provided that there be three triangula-
tion stations, or other known points, visi-
ble, and there is any useful information
to be gained by lingering here. A few
hours are usually enough for its occupa-
tion, and the route between points of
triangulation should be marked at regu-
lar intervals by the monuments of these
stations. It is a good plan for the en-
gineer to make a practice of diverging
from his route at some point in each
day's odometric survey, and, ascending
a suitable eminence close at hand, make
a topographical station there. As far as
70
VAN nostrand's engineering magazine.
a general rule can be given for the oc-
currence of mountain stations, it is advis-
able for the party to advance by linear
survey every second day, remaining in
camp on each alternate day, while the
engineer ascends some peak in the vicin-
ity for the purpose of establishing a
topographical or triangulation station
there.
The large triangulation theodolite
should be used in the more important
topographical stations, or those which
may possibly be treated as points in a
secondary triangulation, but for the sake
of convenience, the small route transit
must be made to suffice for those which
are made in the course of the daily
march.
THE ODOMETRIC, OK MEANDER SURVEY.*
The meander survey is useful as an
adjunct to the triangulation, filling up
its skeleton with that detailed informa-
tion which alone can give practical and
popular value to a map. It determines
the courses of valleys and streams, the
routes of roads and trails, the peripheries
of lakes and basins, and the distances
between springs of water, villages, areas
of pasture, fords of rivers, and other
points of interest to the future traveler.
Finally, it is a commendable occupation
for the engineer while on his way from
one mountain station to the next, and,
since it occasions no delay in the general
progress of the work, as the engineer
can, as a rule, meander as much road as
* Note to the Portuguese Edition. — Tbis term which is
now firmly grounded in the technical language of
geographical surveying in the United States, is a mis-
nomer, and therefore, in introducing a corresponding
one into the Portuguese, it will be well to adopt some
more appropriate expression. For the reason, "odomet-
ric survey" will be used to designate line surveys in
which the odometer takes part, and " route survey "
(caminhamento i as a general term, to include not only the
above, but also those in which distances are determined
by time, by the chain where that metbod is employed, or
by paces, 'whether of man or horse, and whether re-
corded by the pedometer or by direct counting.
As the meander survey is understood, where this ex-
pression is used, it is simply any survpy following a zig-
zag line, whose angles in general, are alternately salient
and re-entrant, as the line accommodates itself to the
route of travel. But this word " meander," having been
derived from the river of the same name, in ancient
Phrygia, which was celebrated for its windiDg, sinuous
course, literally means, " abounding in curves." It will
thus be seen that the more a survey approaches to a true
meander, the farther it departs from the first principles
of accurate linear surveying, which dictate that it shall
consist of straight lines and angles only. Since it is al-
ways to be regretted when a survey is confined to a true
meander line, as for instance, in tracing the course of a
road along and up the side of a mountain range, so it is
also a matter of regret that this word should have been
introduced into the language of engineering, apparently
sanctioning a faulty survey.
his pack-train can travel in one day, its
results are net gain to the survey.
In the theoretical journey of this kind,
the engineer would follow the edge of
the dividing ridge from one station to
the next, from which lofty promenade
he could see the earth like an extended
scroll beneath his feet, and make a sur-
vey that would be exhaustive and
complete. But in the real, hard prac-
tice, he finds this path an impracticable
one, for it is broken by precipices and
blocked by abutments often a hundred
metres or more in height. His easiest
route of travel is by the side of flowing
water, whose tendency it is to evade ab-
rupt cliffs and soften steep gradients
into an average and even slope. Be-
sides, along the streams there are trails
made by the wild animals which come
here for drink and covert, and by the
people of the country who come hither
to hunt and fish. Therefore, if the de-
tour be not too great, the most expedi-
ent route from mountain to mountain, is
down one valley and up another, and
the geographer who traverses a valley
without taking some sort of a survey of
it, is culpably negligent of his duty.
On the other hand, if in a block of
mountains the pre-eminent peaks be oc-
cupied, and the streams which emanate
therefrom be meandered, nothing more
is needed for a most excellent geograph-
ical map of that country.
THE MEANDER TRANSIT.
It is supposed that all transportation
of outfit, and all travel, even in the me-
ander survey, is accomplished on the
backs of horses or mules. Riding in
the saddle, the surveyor can devote but
one hand to the grasp and protection of
his instrument, the feet of whose tripod
rest in a holster attached to the left
stirrup. To facilitate his secure hold,
the members of the tripod are thirds of
a cylinder, which fold into the smallest
possible compass, and are easily held in
the grip of one hand.
The instrumental part of the meander
transit is neat, solid, and compactly
constructed. Its graduated limb is of
small diameter, and its horizontal ver-
nier reads to minutes only, which is all
very well, since no smaller divisions can
be plotted on the map. This graduation
is used in the occupation of topograph-
MAXIMUM STRESSES IN FRAMED BRIDGES.
71
ical stations, at those meander stations
where the view is extended enough to
make it profitable to linger an hour or
so in the accumulation of notes and
sketches, and at all those which are
three-point stations as well. But in the
general survey, not the vernier-plate,
but the compass needle, is used, on ac-
count of its greater convenience. The
compass box is graduated, from zero at
the north, around by the left to 360° at
the north again, so that a reading of 90°
corresponds to magnetic east, and 270°
to west. The field records are kept
in this manner, and in the office the de-
clination of the needle is first applied to
each bearing, after which it is reduced
to its true direction, preparatory to the
plotting.
MAXIMUM STRESSES IN FRAMED BRIDGES.
By Prof. WM. CAIN, A.M., C.E.
Contributed to Van Nostrand's Magazine.
I.
The writer has made the endeavor in
the following pages to investigate, for
the live loads assumed, the maximum
stresses that can ever occur in the chords,
as well as in the web members of a
bridge; also the most economical height
of trusses. In so doing he has necessa-
ily gone over some old ground; in the
briefest manner, however, consistent with
logical development; and has compared,
approximately, some leading American
types of bridges as regards weight. The
unit strains were determined by the
modification of Launhardt's formula, pro-
posed by the writer in the November,
1877, number of this Magazine, which,
it was thought, was peculiarly adapted
to the comparison of trusses, besides il-
lustrating the " new method " of desig-
nating " Structures of Iron and Steel,"
which may possess interest at this time.
1. A Framed Bridge is generally com-
posed of two or more trusses or frames,
as A<2B, Fig. 1; which lie in vertical
planes, and are connected together by
bracing, including the floor beams, on
which longitudinal stringers rest, which
support the cross ties and rails of a rail-
road bridge or the flooring of a highway
bridge.
The upper and lower horizontal mem-
bers of a truss are called respectively,
the upper and lower chords, the bracing
between them the web. The members of
the web that act always as ties are called
main ties • those acting always as struts,
main braces or posts / and those mem-
bers that act alternately as ties and struts
are called counters — a term likewise ap-
plied to pieces' that are not strained ap-
preciably by the dead load or any uni-
form load on the structure, but are
strained when the live load is distributed
in a certain manner.
2. As the roadway is supported by the
top or lower chord, the bridge is called
a deck bridge or a through bridge. The
intersection as a, Fig. 1, of a web mem-
ber with a chord is called an apex. The
distance from apex to apex on the same
chord will be called a panel length, a
panel being the part of the bridge so in-
cluded.
The truss, Fig. 1, rests upon abutments
at A and B and is unsupported at the dis-
tance or space AB.
The pressures exerted by the truss
against the abutments are resisted by
their reactions V, Yl5 equal to them, on
the principle that action and reaction are
ever equal.
4. The following suppositions, only
approximately realized in practice, will
be made :
72
VAN NOSTRAND'S ENGINEERING MAGAZINE.
The reactions V, Vl9 will be assumed
to be vertical.
(Bow, in his " Economics of Construc-
tion," has given many illustrations of in-
clined reactions, due to friction at the
abutments, resisting expansion or contrac-
tion of chords. Its influence is generally
small when the end of the bridge rests
upon rollers.)
It is assumed that the bridge members
are jointed, or free to move, at the
apices, and that the resultant resistance
offered by each piece coincides in posi-
tion and direction with the straight line
connecting the joints or apices of that
piece.
For the computation of the chords,
main ties, braces and counters, the weight
of bridge and load will be considered as
concentrated at the apices of the chord
that bears the roadway, the weight one-
half panel either side of an apex a, on
and over ab and be being considered con-
centrated at the apex a.
Other suppositions will be noticed
further on.
5. In Fig. 1, wlf w2 . . . ., are the panel
weights on one truss due to the weight
of the bridge or dead load, w6, w>7, the
panel weight due to live load at the cor-
responding apices.
Call the horizontal distances from wl9
w2, . . . ., to B, ll9 Za, . . ., respectively.
Now it is a law of Mechanics that when
any number of forces acting on a rigid
body and in the same plane are in equi-
librium, the algebraic sum of their mo-
ments about any point in the plane of the
forces is zero.
Take the point B as the center of mo-
ments y then since V acts upward and
the weights wx, w2 . . . . downwards.
VxAB-KJ1 + waJ9+ . . .)+VaX0=0,
or denoting (w^ + wj^ . . .) by 2wl, 2
denoting sum of similar quantities, we
have,
AB
(1)
The above law of course holds if we
take moments about a, or any other point
in the plane of the truss.
6. Again it is a law of parallel forces
in equilibrium that their algebraic sum is
zero.
.'. V + V-2w=0 . . (2)
2w being put for (w1 + wi+ . . .).
When one reaction then is known the
other can always be found.
The reactions V, VlS with the weights
of bridge and load wl9 w2, . . . are called
the external forces.
V. Now suppose the truss cut along
the line de : conceive forces C, R, T, ap-
plied at the cut parts equal and directly
opposed to the resistances of those mem-
bers, and let the part of the truss be-
tween B and de be removed. Then call-
ing the sum of the weights wl9 w2 . . .
between A and de, 2w; the forces C, R,
T, V, 2w, must hold the part of the
truss between A and de in equilibrium,
since C, R and T are equivalent to the
action of the external forces to the right
of the section de.
8. Denote the vertical component of
R by S, its horizontal component by H.
Call the forces V, 2w, C, R, T, the act-
ing forces. Then from Mechanics the
algebraic sum of their vertical compo-
nents equals zero
.-. Y-2to=S ... (3)
Also the sum of the horizontal compo-
nents of the acting forces equals zero?
.-. C + H=T ... (4)
S, the vertical component over any
panel is called the shearing force for
that panel and is always equal to the re-
action V—, the sum of the downward
forces from A to the section considered.
9. If i denote the inclination of the
web member cut to the vertical then S
sec. i is the total stress on the web mem-
ber.
From eq. (l), we find V; from eq. (3)
S, whence the stress on any web member
cut follows.
10. Note that ipS=V— 2w is +, the
resistance of web member cut acts in the
same direction as V, i.e. upwards; R acts
MAXIMUM STRESSES IN FRAMED BRIDGES.
73
downwards, and the strain on the tie-brace
cut is compressive if its top leans away
from the abutment A; otherwise tensile /
since in the first case H acts to the left,
in the last it acts to the right in order
that R, the resultant of H and S may
act in the direction of the web member
cut as was assumed. Let the reader con-
ceive de removed one panel to the left
and illustrate the last case with a draw-
ing. Also the two following.
11. When V—2w is — , then S acts
upwards, therefore, a web member whose
top leans towards A is compressed, other-
wise it sustains a tensile strain.
The last two cases occur, for a uniform
load when the section de is taken to the
right of the center.
These rules are especially useful in
treating continuous girders or draw-
bridges.
12. Maximum Strain on Web Mem-
bers.— The strain is greatest when the
corresponding S is greatest; and S is a
maximum when the live load, the heaviest
part in front, extends from the farthest
abutment to the panel considered (de Fig.
(a.) For if any live load rests on the
portion Ade (Fig. 1), V is increased by a
part of it only, whereas 2w is augment-
ed by the whole of it, hence S=V— 2w
is less than before.
(b.) Again, if any load on part Bde
is taken off, V is diminished, but 2w is
the same as before, hence S is less than
before.
(c.) If the live load, distributed as be-
fore, is placed with its front at the apex
to the left of de and extending to the
nearest abutment A, then Va<V and
since 2w between B and de is greater
than 2io to left of de therefore, S=V—
2w is less than before.
(d.) The heaviest part of the live load
must be in front, for then V is greatest.
We conclude as was enunciated.
13. In case (c) if the stress caused in
a web member is of an opposite kind to
that caused by the maximum shearing
force, the member must be designed to
resist alternately both stresses, or a
counter must be added to the panel con-
sidered.
14. Live Load. — On this subject, see
Van Nostrand's Magazine for October,
1875, p. 305; also for May, 1877, p. 476;
also the " Illustrated Albums " of many
bridge companies.
The locomotive assumed for railroad
bridges, in what follows, concentrates
84,000 lbs. on six drivers, three on each
side, on a twelve feet wheel base. The
locomotive and tender covers fifty feet
of track; the thirty-eight feet not cov-
ered by the drivers before and behind
the engine is supposed loaded with 2,000
lbs. per foot .*. total weight of locomo-
tive and tender is 84000 + 38 X 2,000
= 160,000 lbs.
15. Computation of Floor Beams and
Stringers. — The floor beams extend from
an apex of one truss to the correspond-
ing apex of the other truss. The string-
ers resting on them lie under the rails or
parallel to them.
Then for six feet panel lengths and
under, the center drivers can concentrate
84000 — 28000 lbs.*on floor beam or at
center of stringers.
For twelve feet panels, let the center
drivers rest on floor beam; the front and
rear drivers being at center of adjacent
panels, one-half their weight is supported
by a floor beam. Its reaction from the
2000 X 6 lbs. in front and behind drivers=
2000X6 , n ,
2 = 6000; so that the floor beam
4
sustains in all 28000+28000+6000=62000
lbs. The stringers sustain 28000 at cen-
ter, assuming that they are most strained
when the center drivers rest on their cen-
ter. For greater panels than twelve feet,
assume approximately the 2000 lbs. per
foot, extending from front and rear driv-
ers to the nearest floor beam, and reduce
the load to an equivalent center load P
for the stringers load. Thus for a panel
length of twenty feet : Moment at cen-
ter due to P is |P^=5 P. The moment
at center due to the actual load is, 50000
X 10 — 28000 X 6 — 8000 X 8 = 268000;
which, equaled with the other moment,
gives P=53600.
The maximum loads'on floor beams are
Concentrated directly under the rails and
are found by supposing center drivers to
rest directly over floor beam. See arts.
43, 44 further on this subject. The fol-
lowing little table is made out on the
above basis, and is intended to give aver-
age results :
74
VAN nosteand' S ENGINEEKING magazine.
Length of
Panel.
6 feet & under
9
12
15
161
20
Floor Beams.
28000
48666
62000
72400
77492
86800
Stringers equal
to center load.
28000
28000
28000
38467
44987
53600
16. Live Load for Web Members and
Chords. — The live load assumed for web
members consists of two locomotives as
above on 100 feet; there being not less
than fifty feet between center driving
wheels of locomotives; followed by cars
weighing 2000 lbs. per foot for rest of
span. For panel lengths over twelve
feet, the disposition is as in Fig. 3, the
2000 lbs. per foot in front of drivers ex-
tending to middle of panel. For panel
lengths less than twelve feet, the loco-
motive will be supposed to be without
truck wheels in front and hence no
weight is assumed before drivers. The
locomotive excess over 2000 lbs. per
foot is 8400 — 12X2000 = 60000 or 20000
lbs. on each pair of drivers; hence we
assume for web members the bridge loaded
with 2000 lbs. per foot up to the middle
of the panel considered, and a locomotive
excess of 60000 lbs. at foremost apex, also
60000 lbs. fifty feet back of this; or a
greater distance if the strains are thereby
greater. For chord strains, we assume
the bridge loaded with 2000 lbs. per foot
over the entire span, and with the locomo-
tive excess, consisting of two weights of
60000 lbs. each not less than fifty feet
apart; the latter to be so placed as to give
maximum stresses on each chord panel in
turn, as will be fully shown in the sequel.
Fig. 3
( N - n)l
17. If truck wheels are assumed in
front of drivers, the shearing force is less
than for the disposition above. For
short spans especially, it seems desirable
to assume as above that the foremost
engine has no truck wheels, i.e., when
the panel lengths are less than 12 feet,
or practically even for greater panel
lengths.
1 8. Web Strains. — In Fig. 3,
w= weight per panel of one truss with
its share of roadway and cross brac-
ing.
p— weight per panel of cars[=(1000 I)
pounds] for one truss.
1= length of panel in feet.
E=locomotive excess (=60000 lbs.) for
one truss.
c= distance from front apex to its cen-
ter of gravity (25 ft.)
N=number of panels (12 in Fig.)
7i= No. panel considered, numbered from
A as in Fig.
^inclination of a tie or brace to the
vertical.
Now to find the maximum shearing
stress over the nth panel (5th in Fig.)
by art. 16, the car load, 1000 lbs. per foot
must extend to the middle of the nth
panel; we also have, 30000 lbs. at apex
on right of nth panel and 30000 lbs. 50'
to the right of the last. Next (Art. 4),
the car load ^ panel either side of an
apex is regarded as concentrated at that
apex.
19. Now take the right abutment as
the center of moments. The lever arm
of V is N£. There are (N— l) weights w,
whose resultant acting at the center of
the span, has a lever arm =^Nl. There
are (N— n) weights p, whose center of
gravity is i(N— n + l)l from right abut-
ment (-J Ba in the Fig.) and lastly the
locomotive excess E has a lever arm,
m-(nl+c)
Therefore art. 5,
VNZ= (N-l)w|N£+ (N-n)p(N-n+ 1)
L + E[m-(nl+c)]
Or calling the shearing force over the nth
panel Sn> we have, art. 7,
( w
Sn =zV-{n-l)w = J (N-2» + l)-
+ (N-») (N-» + i) JL+|-(N_£-») |
(5)
When the rearmost engine is hot on
the bridge, E, in the preceding formula,
becomes 30000 lbs. and c — o.
MAXIMUM STRESSES IN FRAMED BRIDGES.
75
20. Having found maximum S over
each panel, as e.g., the 5th, the stress on
the post = S sec. i, that on the tie is S
sec. tj ; i and \ denoting the respective j
inclinations of the post and tie to the
vertical; art. 9. There is the same shear- j
ing stress on tie and brace over the same
panel, and this evidently (see the reason-
ing of art. 7) holds when the posts are I
vertical as in the Pratt Truss, or the ties
vertical as in the Howe Truss, or when
the ties and braces are equally inclined
as in the Warren Girder, or unequally
inclined as in the above figure. We shall
use this equation in discussing the bow-
string and other forms of girder likewise.
An example will best illustrate the use of
the equation and the theory of counters.
21. Example. — Let the span AB=200
feet, divided into N=12 panel lengths
of 16' 8" each; weight of bridge 336000
lbs. or 168,000 lbs. to each truss .'. to—
j^sojlo — 14000 ; live load as in art. 16
.-. jt?=1000 £=£00-^, since l=$g-\ E=
60000, c=25. Substituting these values
in formula (5), we get :
Sn=(13-2n) 7000+(12-
-n) (13 -n) 694+(10£-7i) 5000.
S
A,
A2
Si =
77000-
[-11x12x694+47500=
216108
34268
—
£3 =
63000-
[-10 x 11x694+42500=
181840
32880
1388
s3 =
49000-
- 9x10x694+37500=
148960
31492
1388
s4 =
35000-
\- 8x 9x694+32500=
117468
30104
1388
sR =
21000-
- 7x 8x694+27500=
87364
28716
1388
s6 =
7000-
- 6x 7x694+22500=
5864S
27328
1388
s7 =
- 7000-
h 5x 6x694+17500=
31320
25940
1388
s8 =-
-21000-
h 4x 5x694+12500 =
5380
24552
1888
: ^9 =-
-35000-
\- 3x 4x694+ 7500 =
-19172
—
—
Sio = "
-49000-
- 2x 3x694+ 5000=
-39836
—
—
Sn=-
-63000-
- lx 2x694+ 2500=
-59112
—
—
£>12=="
-77000
=
-77000
—
—
The rearmost 30000 locomotive excess
leaves the truss for S9, whence the for-
mula is then modified by putting c=o
and E=30000, to compute S9, S10 and Sn.
22. The common differences for the
terms (13 — 2?i) 7000 and (10J— n) 5000
are 2 X 7000 and 5000 respectively; from
which those terms are quickly computed.
Column A , is found by subtracting each
value in column S from the preceding
value. Column A 2 is the common differ-
ence of the quantities in column A ,. In
fact if in the proceding equation we
change n to n + l and subtract the last
equation from the first we get,
(S„ - Sw+1>=-^+ (w+p + ^y
the equation of a straight line which
makes an angle with the axis of abscis-
sas (;i)whose tangent is — ^.
Giving values to n : 1, 2, 3 the
difference between successive
common
values is, A
and A2; by reversing the above method
:^. On computing Sx A
of deducing columns A , and
find the various values of S.
23. The "shears" may be found
graphically if desired by drawing the
straight line given by the equation
above, taking off in dividers the differen-
ces between successive shears (Sn — » Sn+i)
which are represented by the ordinates
to the line and subtracting these first
differences in order from the line taken
to represent S1? thus giving lines which
measured to a scale will give S9, S, . . . ,
provided always that both engines re-
main on the bridge.
Thus making ro=l, we have
(S-S.):
p E
for the difference between the shears in
the first and second panels. Lay this
difference off vertically above the'lower
apex one panel to the right of the left
abutment, regarding the lower chord as
the axis of abscissas (n). Also lay off
the value (S6— S.), say, at the 6th apex
from the left abutment; the line joining
the extremities of these ordinates will
cut off the successive differences A 1 from
76
VAN NOSTRAND'S ENGINEERING MAGAZINE.
ordinates erected at apexes 2, 3, 4,
These ordinates, can be laid off successive-
ly on the line equal to S, by scale; thus
giving S9, S3 . . . . , as before mentioned.
24. Having thus found S1? Sa, . . . ,
the strains in the web members over
panels 1, 2, .... are Sa sec. i, S2 sec. i,
. . . . When a web member over the
nth panel becomes vertical, its mass
strain is simply Sn . If we form a col-
umn, S sec. i, to the right of column S
(art. 22), and deduce A, and A 2 from it,
we detect any error that may occur in
multiplying by sec. i.
By art. 10, when Sn is + , the web
members whose tops lean away from A
act as struts; those whose tops lean
toward A as ties. In this case, S is +
for the first 8 panels, or 2 panels past
the center. Now if the live load is sup-
posed to move on from A toward B, we
prove similarly that the web members
whose tops lean j ™%J™ } B act as
•! .. > .< Therefore each web mem-
( ties j
ber, in this case, in panels 5, 6, 7 and 8,
suffers both compression and tension in
turn and must be designed for the maxi-
ma of both strains, i.e., counter braced.
This max. S over the 5th panel is when
the live load extends from the farthest
abutment, and equals S5= 87364. But
when the live load extends from the
nearest abutment to the 5th panel from
that abutment as from B to panel marked
8 in Fig. 3, S=S8=5380; and, as just
shown, the web members previously
designed as] S^™gtS I for S= 87364, must
now be designed as < *es > for S =
5380, also. Similarly the web members
of panel 6 are designed as j . !• f or a
{ties )
* 4. r
struts j
for a maximum stress of 31320 sec. i.
We then design the web members up to
the middle of the truss for the max.
stresses, and those panels past the center
for which S is positive, which may be
numbered now from the other abutment,
if preferred, (after S is found by form
5 by its numeration), have their web
members designed for the lesser stresses
of an opposite character to the maximum
stresses.
25. If preferred, in place of causing
the same piece to act both as a strut and
a tie, we may insert a counter in the
panel to beat one of the strains, design-
ing the main ties or braces of that panel
so that they cannot take a reverse strain
and the inserted member is thus com-
pelled to take it.
Thus in Figs. 5 and 6 the dotted lines
are counters that bear but one kind of
strain, like the main ties and braces of
the truss.
26. When the live load, engines m
front, extends from the farthest abut-
ment, Sn is a maximum for the *eth panel
by art. 12.
When the live load, engines in front,
extends from the nearest abutment to the
wth panel, S being +, the strains induced
in the web members of the #tth panel are
a maximum of an opposite character to
the first.
The proof is the same as in cases a, b
and d of art. 12.
27. When the load extends from the
nearest abutment and Sn {of eq. 5 is —,
as in panels 9, 10, 11, 12 of bridge as-
sumed, the strains are not reversed (see
art. 10), but we find from eq. (5) the
minimum strains that can ever come on
the web of the panels considered.
Thus we see in the example, art. 21,
that S9, S10, Sn, are less numerically than
if there is no live load on bridge, for the
w
term (N— 2n + l)— involving the dead
load is — when n>JN, whereas the two
terms involving the effects of the live
load are always positive.
Then, reasoning as in art. 12, we see
that the positive terms are less for any
live load in front of panel considered, or
for any live load taken off behind the
panel, and that the locomotives must be
in front, therefore Sn is least numerically
when the load, engines in front, extends
from the nearest abutment, Su being
negative.
28. Observe that for a dead load alone,
p—o, E — o, that Sn = i (N— 2w+l) w,
which gives the same value numerically,
but with a different sign, whether m=£N
+ WI-H, or »=JN— m, or for panels
equally distant from the center. Thus
the web members equally distant from
the center and similarly placed with
respect to it, are equally strained by a
uniform load.
MAXIMUM STRESSES IN FRAMED BRIDGES.
77
29. ^It is seen by reference to the meth-
od of deducing eq. (5) that it gives the
maximum shearing force at any panel
for any girder, framed or not, of span
AB, numbered and loaded as AB is in
Fig. 3; hence it applies to the inclined
members of the Pratt, Howe, or triangu-
lar trusses (Figs. 5, 6 and 7) whether the
load (live and dead) is all supposed to
rest on the lower or upper chords, or
both, provided the panel members begin
at the abutment as in Fig. 3.
It is well to note carefully the position
of the front engine that gives maximum
strains on the vertical members of the
Pratt or Howe types. Thus, in Fig. 3,
the shear is the same on the two inclined
web pieces of a particular panel. Now
conceive the struts to become vertical
by moving their tops forward ; the max.
shear they ever sustain is the same as
that of the tie reaching to their top from
the front engine, for the through bridge;
but for a deck bridge this is not so. The
max. strain on a vertical post then ob-
tains when the front engine is directly
over the post; whilst the ties are most
strained when the engine is directly over
the post that connects with their lower
ends (art. 12). For a Howe bridge, the
vertical ties are most strained when
the engine is at their feet for a through
bridge, or at the top of the brace that
connects with their feet for a deck bridge.
The live load must never extend so far
that part of it must be subtracted from
V in finding S (art. 12).
Similarly, the minimum shear a web
piece ever bears (art. 27) is when the
live load extends from the nearest abut-
ment as far as may be without Zw being
increased by any of the live load in the
expression, S=V— Iw (art. 7).
30. The formula does not apply to the
Warren girder, or to Fig. 3, when the
load is on the upper chord (concentrated
at the apices); since the weights are not
then distributed as in Fig. 3.
The methods of arts. 5 and 7 can then
be used.
31. Let us now ascertain the extent of
the error made by assuming that the
load -h panel length either side of an
apex is supposed concentrated at that
apex.
a. Thus in Fig. 3 we vertically con-
sider the £ panel of live load next B as
removed. Except for very short spans
its influence is very slight. In this case
V, and therefore S, would only be in-
creased by it I- j)-j-12 2=174 pounds.
b. We have also disregarded the dead
load J panel next A and B. Including
it, V is increased by J w\ but Sn = V
— 2w is the same as before since 2w is
likewise increased by % w.
c. If the weight of web members is
not supposed concentrated at the apices,
but distributed as it really is, then
Sn = V— 2 iv diminishes in the same
panel the further the section taken
(Fig. 2) is from the abutment; and still
more if any chord piece and load be sup-
posed borne (as it really is) at the apices
of that chord piece.
This case represents exactly the true
solution. Thus in S = V — 2w, the term
2w equals the weights of chords and
loads borne at apices from A to section
taken, + the weight of web to section.
Such refinement is generally unnecessary
for medium spans.
In the triangular truss, shown in Fig.
7, the loads are supposed borne at the
apices of either chord alternately so that
one source of error is eliminated for this
truss. In the Pratt the posts bear one
panel weight of upper chord + part of
their own weight above section taken
over that given by eq. (5), for a through
bridge; whilst for a deck bridge eq. (5)
gives an excess of one panel of lower
chord and weight of post above section
over the true strain. A figure will
illustrate this; also the modification for
the ties of the Howe Truss.
d. In Fig. 3, we have supposed also
the live load on the ^th, or 5th panel in
the Fig., extending up to the middle of
the panel, to be concentrated at the right
apex. Actually part of it is conveyed
by the stringers and floor beams to a
directly. Call P the reaction at a due
to this part. Now V will be larger than
on the former supposition and will be
augmented by a part of P whereas 2w
is increased by the whole of P; there-
fore S=V—2w is less than given by
eq. (5). Eq. (5) is then on the side of
safety.
32. The true value of S can be readily
found, but it is not advisable in practice
to enter into such refinements, for the
supposition of hinged joints, &q. (art. 4)
78
VAN NOSTRAND'S ENGINEERING MAGAZINE.
is never exactly realized in practice;
hence the actual strains in a structure
probably always differ from the com-
puted, especially the components acting
on the fibers most strained; again the
hurtful effects of vibration, oscillation
and impact, modify in an unknown man-
ner the strains due to a statical load,
therefore it seems useless to insist upon
strict accuracy in such statical calcula-
tions.
33. To test further the method of apex
loads: Suppose a uniform load q per foot,
to extend from the apex b, to the right
of a, a distance x to the left from b.
Call a' and b' the parts of this load borne
at the apexes a and b; then we can write
the reaction v at A, due to a' and b' ,
v=ma' + nb',
m and n being certain proper fractions.
The value of S over the 5th panel, due
to the above load, is then, S5= V— a'
= nb/ — (l—m)a/, which is less than nb' .
Now when x<l, b' <iql .:S5<nbf <n%ql.
But if we suppose (as in art. 18) that
the load extends to the middle of the
panel, and that the whole of it, \qi, is
concentrated at b ; S5 would be, n\ql,
which is thus always greater than the
actual shearing force, which we found
above to be less than, n\ql, whether the
uniform load covered the whole or a part
of the panel ab. The supposition is then
on the side of safety.
34. Chord Strains. — The live load as-
sumed has been given in art. 16. Let us
first ascertain how two weights, each:
W= 60000 lbs. and c=50 feet apart, are
to be placed so as to give maximum
strains on any chord panel. Assuming
the notation in Fig. 4, we have,
2W (l-x-jc)
I
Fig. 4
IB
whence the amount at any point B, be-
tween the two weights is,
M=Va—W(a-x)
Now if the two engines can get on the
c / ca\ . . . —^
truss j <1 .*. \a — - I is positive. We
must suppose a<\l, for one-half of the
truss will be subjected to the same maxi-
mum strains as the other half, hence we
need only consider one-half. It follows
that (l — 7~)>1> hence M increases with
x ; so that for x=a, or when the front en-
gine is at the section B, M is a maximum
for that section. When x>a, V is less
than before, and hence M= V'a is less
than for the maximum just found.
f. n-i
A 1 2
35. For a truss, one weight W is on the
same vertical with the apex taken as the
center of moments, corresponding to B of
Fig. 4, the other weight, c=50 feet, from
it on the side of the farthest abutment.
For center chord panels, a + \l .'. M=
fa — — ) W; which is independent of x;
so that the weights, 50 feet apart, can be
placed in any position provided they are
not both on one side of the center panel.
36. Let N=number of panels (12 in
Figs. 5, 6 and 7.
A=height of truss, center to
center of chords.
P= uniform load per panel
=w+p (art. 18).
E, c, I, as defined in art. 18.
fn = strain on wth panel of
lower chord,
MAXIMUM STRESSES IN FRAMED BRIDGES.
79
cn = strain on nth panel of
upper chord,
the chords being numbered as in Figs. 5,
6 mid 7.
It is immaterial whether the loads be
considered as concentrated at upper or
lower apices or both; hence the results
are true whether the trusses are
"through" or "deck." First consider
the effect of the uniform load alone.
For maximum chord strains, the car load
must cover the whole truss, since any
part of it causes an upward moment,
giving compression in the upper chord,
and tension in the lower one.
Conceive the truss cut in two, as per
dotted line, through the panels marked
4 (Figs. 5, 6 and 7) of upper chord, and
the right part of the truss removed, and
apply as in art. 7 forces equal and op-
posed to the resistances of the cut pieces
of the left part. The algebraic sum of
the moments of these forces V, and the
loads about any point must be zero
(art. 5). Suppose the counters (dotted
lines Figs. 5 and 6) removed, if any
should be cut, and take the center of
moments at the intersection of the web
member and either chord to find the
strain on the panel of the other chord
piece cut. The moment of the web
member and chord passing through cen-
ter of moments is thus zero. This is a
general method applicable to any struc-
ture and conduces to simplicity.
Thus if the wth (=4th in the Figures)
panel of the upper chord is cut, take b
as the center of moments, b being the in-
tersection of the web member cut with
lower chord. Then cn A=moment of cn ;
Vnl=moment of V, and (n—\)Y\nl=
moment of the (n — 1) apex loads, P be-
tween A and b, the lower arm of their
resultant being \n\ since they are sym-
metrically disposed with respect to a
point half way between A and b. We
p
have then (art. 5), since V=(N— I) -,
cnh=Vnl-{n-l)Fi?il
= [(N-l)n-(n-
_(N-n)n.
2/t
PI
By giving any value to n, we find cn cor-
responding.
37. Next, suppose section taken across
panel 4=n say of lower chord (Figs. 5
and 6) ; the center of moment is then at
a, vertically above b\ therefore as above
we find
_(N-n)n
fn-~2h~™
the same value as for panel n of upper
chord, as it should be; since V, and the
loads P, have the same lever arms as be-
fore.
The same formulae apply to fig. 7;
only n must have successively the values
1, 3, 5 . . . for the lower chord and 2, 4,
6 . . . for the upper, since the center of
moments for any chord panel is at the
apex opposite on the other chord, thus
giving a uniform strain on two chord
panel lengths in turn, as marked in Fig.
7.
38. Locomotive Excess. — By art. 35
we suppose — placed at a or b (Figs. 5
E
and 6) and — , 50 — c feet to right, to get
u
the chord strains on panels four upper
and lower chords, since a or b is the cen-
ter of moments corresponding to panels
four as marked. The distance from a or
b to A being nl, the reaction at A of E
F
is (art. 19), — [Nl— (nl+c)]; its lever
arm about a or b is nl, so that the mo-
ment on the nth. panel of upper or lower
chord as marked, due to E is,
M= J[NZ-(^+C)]»;=!(N-i -n)nl
For Fig. 7 the same formula holds, as
is easily seen, taking care to give n the
values marked on the chords in turn.
E
Thus - is at b to find max. c4 and at a to
z
find max. t3. The value of cn or tn due
to E is therefore
E
«--
\nl
39. Combining this with the value
previously found due to the uniform
load we have as the maximum strain that
can come on a chord panel, n, as num-
bered in Figs.
5, 6 and 7
@*
x Et .__
T-4
(6)
80
van nostrand's engineering magazine.
40. Example. — As in art. 21, let span
= 200 feet, N=12, 1=-%°-, F=w+p=
14000+16666 = 30666, E=60000 lbs., -
e
= ljand assume the height of truss at
twenty-eight feet.
Eq. (6) becomes then
cn= *„ =[9127(12— rc) + 2976(10j—n»
By making n successively, 1 , 2, 3, 4, 5, 6,
we form the following table: The
second differences are constant, as be-
fore, thus checking the work.
£ = C
A,
A2
c1 =
=M
=(100397-
h28272)l =
128669
104463
V
'V
« ( 91270-
-25296)2"
233132
80257
24206
<v
1 V
' ( 82143-
-22320)3 "
313389
56051
24206
£4'
'V
' ( 73016-
hl9344)4"
369440
31845
24206
V
'V
« ( 63889^
hl6368)5"
401285
7639
24206
V
'V
4 ( 54762H
-13392)6"
408924
—
—
41. The first and second terms in the
( ) are computed by the common differ-
ences, 9127 and 2976.
Thus, in a few minutes time, the
chords are accurately calculated for
their maximum strains. The strains on
the triangular truss Fig. 7 are, as before
explained, for the upper chord c2, c4 and
ce respectively; for the lower chord tl9
tz, th. In Fig. 5 the greatest strain on
any lower chord panel is, tb. In Fig. 6
the greatest strain on any upper chord
panel is c5; the strains on the other half
of the truss being similar to those of the
first half.
The strains thus far found may be
marked on larger drawings than those
given on the corresponding parts. Let
us tabulate the results thus far found in
the following table for truss, Fig. 7. The
length of a diagonal = |/28a + (16-|)a =
32.6; and sec. i=
32.6
~28~'
1.165. Multi-
plying the values S1? S? . . . art. 21, by
1.165 we get the strains on the inch
members given in the column marked
"Strain"; the numeration for the web
members being the same as on Fig. 3, as
given for the corresponding shearing
forces. Thus S, sec. i= strain on end
brace, S3 sec. i for the next brace over
panel 3, Ss sec. i for next brace over
panel 5, S7 sec. i= strain on tie over
sixth panel when it acts as a brace, S8
sec. i= strain on brace over fifth panel
when it acts as a tie, (see art. 24). The
chord strains are designated as in art. 36,
Fig. 7.
Column (d) gives the outer diameter
in inches of the compression member;
column
Q-
tfce ratio of its length to
its diameter; column (th), the thickness
of metal in inches; column (#), the ratio
of the least strain that can ever come
upon a member to the greatest strain that
can ever come on the member; column
(b), the strain for square inch allowed.
The columns headed " Area," " Length,"
"No." give respectively, the area of the
cross section of the member in square
inches, its length and the number of
pieces similarly strained in two trusses.
Column (k) gives the weight of
wrought iron of section one square inch,
and one foot long=J3°- pounds.
The next column gives the " weight "
of member or members in pounds, found
by multiplying together the four previous
columns.
The last column is a summary, giving
the weights on computed strains, in
order, of braces and posts, upper chord,
main and counter ties, and lower chord,
on two trusses.
Column (b) will be explained further
on.
42. Given the " strain," and £=safe
. , „ -. strain
strain per square inch allowed, — 7 —
= area, which is put in " area " column.
The least section of a post allowed was
nine inches, for the vertical posts, that
simply sustain one panel of upper chord
and bracing. The counter brace was
supposed a latticed member. Its total
area is that due to its acting both as a
strut and main tie (6). The counter tie
(8) is supposed enclosed in brace (5).
The main braces and upper chords were
assumed to be " Phoenix columns."
MAXIMUM STRESSES IN FRAMED BRIDGES.
81
Piece.
Brace 1
3
5
*Counter 7
Laticing & Angles
Vertical Posts
Upper Chord c<t
Main Tie 2.
4.
6.
Counter 8 . .
Suspenders.
Lower Chord 1.
3.
5.
30
56
15
th.
81
10
15
10
Strain.
251766
173538
101779
36487
2500
233132
369440
408924
211844
136850
68325
6268
45000
128669
313389
401285
39
5340
4990
3930
3440
280
9050
9270
9270
9900
8700
7500
7500
8470
10420
10420
10420
Area.
47.15
34.8
25.9
10.6
9.
25.76
39.85
44. H
21.4
15.73
9.11
2.
5.3
12.35
30.1
38.51
Len'th
32.6
28.
100
32.6
32.6
32.6
32.6
28.
No.
10
12
Weight.
lbs.
20495
15126
11258
4607
4000
8400
11450
17711
9802
9300
6836
3960
880
5936
5488
13376
17120
Totals.
63886
38963
J6912
35984
* Total area tie 6 and counter 7=9.1-1-10.6=19.7, requiring for a rectaugnlar cross section 3 plates, IS]{GXX> Under
side half latticed bars, 2"x%". Angle irons at -4 corners, 2}4"X'2)4"X%"'
43. Fig. 8 is a section of flooring.
The rails, spikes, chains, &c, are as-
sumed to weigh 42 lbs. per foot. As-
sume the weight of a cubic foot of white
pine timber at 36 lbs.; and the cross ties
1 J feet from center to center. Then the
weight of cross ties and guard timbers
(placed parallel to and on the outside of
the rails) per longitudinal foot is 6X8
(14 + li)f-ftV=124 lbs.
In art. 15, we found the maximum
center live load on the stringers of a 16§'
panel to be 44987 lbs. The dead load of
rails, cross-ties, <fcc. = (42 + 124)-530-. As-
sume that stringers weigh 325 lbs. per
foot. Then the equivalent center load
of one panel of rails, &c, and stringers
is, J491XV-— 4092> making the total
center load on stringer, 490S0 lbs. If we
add 50 per cent, to this to allow for im-
pact, &c, and take 1000 lbs. as the safe
strain for pine, we find that we must
have 6 stringers under the rails of
9|//X20// cross section. The 8 stringers
will thus weigh 365 lbs. per foot of rail.
4 Iron stringers will weigh 300 lbs.
per foot (two under the rails) if their
depth is 26 inches; neglecting the influ-
ence of the web -f" thick, which is about
equivalent to the loss in the rivet holes
in the tension flange. The method of
computation is the same as for the floor
beam.
44. The Floor Beam, also the floor
Vol. XIX.— No. 1—3
6 x S ft- 5 -*
1 ;M i MM M
]6*8 x 14
Floor Beam
1
beam loops sustain a max. live load of
77492 lbs. (art. 15). To this add say
3000 lbs., weight of floor beam, and
531 X-5^—885^ lbs. for stringers, rails,
&c. ; giving a total load, say on the rails
over the floor beam of (77492 + 11850)
= 89342 lbs., or 44671 lbs. on each rail.
The moment at the center is, 44671
(8—21) — 245690 foot lbs. = 2,948,280
inch lbs., which must equal the resisting
moment, fda= 7500X26X15.1, of the I
section (/=safe strain=7500 lbs. per
square inch, c?= 26 = total depth and a=
area of one flange=15.1 square inch).
The cross section, assuming a thickness
of web of y, the depth between flanges
being 24 inches, is 30.2 + 8 = 38.2 square
inch; giving the weight of one floor
beam=38.2x 17£x ^-=2228 lbs. There-
fore 11 floor beams weigh 24500 lbs.
The floor beam loops are put at 5000 lbs.
For such depths of beams (26"), it is
advisable to diminish the depth of girder
from near the center towards the points
82
VAN NOSTKAND'S ENGINEERING MAGAZINE.
of support (see Boiler's " Iron Highway
Bridges," p. 64), both for economy of
beams and loops as» well as for appear-
ance sake. The saving so effected will
be assumed approximately equal to
weight of rivets and stiffeners; which is
sufficiently correct for the purposes of
these estimates.
45. We are now enabled to find the
maximum load on the suspenders of Fig.
7; thus,
Live load on one floor beam 77492 lbs.
Dead load of floor beam 2228 "
Stringers, rails, &c. (300+166)1™ = 7770 "
One panel lower chord, &c 2000 "
89490
Or, say, 45,000 pounds borne by the
suspenders of one panel of one truss.
46. Assuming a wind surface, when
the bridge is covered with cars, 16' high
X 200' long; the intensity of the wind
being taken at 30 pounds per square
foot, the uniform horizontal pressure per
panel is 16 X V" X 30 = 8000 pounds^
w. The trusses are connected between
the chords by bracing similar to that of
the Pratt truss, Fig. 5 at the center;
hence, the sheaving stress, occasioned in
this transverse bracing by the wind
pressure is given by Eq. (5), on making
p and E zero, and w> = 8000. The strain
on any member then, is,
$nsec. i=^(N — 2^ + 1) id sec. i
= 4000 (13 — 2n) sec. i.
Allowing for tension 1500, and for
compression 5000, pounds per square
inch, the rods will average two or three
square inches cross section; and their
total weight, including bolts, nuts, etc.,
is put at 5400 pounds. The cross struts
and portals are assumed to weigh 6000
pounds.
47. It will suffice, for our purposes, to
add twenty per cent, to the computed
material in upper chord and posts for
castings, etc.; and fifteen per cent, to
weight of ties and lower chord for bolts,
nuts, eyes and pins; which allowances I
find given by Mr. O. Shaler Smith in his
" Comparative Analysis of the Fink,
Murphy, Bolman and Triangular Trusses"
Baltimore, 1870.
From the foregoing data we form the
following :
BILL OF MATERIALS.
Triangular Truss— ZW span— 28' high.
Braces and Posts 63866 lbs.
Upper Chord 33693 "
20 per cent, on two last 20570 "
Main Ties and suspenders . . . 26912 "
Lower chord 35984 "
15 per cent, on two last 9434 "
Floor beam loops 5000 "
Lateral Bracing 11400 "
11 Iron floor beams 24500 "
Iron Stringers 60000 "
Rails and Cross Ties 33200 "
Total weight 329849 "
Assumed weight 336000 "
Assumed weight too great by 6151 "
The bridge weight assumed, 336,000
pounds, is, consequently, too great by
6151 pounds.
49. The above allowances for castings,
connections, etc., are intended as avera-
ges common to several trusses that will
be examined. These details are varied
indefinitely by builders. All the steps
have been given, however, to render
adaptation to any particular design easy.
50. In the table, art. 42, we assumed
"^"=13 J" for upper chord. If we put
c?=12 for upper chord and braces, the
total weight of bridge is found to be
6340 lbs. greater than before. If we as-
sume that the increased weight of cast-
ings, rollers, pins, &c, is not over 2000 to
3000 lbs., there is of course economy in
employing the greater diameter; and it
may be found economical to increase it
still further; taking care that a proper
thickness of metal is maintained, say not
less than J inch.
It is hardly necessary to remark that
from the "area" and "d" columns, we
can find the inner diameter d1 and hence
the thickness of metal. Thus j(d2— d*)
=" area," from which d1 is obtained and
-= thickness of metal.
2
The Moose Mine, in Colorado, situ-
ated nearly on the highest point of the
South Park range, is probably the high-
est mine now being worked in the world.
The miners' houses are being built into
the mountain at the mouth of the mine,
considerably over 14,000 feet above the
sea.
SPACE OF FOUR DIMENSIONS.
83
SPACE OF FOUR DIMENSIONS.
Bt Frederick zollxer.
Translated from the German* for Van Xostrand's Magazine.
We shall consider some of the conse-
quences of our theory when applied to
the physical laws of our three-dimen-
sioned phenomenal world. These can be
determined only by conclusions analogi-
cally drawn from those phenomena
which we observe in the projection of
three-dimensioned objects upon a plane.
Suppose that we are observing the
projection of a scalene triangle in the
picture-plane of a camera obscura. If
the plane of the triangle is parallel to the
picture-plane, the area of the projection is
a maximum. If we wish to convert the
projection into its symmetrical opposite,
the triangle must be turned over. Dur-
ing this operation, alterations take place
in all parts of the projection, by which
the area is continuously diminished to a
minimum, which occurs when the trian-
gle is perpendicular to the plane of pro-
jection. With further rotation, the area
increases again to its maximum. A
being endowed with only the conceptions
proper to two-dimensioned space, ob-
serving these changes, would of neces-
sity see a contradiction of the axiom of
the invariability of the actual quantity
of matter contained in a two-dimensioned
object. The projection would appear
larger or smaller without compensation
by any equivalent in the two-dimensional
space. Analogous changes would neces-
sarily be observed in our members, and
in other bodies if they could be convert-
ed into their symmetric opposites. If our
bodies were so organized that we could
at will convert the right hand into the
left, the phenomena of conversion would
consist of a gradual diminution, a mo-
mentary disappearance, and a re- appear-
ance of the hand. All these phenomena
would be miraculous, when considered
from the standpoint of our present space-
perception; since we should see in them
a contradiction of the axiom of the con-
stancy of matter. But this contradiction
vanishes from the standpoint of a higher
conception of, space, when we regard the
* Extract from an article entitled : Ueber Wirkungen in
die Feme ; [ Wisseaschaftliche A bhandlangen von Friedrich
Zollner Leipzig}.
I things of this world as the projections of
substantial objects existing in a space of
I four dimensions. Upon the hypothesis
i that we could, by our will, effect such
transformations of our members, our
feelings would convince us of their essen-
i tially unchanged condition; as now hap-
pens in the case of the varying projec-
1 tions of objects upon our retinae. And
in course of time the intuitive conception
; of a fourth dimension of space would be
developed; as has happened by analc-
: gous process in the case of a third dimen-
sion. In order to comprehend these an-
alogies we must consider that knowledge
of all other corporeal properties, as, for
example, weight and palpability, is ob-
tained through sensations, just as the
knowledge of visible properties is ob-
tained through the eye. Hence the
transference of the projection theory to
the palpable and the heavy introduces no
new principle.
It is well known that the symmetry of
space-forms plays an important part in
crystallography. It often happens that
! in a crystal one-half of the plane-system
I of a simple form is extended by definite
laws in such proportion that the other
half vanishes entirely. Such crystals are
called hemihedric. Both half-surfaces
(called sphenoids) of a rhombic octahe-
i dron have the same relation as an object
to its reflection in a mirror, or as the
right to the left hand. According to the
projection theory to both these different
phenomenal-forms, there is a single cor-
respondent object in four-dimensional
space. The observed difference is a
consequence of a different position of the
object relative to the three-dimensioned
region of projection.
There are bodies which are of equiva-
lence in chemical composition, which ex-
hibit different physical and chemical
; properties. One of the most familiar
examples is tartaric and pyroracemic
acids. The crystals of sodic-ammonic
! pyroracemate agree essentially with those
of sodic-potassic tartrate. But the
former present a remarkable hemihe-
; drism, the octahedric surfaces truncating
84
van nostrand's engineering magazine.
ooly one-half of the edge-system; so
that reckoning from any determinate
truncated surface, such surface appears
at the right in certain crystals, while in
others it appears at the left.
By the addition of sulphuric acid to a
solution of such right hemihedric crystals
right-pyroracemic acid is separated,
which is perfectly identical with tartaric
acid and which gives no precipitate with
a solution of sulphate of lime. A solu-
tion of this right pyroracemic turns a
perpendicular polarized ray of light to
the right. The acid obtained from a so-
lution of left-hemihedric crystals by a
like process gives the same reaction as
tartaric acid, and gives no precipitate
with sulphate of lime, but is optically
left-handed. If the right and left
acid are mixed in solution, the mixture
gives no circular polarization, but throws
down a precipitate with sulphate of lime.
The crystals of tartaric acid and of right-
pyroracemic acid are hemihedric but of
direction opposite to that of crystals of
left-pyroracemic acid.
These facts furnish an interesting ex-
ample of the connection of a space-dif-
ference in crystals directly apprehended,
with one that is indirectly apprehended
by means of chemical and optical appli-
ances which demonstrate a difference in
the arrangement of the atoms constitut-
ing the bodies. In the latter case there
results a presentation to our organism of
a difference in quality of matter, similar
to the qualitative differences in tone and
color which are due to the different
lengths of the waves of sound and light.
In a space of four dimensions the
right and left hemihedric crystals
would appear as species of one and
the same object; so would the chemical
difference resulting from the molecular
grouping of atoms. The change of one
crystal form to another, and of one chemi-
cal property to another, could be effected
by changing the relative position of the
four-dimensioned objects; just as we can
see the writing on a transparent sheet
of paper transformed into its symmetric
opposite by looking at it from the oppo-
site side. If there were beings who
could, by act of will, transform in a
space of four dimensions a substance
apprehended by us only indirectly by
means of its three-dimensioned pro-
jection, so that the space-configuration
of its atoms should be changed to the-
symmetric-opposite, the phenomenon
would seem miraculous. For the tartaric
acid crystals would seem to be converted
into crystals of right-pyroracemic acid,
not only in respect to external form,
but also in respect to chemical constitu-
tion. If we had a four-dimensioned body
subject to our will, we should be able to
interchange the crystals into various
dispositions whose differences would in-
volve some space-meaning; just as hap-
pens in the case of differing projections
and operations on a three-dimensioned
body effected from different standpoints.
If we explain this process of conver-
sion in the symmetric disposition of
atoms by attributing them to moving
forces, then these must operate in di-
rections which fall in the fourth dimen-
sion; that is, in a direction perpendicular
to the three-dimensioned region of pro-
jection which constitutes our present
space. This direction would be repre-
sented by a complex space co-ordinate,
such as has been employed by Gauss in
the interpretation of the imaginary
quantity in regions of less manifoldness.
If we regard the distance between two
atoms and the intensity of their reactions
in our three-dimensional space as the
projections of similar magnitudes from
a space of four dimensions; then they
can alter in magnitude and form and
store of potential and kinetic energy of
the three-dimensioned projection (our
material object) only by altered position
relations in the four-dimensioned object.
Hence, the axiom of the conservation
of a constant amount of ' energy holds
completely in a space of four dimensions;
in fact, it is the premiss, upon which de-
pends the transfer of enlarged concep-
tions of space to physical processes.
To illustrate : suppose a number of
congruent triangles cut from paper to be
let fall from a height upon a table.
These triangles, which, in a space of
three dimensions, would represent iden-
tical two-dimensioned crystals, revolve as
they fall, and, finally, come to rest upon
the table in random positions. Regard-
ing the tangent-plane of the triangles,
and the table as the region of two-di-
mensioned beings, it is obvious, that
these beings would recognize among
these triangles symmetric but incongru-
ent forms, analogous to our hemihedric
SPACE OF FOUR DIMENSIONS.
85
crystals. During the process of rotation,
the triangles would, for a time, disappear
from sensible space.
With respect to this connection be-
tween the chemical properties and the
space-relations of the atoms of a body, it
is a significant fact, that attention has
lately been directed to the meaning of
s-pace-moments in the domain of chemis-
try. In the year 1835, a short memoir
was published at Rotterdam, with the
title "La Chimie clems Espace, by J. H.
Yan't Hoff, with an introduction by J.
"VNTislicenus, Professor of Chemistry at
the University of Wiirzburg. The lat-
ter, speaking of the aim and import of
this memoir, says : "That the atoms
which are assumed to constitute a mole-
cule must be arranged in some definite
space-configuration, and that the same
elementary atoms with the same order of
succession in their respective composi-
tion in complex molecules, may be spa-
tially grouped in different ways, so as to
give to structurally identical molecules
slight differences in properties, has long
been conjectured; and there have been
peculiar phenomena which required some
such explanation as that which is here
indicated. I myself, in my investigations
upon Paralactic acid, expressed the
opinion that the facts compelled an ex-
planation of the difference of isomeric
molecules of the same formula by re-
ferring it to the different position of the
atoms in space; and that geometric con-
ceptions of the composition of the mole-
cule, must be introduced into chemical
theory."
" The fundamental idea of Yan't Hoff's
theory, lies in the proof that combina-
tions of an atom of carbon with four
different simple or compound radicals
must always furnish two cases of spatial
isomerism."
Again he says : a A simple consider-
ation shows the inadequacy of our so-
called modern structural formulas. They
represent the molecule, which is of three
dimensions, as planar. The discrepancy
with the fact involved in this assumption
is obvious; and a reform of the preva-
lent views is to be desired."
" In the case in which the four affini-
ties of a carbon-atom are satisfied by
\ four different groups, our theory leads to
! a construction of two and only two
1 tetrahedrons, which are incapable of
! superposition; one of which is the image
: of the other, and which may be called
j enantiomorphic forms."
The above quotation illustrates the
j truth of Riemann's assertion that oppo-
sitions of thought and of the facts of ob-
servation are the conditions by which
our knowledge of the world advances.
The need and the impulse to push for-
ward the lines of knowledge are always
measured by the violence of the para-
doxes which we encounter in our ex-
perience.
DESCRIPTION OF THE AUBOIS CANAL LOCK, SITUATED ON
THE LATERAL CANAL OF THE LOIRE RIYER.
By Prof. WILLIAM WATSON, Ph. D., late U. S. Commissioner.
method of emptying and filling the
lock by the process invented by
the marquis of caligny, viz., by
means of oscillating liquid col-
umns; time to fill or empty the
lock; amount of water saved by
this process; cost.
Process Invented by the Marquis of
Caligny. — We know that for each pass-
age through a lock, whether up or down,
a quantity of water must be drawn from
the upper bay to fill up the lock a height
• equal to the difference of level between
the two bays; this height being called
the lift of the lock, and the volume of
water required for this purpose, the prism
of lift. The system invented by the
Marquis of Caligny and applied to the
Aubois lock, has for its object to dimin-
ish this waste by causing water from
the lower bay to ascend into the lock-
chamber when the latter is to be filled;
and also by making part of the water in
the lock-chamber ascend to the fore-bay
when the lock-chamber is to be emptied.
The system is founded on the known
VAN NOSTKAKD'S ENGINEERING MAGAZINE.
properties of oscillating liquids, which
will presently be explained.
The work consists
1st. (Figs. 1, 2,) of a full-centered
aqueduct, a b d, 1.20 meters wide, 1.55
meters high under the keystone, and
having its bed on a level with the bot-
tom of the lower bay; the depth of the
latter being 1.80 meters, the intrados of
the keystone is 0.25 meter below the
level of the lower bay. This aqueduct,
which is semicircular between the two
heads, empties into the lower gate-cham-
ber, I, by an enlarged opening, (Fig. 6,)
and on the upper side it connects with
two separate reservoirs, X and Y, (Fig.
1) situated behind the upper gate-cham-
ber.
2d. Of a discharging-channel or sav-
ing-basin, i s t, connecting the reservoir
Y with the lower bay by a sluice, (c) ;
the other reservoir X communicates with
the upper bay.
3d. Of two vertical movable pipes,
q, r, open at both ends, and resting upon
two circular openings made in the walls
of the aqueduct. One of these pipes is
placed in the reservoir communicating
with the upper bay, and the other in the
one communicating with the lower bay.
Both pipes rise 0.10 meter above the
level of the upper bay; the lower-bay
pipe, r, is 1.48 meters in diameter and
3.57 meters high, the upper bay pipe, q,
is 1.40 meters in diameter and 2.97
meters high. When these pipes are
lowered upon their seats, the upper ex-
tremity of the aqueduct is shut. If we
raise the upper pipe, q, the water from
the upper bay enters the aqueduct; if,
on the contrary, we raise the lower pipe,
r, the water from the lock goes into the
THE AUBOIS CANAL LOCK.
Explanation. — Fig. 1 represents the lock at Aubois on the lateral canal of the Loire
River, i s tis the saving basin ; a b d the underground aqueduct ; k I the lock ; k the upper,
and / the lower gate-chamber.
Fig. 2. The longitudinal section e q r of the two reservoirs X and Y, and that of the
aqueduct a b d with the lifting pipes q and r.
Figs. 3 and 4. Sections of the reservoirs X and Y made by the planes o p and m n.
Fig. 5. Section of the aqueduct.
Fig. 6. Section of the aqueduct at /, where it discharges into the lower gate-chamber. .
Fig. 7. Transverse section of the saving basin.
DESCRIPTION" OF THE ATTBOIS CANAL-LOCK.
87
saving-basin* or vice versa, according to
their respective levels.
The manner of working is as follows :
Suppose the full lock is to be emptied;
we raise the pipe r, the water from the
lock-chamber passes through the aque-
duct under the pipe, and enters the sav-
ing-basin, which is supposed to be on a
level with the lower bay. After having
held the pipe r raised during a few sec-
onds for the water to acquire its velocity,
we drop it back upon its seat; the water
in the aqueduct, having no issue under
the pipe r, rises in the interior of both r
and q, and pours over their tops into the
reservoir X, and connected with the upper
bay. Thus, on account of the living
force of the moving liquid mass in the
aqueduct, a part of the water is carried
into the upper bay. When this first os-
cillation has ceased to cause the water to
overflow from the pipes q and r, we re-
commence the same operation by raising
again the pipe r; a new column of water
issues from the lock; we interrupt again
its flow under r, and a new oscillation
produces a new overflow into the upper
bay. As this operation is repeated the
lock is emptied, cne portion into the sav-
ing-basin and thence into the lower bay,
another portion into the upper bay. As
the difference of level which causes the
oscillation diminishes, the height of the
oscillation, its duration, and the amount
of overflow at each new opening, dimin-
ish also; hence, after a time the oscilla-
tions becjome insignificant, as also the
water saved by them; at this time we
may complete the emptying by opening
continuously the pipe r; but we may also
operate otherwise and produce a new
saving. For this purpose we shut the
sluice-gate, c, between the saving-basin
and the lower bay, and raise the pipe r;
a great oscillation occurs, which causes
the water to rise in the saving-basin
above the level of the lower bay and to
fall in the lock below this level; on low-
ering r at the end of this great oscilla-
tion we shut into the saving basin a layer
of water which will serve for filling the
lock, and we have at the same time
caused a difference of level between the
lock and the lower bay sufficient to make
the lower lock-gates open spontaneously.
The layer of water obtained at Aubois
by this final oscillation is 0.15 meter thick.
If it is required to fill the lock we
commence by employing the layer of
water stored in the saving basin. For
this purpose we raise the pipe r, and the
water being higher in the basin than in
the lock, it enters the latter, producing
thereby an oscillation, which causes the
level in the lock to be above that in the
basin, and loicer in the latter than in the
lower bay, so that this first volume in-
troduced into the lock comprises, not
only that which has been raised by the
previous emptying, but also another por-
tion taken from the saving-basin, i.e.,
from the lower bay. At the end of this
initial oscillation we let fall the pipe r,
open the sluice c, and proceed in another
manner. We raise the pipe q y the
water from the upper bay enters the lock
through the aqueduct; at the end of
several seconds it has acquired its veloc-
ity, then we let fall the pipe (7 and at the
same instant raise the pipe r y the water
in motion in the aqueduct then produces
the effect known as aspiration upon the
water of the saving-basin, which has
already been put in communication with
the lower bay, and draws it by an oscilla-
tion into the lock; §yo that the volume
introduced by this last operation consists
of two portions, the first portion being
taken from the upper bay to generate
the velocity, and the second from the
lower bay by utilizing this velocity. At
the end of the oscillation we let fall the
pipe r, raise the pipe q, and a new
oscillation brings into the lock a new
volume; we continue this operation until
the diminution of the difference of level
between the upper bay and the lock
causes the oscillations to become insig-
nificant; from this moment we keep the
pipe q raised, and thus finish the filling.
This prolonged opening produces a final
oscillation, by which the water rises in
the lock higher than in the upper bay,
and opens spontaneously the upper lock-
gates.
This canal-lock has been in operation
since 1868, and we find
1st. That seven or eight oscillations
suffice to fill or empty the lock in five or
six minutes.
2d. That for filling the lock without
using the reserve in saving-basin, the
volume of water taken from the lower
bay is 0.41 V, V being the prism of lift,
so that the saving by this operation is
about two -fifths of V.
88
VAN NOSTRAND'S ENGINEERING MAGAZINE.
3d. That during the process of empty-
ing, the volume sent into the upper bay
is about 0.386 V, without considering
what is saved by the final oscillation.
The sum of the volumes raised by the
two operations is (0.41+0.386) V=0.796
V. By utilizing the great final oscilla-
tions the saving amounts to 0.90 V.
This system of lock, while it econo-
mizes the water used, produces neither
lowering in short bays, nor exaggerated
velocities in the narrow passages; and
constitutes an ingenious use of the prop-
erties of liquids in motion. Its applica-
tion to the Aubois lock cost about 40,000
francs, but much of this was owing to
the difficulties of position and the nature
of the soil which required special
precautions. A considerable economy
might be made by placing the aqueduct
along the side-walls of the lock.
REPORTS OF ENGINEERING SOCIETIES,
American Society of Civil Engineers.—
The annual Convention, beginning June
18th, at Boston, will discuss topics upon which
papers hive been presented during the year.
In addition to these, it is expected that the
following subjects will be presented by papers
printed previous to the date of the Convention,
or read at its meeting :
Dams across Water Courses. William J.
McAlpine.
The rain fall during a storm in October,
1869. James B. Francis.
The law of Tidal Currents. J. H. Striedinger.
The South Pass Jetties ; descriptive and in-
cidental notes and memoranda. E. L. Corthell.
Discussion on the preceding paper. Charles
W. Howell.
Reminiscences and experiences of early en-
gineering operations on railroads, with especial
reference to steep inclines. No. 1, W. Milnor
Roberts. No. 2, William J. McAlpine.
Resistances on Railway Curves. S. Whinery.
Notes on the papers in reference to Incline
Planes and Resistances on Railway Curves. —
Octave Chanute.
Agricultural Drainage. Ed. N. Kirk Talcott.
A graphic method of representing railroad
accounts. Charles Latimer.
Science, old and new. Its relation to Engi-
neering. W. Milnor Roberts.
The Mississippi River. — B. M. Harrod.
Brick Arches for Large Sewers. R. Hering.
Improvement of Galveston Harbor (2d
Paper). Charles W. Howell.
The Flow of Water in Pipes. Charles G.
Darrach.
The proper arrangement and ventilation of
house drains. Charles E. Fowler.
On a newly discovered relation between the
tenacity of metals and their resistance to tor-
sion. R. H. Thurston.
On Gauging Streams. Clemens Herschel.
meeting of the american *lnstitute of
Mining Engineers at Chattanooga. —
The business proceedings of the Convention at
the first session held on the 22d, consisted of an
address by Dr. Sterry Hunt, and the reading of
the papers by J. E. Sweet M. E. , and R. W.
Raymond of the Engineering and Mining
Journal.
In the afternoon of the same day the Insti-
tute visited the works of the Roane Iron Co.,
the Tennessee Iron & Steel Co., the Chattanooga
Iron Co., and the Vulcan Iron and Nail Works:
the party then ascended Lookout Mountain.
The programme for the remainder of the
week included for Thursday, a trip by steamer
to Shellman, a visit to the Dade Coal Mines ;
return and visit South Pittsburgh, Victoria,
ets., and evening session*at Chattanooga.
Friday : In Alabama and Georgia iron and
coal fields.
Saturday : Return to Chattanooga, and in
evening leave for Rockwood.
Sunday : At Rockwood, afterwards return-
ing to Chattanooga or leaving for home.
Engineers' Club of Philadelphia. — At a
recent meeting of the Club, Mr. Wm. F.
Sellers read an interesting paper on the Ken-
tucky River Bridge. The paper was illustrated
by large photographs of the structure and by
working drawings. The Cincinnati Southern
Railway crosses the Kentucky River at a point
where several years ago, four stone towers
wTere erected by Mr. Roebling. The structure
for which these were intended was never com-
pleted. The river at this point is about 300
feet wTide, and flows in the bottom of a narrow
canon, about 300 feet deep and 1,300 feet wide.
For numerous reasons, a pier in the river was
rendered impracticable; so it was decided to
use three spans of p75 feet each. These were
erected without the use of any false works,
which the great height of the bridge, and the
swift current of the stream precluded. Though
a continuous girder in three spans would have
fulfilled all of the conditions necessary during
erection, yet the fact that the iron piers would
vary in height with the temperature while the
cliff abutments would not, made it obligatory
thar the spans should be so hinged as to permit
of this vertical motion of the piers without
altering the strains in the truss. It was finally
decided to construct the bridge with a central
span which may be described as a beam sup-
poried near each end, the overhanging portions
helping to support the central portion, the
piers acting as fulcrums.
The end spans were supported at the shore
ends by abutments, and at the other end by the
weight of the middle span acting over the
piers as levers; the distance from the pier to
the contraflexure point being the short arm of
the lever. This important point was found by
dealing with the truss, panel by panel, and
member by member. The truss is 37^ feet
deep, 18 feet wide and each span divided into
20 panels of 18| feet each. All connections
between the ties, posts and cords, were made
by pins. Those pins which were strained in
erection were forced in place by hydraulic
pressure and served as rivets, wThile other pino
REPORTS OF ENGINEERING SOCIETIES.
89
were put in loosely. The dimensions of piers
and masonry, and the results of the final tests
were given, all proving of very great interest.
Dr. Wm. D. Marks called the attention of
the Club to some new and interesting drawing
instruments.
One of the instruments was of Prof. Mark's
own design, being an adaptation of the Mar-
quois rule which enables a draughtsman to
shade a cylinder, shaft, &c, with mathematical
correctness.
At the last meeting of the Club, Mr. Henry
G. Morris made some very interesting remarks
in regard to the proposition which Messrs.
William Cramp & Sons have made to the Phil
adelphia Water Department. They propose to
furnish steam pumping machinery and founda-
tions, boilers and air vessel complete, with all
valves and attachments, inside the house, to
the pumping mains proposed to connect with
the distributing pipes of the Belmont Water
Works, on the east side of the Schuylkill river,
and operate the same.
They also propose to furnish all coal, stores
and supplies, provide attendants and maintain
repairs free of all charges to the city in the first
cost and operating expenses, for the same sum
per million of gallons pumped, as it now costs
at the Belmont Works, that being the lowest
cost, in the list for steam pumpage.
At the expiration of five years from the time
the machiuery is started, it shall become the
property of the City of Philadelphia without
further cost or expense : ground and houses
to be furnished by the City and located at the
Schuylkill Works, the Department to so ar-
range its pipes that any excess of pumpage not
required on the East side can flow into the Bel-
mont Basin, in order that continuous pumpage
can be maintained. The machinery to be capa-
ble of pumping fourteen millions of gallons per
twenty-four hours, the quantity of water
pumped to be determined by the method now
used by the Department, and payments to be
made quarterly on quantities certified by the
Chief of the Department.
The * ost at the Belmont Works, the cheapest
of anv of the works in the City, for pumping
1,000 000 gallons 200 feet high, was, in 1877,
$14.12. The Messrs. Cramp have stated that
they are satisfied that by using their own en-
gines, they can supply the 14,000,000 gallons
every twenty-four hours at the same rate as
now done at the Belmont Works, $ 14. 12 and
still make a good profit.
Mr. Morris gave an estimate of the cost at
which the work could be done, and by com-
parison with the duty of the Lowell engines
showed approximately what profits might be
expected. At Lowell, Mass., the cost was, in
1877, $10.71 per million gallons, for raising
water into Reservoir, a height of 166 feet with
the Morris engine.
Gen'l. Herman Haupt made very interesting
remarks in regard to the Seaboard Pipe Line.
About two years ago the Penna Transportation
Company called upon General Haupt for esti-
mates in regard to cost of transporting oil to
the seaboard by means of pipes. The first
pipes in the oil regions for the transportation of
oil were laid fourteen or fifteen years ago. At
present there are some 2,000 miles of pipe in
operation between the wTells and the railroads.
At first the Pipe line Co's. met with a very
determined opposition from the teamsters and
boatmen, but after waging a bitter \* ar against
the new system they had to succumb, and pipe
lines became the only mode for conveying oil
from place to place. The Legislature passed
an Act allowing pipe lines in four or five of
the Western counties. The Conduit line was
started to operate between the oil regions and
Pittsburg. After a sharp contest with the
Pennsylvania Railroad it succeeded in getting
across the line of the railroad by using a public
road. The oil was received in tanks which
were mounted on wheels, hauled across the
railroad, pointed into receivers, and went on
its way to Pittsburg. Even with this extra ex-
pense of handling the line paid well
Upon visiting the oil regions it was found
impossible to get satisfactory data for formu-
lating the hydraulic pressure and making
necessary calculations for an estimate of cost
for a loner line. The seaboard line propose to
use a six-inch pipe which will give a capacity
of 6,000 barrels discharge per day, the line will
be tested to 1800 pounds pressure per square
inch, and worked at 400 pounds per square
inch. Preliminary surveys have already been
made. The first station will be located at
Parker City, from wdiich the oil will be forced
a distance of thirty-five miles : the second
pump will force it twenty-six miles further :
the third pump seventy miles further : and the
last pump which will be located on the West
side of Tuscarora Mountain will send it to Bal-
timore a distance of 102 miles. The pressure
at each station will be 400 pounds, equal to a
head of 1200 feet of oil. Distances between
stations varying with the profile of the ground
crossed.
The estimated cost of transportation is one
cent per barrel at each pump, the distance be-
tween pumps being immaterial. Five cents
per barrel is a full estimate of cost for trans-
portation from the oil regions to the seaboard.
A six-inch line of pipe can be made at a cost of
$ 8,000 per mile, making the total cost of the
projected line $ 1,750,000. Construction of the
seaboard line will be commenced in two or
three works.
One of the most important points in the con-
struction of pipe lines is to allow for contrac-
tion and expansion due to changes of tempera-
ture.
A pipe line is certainly the most economical
and natural method for transporting fluids, and
there is no more reason why oil transported in
pipes should be exported than when transport-
ed in cars.
After transaction of business the Club ad-
journed, to meet October 5th, 1878.
INSTITUTION OF MECHANICAL ENGINEERS.—
The second meeting of the members of this
Institution was held recently at the Institution
of Civil Engineers, Great George Street, West-
minster. Mr. Boyd read his paper on "Ex-
periments relative to Steel Boilers." Various
test experiments on marine steel boilers were
described in this paper, and the conclusions de-
90
VAN NOSTRANITS ENGINEERING MAGAZINE.
duced were that (1) steel plates can now be ob-
tained in which absolute practical uniformity
can be relied on, extending over a large quanti-
ty of material ; (2) that the material is serious-
ly injured or crippled to the extent of some-
thing like 33 % by punching, if the clearance
given between the punch and the die be about
Y^th inch, which is usual in good boiler-mak-
ing work; (3) the injury or crippling of the
material does not amount to any appreciable
quantity if the holes are drilled; (4) the nature
or quality of the material is practically restored
entirely if the plates are properly annealed; (5)
that it is desirable that all holes in the con- !
struction of a steel boiler should be drilled [
rather than punched; and (6)' that, owing to j
the early tendency to buckle in steel plates, j
special care is necessary in staying flat sur- j
faces, especially where the plates are thin.
Dr. Siemens said the first news he had of this
application of the LandoTe steel was unfortu- 1
nate, for the steel had entirely failed to stand s
the test. Mr. Boyd had now stated the circum- j
stances under which this apparent failure
arose. A test plate had been fastened between
two bars of iron, and when the tensile strength
was applied, the steel, instead of elongating 20
or 25 per cent., as was expected, and then
breaking across the rivets, broke through the
fastening along a line of fracture. 30 or 35 per
cent, longer than the fracture of least resist-
ance. He suggested that the cause of failure
would probably be found to lie in the mode in
which the fastening had been made. Mild steel
yielded very much before rupture of the tensile
strain was applied fairly over the whole section,
and this made it necessary that it should be
fastened along the whole line of its section. In
the particular fastening referred so, two large
rivets show forward, and naturally would tale
nearly the whole of the strain, while the other
four rivets stood back to such an extent, that
before they would receive any considerable
portion of the strain, the two forward rivets
would be loaded to such an extent as to cause
a partial yielding of the metal, and, being near
the edge, tearing action would set in. Many
people advocated the use of iron rivets for
riveting mild steel plates, but he could not too
strongly argue against that practice. It was
utterly against nature to stretch material like
mild steel, together with iron, which behaved
quite differently as to elongation and yielding-
faculty. He was glad to see Mr. Boyd had
adopted steel rivets. He did not agree that
punching necessarily diminished the strength
of a steel plate something like thirty-three per !
cent. He found by experiment that in squar- j
ing a punched hole the strength of the metal ]
was entirely restored, showing that the cause |
of weakness was in the immediate vicinity of
the hole, and did not extend any depth inio
the metal. The addition of nuts to the stays
showed a remarkable increase of strength, and
he hoped that mi de of staying would be
adopted. It was a question whether for flat
stay plates this very mild steel should be used;
it would probably be more advantageous to use
steel containing, perhaps, T4oths of carbon. He
had lately witnessed some experiments at
Swindon with a view of bursting a steel^
boiler. The results showed that it was impossi-
ble to do so, the boiler might swell and be
racked at the joints so as to produce leakage,
but that would prevent any further accumula-
tion of pressure.
IRON AND STEEL NOTES.
Preservation of Iron. — The process of pre-
serving iron by means of a coating of its
own oxide, recently introduced by Professor
Barff , is one which gives such excellent results
that we are somewhat surprised at having
heard little or nothing of it since its discussion
at more than one scientific meeting. There
are other workers, too, in the same direction,
one of whom, Mr. George Bower, of St. Neots,
has shown us a number of specimens of his
work. These yield nothing in appearance to
the samples of Professor Barff, and their pro-
tective coating is fully equal in efficiency, since
it is identical in chemical composition. The
process by which they are prepared is the out-
come of a most elaborate and costly series of
experiments, which have been carried out at
Mr. Bower's works in St. Neots. It may be
explained in a few words to consist in exposing
the iron at a suitably elevated temperature to
the action of the oxygen of the air. This
action forms a coating of the oxide known to
chemists as magnetic oxide of iron, which is in-
capable of change under any ordinary condi-
tions, and which forms on the surface a harder
and more coherent film than can be obtained
by any other means. Professor Baiff, as our
readers know, utilized the well-known fact of
steam being decomposed in presence of red hot
iron; hydrogen being set free and a coating of
magnetic oxide of iron formed on the surface
of the iron, thus: Fe3+4H20=Fe304-f 4H3.
It has not, however, been generally known that
free oxygen, as it exists in the atmosphere, is
also capable of coating under suitable condi-
tions, the surface of the iron with the same
oxide as that yielded by steam. To Mr.
Bower is due the credit not only of satisfac-
torily eliciting this important fact, Jjut also of
its industrial application. The advantages that
air must possess over steam are almost too
obvious to require enumeration, and 'from an
economical point of view alone the process
deserves every encouragement.
The coating given by the use of air, although
permanent and lasting, is of peculiar bt auty,
and of a greyish or neutral tint, so that for
many purposes the necessity of further orna-
mentation by painting, &c, is dispensed with.
The coating has been tested under the severest
conditions, and has always resisted most com-
pletely all attempts to set up rusting. It
should also be mentioned that although the
iron may rust at spots from which the magnetic
oxide has been removed, the rusting is con-
fined to those spots, the lateral rusting which
makes the use of paints, &c, objectionable,
not taking place to even the slightest extent.
The method adopted in carrying out this
process is to place the articles in a chamber,
which is capable of being completely closed,
and gradually raise the temperature to the
KAIL WAY NOTES.
91
requisite degree, ranging between a dull and a
bright red heat, according to the ultimate use
to which the articles may be applied. Air is
then passed in, and the chamber completely
closed for one^hour, when the inlet and outlet
pipes are again opened and a fresn supply of
air sent into the chamber, which is again
closed. This renewal of the air at the end of
every hour is continued until the required
thicknesses of magnetic oxide is formed on the
iron. The air is supplied from a gasholder, or
else by connecting the outlet pipe with the
draught of the chimney shaft in connection
with the furnace heating the chamber. The
process is found to answer particularly well
for cast iron, but with a slight modification,
which is now being worked out, it answers
equally well for every other description of the
metal. — Iron.
The Pig Iron Production of the United
States. — Statistics have been published
by the American Iron and Steel Association,
from which it appears that the grand total for
1877 was 2,314,585 tons of two thousand
pounds, against 2,093,236 tons in 1876, a gain
of 221,349 tons. Twenty-two States made pig
iron in 1877. As compared with other years
immediately before and since the panic, the
production of 1877 shows a decided reaction
from extreme depression, but still falls far
short of the country's best achievements. The ;
figures are as follows :— 1872, 2,854,558 net j
tons ; 1873, 2,868,278 tons ; 1874, 2,689,413
tons ; 1875, 2,266,581 tons ; 1876, 2,093,236 \
tons ; 1877, 2,314,585 tons. The production
in 1877 was about 50,000 tons greater than in
1875. The year 1876, the Centennial year, was j
the year of greatest depression, and 1873 was I
the year of greatest production. Of the total |
production of pig iron in 1877, 1,061,945 net
tons were bituminous coal and coke, 934,797 I
tons were anthracite, and 317,813 tons were I
charcoal. In 1873, the year of greatest pro- |
duction, the proportions were as follows :
Anthracite, 1,312,754 net tons ; bituminous !
coal and coke, 977,904 tons ; charcoal, 577,620 |
tons. It will be seen that, while the produc- j
tion of anthracite and charcoal pig iron has !
largely fallen off, that of bituminous coal and
coke pig iron has very materially increased, i
The whole number of furnaces in the United I
States which were completed and either in
blast or ready to be put in blast at the close of
1877 was 716, against 712 at the close of 1876.
Of the furnaces completed at the close of 1876,
236, or less than one-third, were then in blast,
and 476 were out of blast. At the close of 1877
there were 270 in blast and 446 out of blast,
showing an increase in that year as compared
with 1876 of thirty -four active furnaces.
RAILWAY NOTES.
Some time ago reference was made in this
column to a statement of the chairman of
the East India Railway Company, that the
average mileage of their engines during the
previous half year was 1250 miles per month,
which he believed exceeded that of any other
railway in the world. This the Railway Age
retorted was not at all an extraordinary mile-
age, citing among others the case of an engine
on the Atlantic and Great Western Road,
which made in one month 3681 miles. A cor-
respondent of that journal, and master me-
chanic of the Cleveland, Tuscaroras Valley
and Wheeling Road, writing recently, says:
''Passenger engine No. 11 on this road in 1877
made 51,395 miles, making in one month 5640
miles, and engine No. 10 made 48,125 miles,
both in passenger service. The first cost 11.26
cents and the second 11.70 cents per mile run.
I think that perhaps this is among the greatest
mileage made by engines in one year." This
is considered a remarkable record, the first en-
gine making an average during the entire year
of 165 miles per day, excluding Sundays, and
in one month averaging 216 miles per day,
counting twenty-six working days to the
month. — Engineer.
A paper was lately read before the United
Service Institution by Mr. J. L. Haddan,
C.E., on "Pioneer and Military Railways.*' A
section of a military post and rail or pioneer
railway was built on the ground lying waste at
the rear of Whitehall Place, to show the sim-
plicity of the work, its constructors being ten
soldiers from the Grenadier Guards and two
laborers. The railway was primarily designed
by the author of the paper to meet the need in
the East of a speedily constructed, cheap and
effective means of transport for men and stores
over a wild country without the necessity of
surveying, leveling and passing through the
preliminary stages of ordinary railway making.
The section built recently in the grounds of
Whitehall is a "one central rail" structure with
two light side guide rails, the line running
upon seven feet posts, 440 to the mile, the roll-
ing stock upon it being designed upon the
" camel saddle " principle. The carriages and
eDgines fall on each side like panniers on an
animal's back, the wheels of the engines,
trucks, and carriages being horizontal and
gripping the guide rails. The material of the
railway is wholl}' of timbers brought on the
ground ready cut for use, and the plans having
been explained to the sergeants of the fatigue
party, the piles were sunk in the ground, the
cross timbers fixed and bolted, and by a series
of wedges an 80 feet or 100 feet section of the
line, running over very uneven ground, is made
secure, the wedges taking up any slack in the
struts. In the discussion which followed the
reading cf the paper, Sir Garnet Wolseley
speaking of the railway in the Crimea, said
that "though that was not a great success, it
was very useful, and by making it the English
nation was the first to use railways in war.
The great thing in regard to railways used in
war was that they should be quickly made and
worked, for time was everything. If Ave
had to go to war and to operate inland in a
country where there were no roads, it would
be of the greatest importance to have a line
from the base of the scene of operations; and
Mr. Haddan's proposals gave a system which
would meet the requirements of an army in
that position. As to particular railways which
had been proposed for army transports, in these
92
VAN NOSTRAND'S ENGINEERING MAGAZINE.
days of short and sharp campaigns, earthworks
were out of the question, for now armies did
not sit down to long campaigns like the sieges
of Toy and Sebastopol. Other systems re-
quired good roads, but for a country without
the roads, and in rapidity and simplicity of
construction, Mr. Haddan's railway would
meet an army's wants." — —
ON the Continent the adoption of steam tram-
way engines instead of horses is becoming
very general. Rouen, Cassell, Barcelona,
Bilbao, Lisbon, Oporto, the Hague, and other
important towns are all following the example
set by Paris, which has working in its streets,
engines which are noiseless, smokeless, and
free from any objectionable features calculated
to obstruct or in any way interfere with the
ordinary traffic. As shown in the reports of
tramway companies and the remarks of the
chairmen at the annual meetings, the proprie-
tors are fully alive to the importance of the
subject, and are strongly inclined to take the
necessary steps to replace horses by mechanical
power. But as public opinion had to be edu-
cated in the first instance as regards the tram-
way itseif, so also must it be enlightened re-
specting the traction; meantime, nothing will
be gained by forcing legislation. No one
doubts that the use of steam traction in the
streets is not remote, but there is no question
that before introducing it into the metropolis,
provincial towns, and country districts waiting
to be thus opened up, offer, in the first instance,
the widest and most encouraging scope for its
application. As feeders to existing railway
lines, and as branches connecting agricultural
areas with the centers of commerce from
which they are at present excluded, steam-
worked tramways will be a most important and
industrial aid. — Engineering.
ENGINEERING STRUCTURES.
Long Span Railway Bridges.— At the meet-
ing of the Institution of Civil Engineers,
held on Tuesday, the 21st of May, the paper
read was on " The Design generally of Iron
Bridges of very large Spans for Railway
Traffic," by Mr. T. C. Clarke, M. Inst. C.E.,
of Philadelphia.
Since the year 1863, when a paper on the
subject was presented by the late Mr. Zerah
Colburn, no communication had been sub-
mitted to the Institution relative to the con-
struction of iron railway bridges of long spans,
as practiced in America. At that time the
longest iron span in America was the central
tube of the Victoria Bridge at Montreal, 330
feet in the clear. Since then, several bridges
had been built with wider openings; and one
had lately been completed over the Ohio River
at Cincinnati, with a clear span of 515 feet.
This was the longest railway girder yet con-
structed, the next longest, the Kuilenburg
Bridge, in Holland, being 492 feet. The arches
of the Saint Louis Bridge were also 515 feet
span. Almost all American bridges of spans
exceeding 100 feet were pin-connected, instead
of being united by riveting. That plan was
preferred on account of the mathematical cer-
tainty with which the strains could be calcu-
lated, and the deflection or camber ascertained
—of the economy, ease, and celerity of erec-
tion, which for rivers subject to sudden floods
was a matter of vital importance — and because
it was believed that the parts of a bridge could
be more strongly united than by riveting, and
that a considerable reduction was possible in
the dead weight of iron.
Two of the latest and best examples of
American long span iron bridge constructions
were chosen for illustration. One was the
trussed girder bridge across the Ohio River at
Cincinnati for the Southern Railway — 515 feet
between the bearings, and erected on temporary
stagings of timber — designed and executed by
Mr. J. H. Linville. The other was the bridge
of three spans of 375 feet each, carrying the
same railway across the Kentucky River, the
engineer, in this case, being Mr. C. Shaler
Smith. Both bridges were noteworthy for
their economical design, and for their compara-
tively small amount of dead weight.
The Ohio Bridge consisted entirely of rolled
iron, pin connected. The girders were quad-
rangular, each 51| feet deep, the panels being
25f feet long, and the girders 20 feet apart from
center to center. The weight of iron in the
span of 515 feet was 1176 tons. With a total
load of 431 tons, the center deflection of the
east truss was 2-fe inch, with a permanent set
of TV inch, that of the west truss being 2 inch,
with no permanent set.
Advantage was taken by the engineer of the
Kentucky River Bridge, of two towers and sets
of anchorage, formerly constructed for a sus-
pension bridge across the canon, which had
not been completed. The first panel of this
bridge on each side was bolted to the towers,
and was then corbelled out panel by panel.
The towers were calculated to be strong enough
to carry 196 feet of projecting spans. At this
point the spans were supported by temporary
towers of wood. The corbelling out process
was continued until the above spans each
reached the main iron piers, which were built
up simultaneously, so that the two met in mid
air. Each half of the center span was then
corbelled out as before, until they met in the
center. At this stage of the work, the upper
chords being in tension and the lower in com-
pression, the former were nearer to each other
than the latter by a few inches. The method
of closing the gaps under the changes resulting
from alterations of temperature was then
described. Up to this time the bridge was a
girder 1125 feet long, continuous over three
spans. But while the abutments on the cliffs
were stationary, the iron piers rose and fell
under changes of temperature, and so varied
the strains on the web system. The shore
spans were therefore hinged at points 75 feet
from the piers, leaving a center girder 525 feet
long, supported by piers 375 feet apart. Both
of the web systems of diagonal rods were con-
solidated into one member at the point of
contrary flexure, and were separated again
after the hinge was passed. When the bridge
was tested it was found that the movement of
the lower chord tenons under the passing load
was l-£ inch. Every effort was made to secure
ORDNANCE AND NAVAL.
93
the uniformity of the modulus of elasticity of
every part of the ironwork. Nevertheless, the
variation in length, between the east and west
chords, was 1 inch in 1125 feet. When the end
spans were loaded with 277 tons, and the cen-
ter span unloaded, the central deflection was
1.52 inch, and the upward movement of the
central span was 2.83 inch. With the center
span loaded with 331 tons, and the end spans
unloaded, the central deflection was 3.5 inch,
and the upward movement of the cantilever
was 1.58 inch. With all the spans loaded, 814
tons in 904 feet, the center deflection of the
center span was 1.62 inch. The Kentucky
River Bridge occupied four months and four
days in erection, the average number of work-
men employed being fifty-three. The average
cost of erection was about £2 10s. per ton.
The weight of iron in the bridge was 3,654,271
lbs. The depth of the truss was 37| feet, and
its width was 18 feet. The iron pier at the
base was 28 feet by 71£ feet ; at the top it was
1 foot by 18 feet; and it was 177£ feet high.
This was one of the boldest and most original
pieces of bridge engineering in America. Both
it and the Ohio hiver Bridge were conspicuous
for economy of design. Economy of design
was obtained by proportioning all the parts of
a bridge with a similar factor of safety, and
then combining those parts into a whole; and,
secondly, by using such proportions of height
of girder, length of panel, and combination of
parts; also, such width apart between the gird-
ers, and such methods of bracing the twointo
a structure able to resist wind pressure or
shocks, as would accomplish the first requisite
with the least quantity of metal. The problem
could only be solved by a tentative process.
To show how this had been accomplished, the
author gave a table of the weight of iron and
other important data of some of the most con-
spicuous long span railway bridges constructed
in Europe and America, and contrasted several
of the examples cited. Finally, the author
stated that the workmanship of long span
bridges in the United States was generally first
class ; and that the price of American bridge-
work had fallen year by year, from £40 6s. per
ton in 1870 to £20 16s. per ton in 1877.
ORDNANCE AND NAVAL.
Torpedo Cases. — A train passed through
London recently conveying 100 wrought
iron cases from Newcastle to Woolwich.
These were torpedoes, each to contain 500
pounds to 1000 pounds of gun-cotton, and
when they have had a coat of red paint they
will be placed in the torpedo stores at Wool-
wich Dockyard, where there are at the pres-
ent time torpedoes by the thousand, of all
sizes ready for issue— the stores, notwithstand
ing the recent demands upon them, being
almost full. The new torpedoes have been
manufactured by Sir William Armstrong
at his Elswick factory under a contract en-
tered into only a few weeks since, and they
were delivered last night on one of the new
platforms of the branch line running into the
dockyard. As most of the contracts entered
into on the strength of the £6,000,000 are term-
inable at the 31st of March, the deliveries grow
in number and quantity as the month advances.
puN Carriages. — The Royal Carriage De-
\J partment is still very busy with all kinds
of work, among which are a number of carria-
ges for the 64-pounder guns on the well-known
Moncrieff counter-balance principle. Twenty-
five of these carriages are in the estimate for
the current 3rear, and it is intended to employ
them in the coast defences. A number of the
Moncrieff carriages of larger pattern for the
7-inch gun were manufactured several years
ago, and are in use at various home stations,
chiefly in Ireland and on the river Severn.
When elevated to deliver its fire the gun sur-
mounts a 5-feet 6-inch parapet, the recoil of
discharge bringing it down under cover for re-
loading. The pneumatic principle for elevating
guns required for overbank fire at siege works
is at present making but little progress, a
readier system of elevating the gun on a car-
riage having been adopted in view of emergen-
cies.
Utilization op Discarded Breech-load-
ers.— There are a number of 7 inch
breech-loading guns in store at the Royal
Arsenal, Woolwich, having been for several
years discarded in favor of more modern
weapons, but attempts are now being made to
utilize them. By chambering the gun and the
use of pebble power, which is comparatively
mild in its action, it has been found possible to
fire much heavier charges than originally pro-
posed ; but there is no expectation of making
the guns do the work of the 7-inch armor-
piercing muzzle-loaders. The latter, however,
weighs 7 tons, and is il feet ten inches in
length, while the breech-loader weighs but 82
cwt. and has a length of 10 feet. Colonel Key-
man, Royal Artillery, proposes to mount the
resuscitated gun on an ordinary wooden plat-
form fitted with hydraulic buffers, and the
service in which it will be employed is the de-
fence of positions where a battery fire is not
required.
Another Addition to the British Navy. —
The Brazilian Government has got rid of
a marine white elephant, and our Admiralty
has made another considerable hole in the
histoiic "six millions" by the transfer of the
powerful armor-clad vessel Lidependencia from
the Brazilian to the British flag. After spend-
ing between £600.000 and £700,000 on her con-
struction the Brazilians have come to the con-
clusion that the game is scarcely worth the
candle, and that smaller vessels wTould better
serve all purposes in South American waters.
The vessel in question was commenced in the
Tnames yard of Messrs. Dudgeon, after the
designs of Mr. Reed, in 1872, and launched in
October, 1876. She is of 9000 tons displace-
ment, with engines indicating 1200, but work-
ing up 8000 horse-power. She is provided
with a very prominent gun-metal stem, form-
ing a ram, and her dimensions are 300 feet
length between the perpendiculars, 63 feet ex-
treme breadth, and 50 feet height. The armor
plating is 12 inches thick at the water-line, and
from 9 to 10 inches in other parts. The arma-
94
VAIN NOSTRAND S ENGINEERING MAGAZINE.
ment consists at present of four 35-ton breech-
loading Wkitworth guns, placed in two turrets
protected by 13 inches of armor.
Thames Tokpedoes. — The torpedo arrange-
ments in connection with the Thames de-
fences are now complete. The station is at
Shornemead battery. The buildings erected
consist of magazine, connecting shed, cable
tanks, stores, &c. A jetty has been construct-
ed on piles and carried some distance into the
river, far enough to enable the torpedo launches
to embark or disembark at any time of the
tide. The whole arrangement has been carried
out under the direction of Colonel E. M. Grain,
commanding Royal Engineers at Gravesend.
The torpedoes will be moored, when required,
in various parts of the river, sinkers being at-
tached to them. Each torpedo so laid down
will be connected by an electric cable with one
of a series of bells, so that upon a ship touch-
ing a torpedo it will be instantly known in the
operating room, and, as the torpedoes are ex-
ploded from the shore, it will be at the discre-
tion of the officer in charge either to blow the
ship out of the water or let her pass on her
course. There will not be the slightest danger
to the ordinary road traffic, as the torpedoes
can only be fired by completing the electric
circuit, and this can only be done by the offi-
cers on shore.
Breech-loading Ahtillery. — Although ar-
tillerists still strongly favor muzzle load-
ing guns, it seems to have been determined to
gratify the advocates of breech-loaders by a
new course of experiments, and three guns are
being prepared at the Royal Gun Factories in
the Royal Arsenal, Woolwich, for the purpose.
One is an ordinary 32-pounder smooth-bore
gun, which is being converted into a breech-
loader on the French or screw-relieve system,
the thread of the screw being cut away in such
a manner that one-sixth of a turn releases it.
This gun being cast iron will not be rifled, and
it will fire only low charges and smooth-bore
projectiles — probably case shot alone. The
second experimental gun is one of the old 40-
pounder Armstrongs, already a breech-loader,
but the wedge which at presents lifts out at the
top will be constructed to slide out at the side.
The third gun is an Armstrong 64-pounder,
which is to be converted into a double-wedge
gun after the pattern of Krupp's German guns.
"While these guns are being prepared a trial is
being made at Woolwich with a large breech-
loader manufactured by Sir William Arm-
strong at Elswick, and submitted for experi-
ment. It weighs about 70 cwt., and is bored
and rifled for a 6-inch projectile. The gun is
fitted with the French breech system for pur-
poses of investigation. — Iron.
A Collapsing Boat. — Another trial of one
of Mr. Berthon's twenty-eighth feet col-
lapsing boats, designed for use in troop-ships,
was made in the steam basin, Portsmouth, on
the 17th inst., in the presence of Rear-Admiral
Foley, Mr. W. B. Robinson, Chief Constructor,
Mr. J. Elliot, Constructor, and the inventor.
Sixty blue-jackets and a coxswain were placed
on board, three pinnaces being in attendance to
pick them up should anything untoward occur.
The weight brought the boat down about a
foot in the water, leaving twenty inches of
freeboard to spare, and under these conditions
she was rowed around the basin with apparent
ease. But, although there was no collapsing
of the side, as in the previous experiment, the
boat, when subsequently examined by Mr.
Elliot, showed so many unmistakable signs of
distress and structural weakness as would have
probably proved fatal in a seaway. The de-
fect was again found to consist in the arrange-
ment of the diagonal shores which extend from
the foot battens to the under part of the gun-
wales or covering board, and which serve the
purpose of keeping the boat spread out when
actually in use. The shores are jointed in the
middle in order to allow the boat to collapse,
lashings being placed around the joints and
secured to an eye fixed in one of the longitu-
dinal frames, and others around the points of
the lappings for the purpose of keeping the
shores straight and the boat in form. Under
the strain to which it was subjected it was
found that the batten against the toe of the
shores had been forced out of its fore-and-aft
direction, and in one place broken, and that the
gunwale, which is formed of several breadths
bolted together, had opened and been bent.
As in a seaway the strains would have been
frequently localized, it seemed clear to the
officers that a collapse was only prevented by
the still water in which the trial was made.
— Iron.
BOOK NOTICES
Pine Plantations on the Sand Wastes
of France. Compiled by John Crodm-
bie Brown, LL.D. Edinburgh: Oliver &
Boyd.
The interest in Forest culture is rapidly in-
creasing in this country. It is only recently
that the public voice has been raised against
the useless destruction of woods already in
growth. Soon we shall hear of efforts to
raise extensive forests in sections where none
have grown before. The benefits of such tree
culture are manifold and lasting. In these
matters we naturally depend for advice of
people of older countries in which this indus-
try has been successfully pursued.
No writer within our knowledge has studied
the subject so widely as Dr. Brown, and no
one else presents so much information that is
valuable to tree culturists of the United
States.
The present work is especially of this latter
kind.
rPHE Journal of Forestry and Estates
1 Management. London: J. & W. Rider.
Subscriptions received by D. Van Nostrand.
Price $ti 00 a year.
The June number of this excellent journal
is at hand. Every issue presents something of
interest and value for tree growers in this
country.
In the absence of an American periodical de-
voted to this practical science, we can recom-
mend this journal to those of our readers who
are interested in forest protection or in forest
culture.
BOOK NOTICES.
95
La Methode Graphique dans la Sciences
Experimentales. Par E. J. Marey.
Paris : G. Masson. For sale by D. Van
Nostrand. Price $6.40.
This is a large octavo of 660 pages, present-
ing a collection of the various methods for
representing graphically the action of different
forces.
The phenomena treated belong chiefly to the
department of physiology. Some of the
methods are new; most of them are not,
Some of the devices for registering the
action of the heart, and for measuring the
force of its action are very ingenious.
The work is beautifully printed and illus-
trated with 348 wood cuts.
TRAITE THEORIQUE ET PRATIQUE DE LA
Fabrication du Sucre. Par E. J.
Maumenb. Tome II. Paris: Demod. Ftr
sale by D. Van Nostrand. Price $12.00.
The volume completing this extensive work
treats of the chemistry and physiology of all
plants employed in manufacture of sugar, the
culture of saccharine plants, the manufacture
of sugar, the sugar mills and the refining pro-
cesses, covering eight hundred pages of text,
and illustrated by 140 excellent wood cuts.
But few manufacturing processes are so
fully and ably treated, as is the manufacture
of sugar in this treatise of Maumene.
proceedings of the institution op clvil
Engineers.
Through the kindness of Mr. James Forrest,
Secretary of the Institution, we are in receipt
of the following papers:
Liquid Fuels. By Harrison Aydon.
Evaporative power of Locomotive Boilers.
By Atkinson Longridge, M. I. C. E.
Recent Improvements in Electro-Dynamic
Apparatus. By R W. H. P. Higgs, and J.
R. Brittle.
The first is illustrated with extraordinary
fullness.
In a future number we will present extracts
from the above papers.
The War Seips of Europe. By Chief-
Engineer King, United States Navy.
Portsmouth: Griffin & Co. London: Simpkin,
Marshall & Co. For sale by D. Van Nostrand.
Price $4.25.
This is virtually a reprint of a Report upon
European Ships of War, made by the author
to the Secretary of the Navy at Washington,
in 1877, and the information given is of great
value to all professional men, as well as to the
general public. Construction, cost, and speed
are considered, the advantages one ship has
over another is explained, and the strong and
weak points of each are pointed out. It ap-
pears that in the eight years (1866-74) our ex-
penditures on shipbuilding and repairs
amounted to £15,666,155. The repairs dur-
ing the above period are returned at the sum
of £5,164,475, for both ironclads and unar-
mored vessels. In the years 1866-67 the re-
pairs to ironclads cost £109,145, but in 1873-74
the outlay had risen to £291,381. The expend-
iture on unarmored ships on the same account
was, in 1866-67, £782,728, and in 1873-74,
£464,911. What will be most interesting to
readers at the present time, is the review of
foreign naval resources, though the bulk of
the work is taken up with our own. All the
Naval Powers are made to furnish materials
for the work. The book is amply illustrated,
a sheet of diagrams of targets fired at by the
100-ton gun, being among the excellent plates
given. The work has the value attaching to
it of being the testimony of a thoroughly in-
dependent critic. Though the book is espe-
cially adapted to naval men, the general public
will find it extremely interesting. — Iron.
rpHE Road Master's Assistant and Sec-
1 tion Master's Guide. By William S.
Huntington Revised and enlarged by Chas.
Latimer. New York: Railroad Gazette. For
sale by D. Van Nostrand. Price $1.50.
This improved edition of a useful book will,
we trust, be well received. The additions
have been made by a skillful and experienced
hand in railway construction.
The information afforded in the treatise is
given in a direct and concise way that will be
appreciated by the class of learners for whom
it is designed. Although technical in its
character, the subject matter of the book is
frequently a topic of absorbing interest to the
non-technical citizen. The question of greater
or less excellence in railway construction, in-
volving as it does the degree of safety in rail-
way travel, demands, at times, the close atten-
tion of people who are neither Road Masters
nor Section Masters.
Boiler and Factory Chimneys. By Robert
Wilson, A.I.C.E. London : Crosby
Lockwood and Co. For sale by D. Van Nos-
trand. Price $1.50.
This is a useful little work by a gentleman
who is in the habit of thinking out his subject
before he ventures into print. To many per-
sons it may appear that the building of a chim-
ney for a boiler furnace is a mere question of
good bricklaying, but, as a matter of fact,
many important questions must be decided be-
fore the bricklayer can be set to work. The
height and the area of the chimney will depend
primarily on the number and kind of boilers
employed, but several other factors must be
considered if a really satisfactory result is de-
sired, not excluding the prevailing direction of
the wind and the general atmospheric tempera-
ture of the district. When the size of the
chimney has been determined, its shape and the
form of the cap require study, and then last,
but not least, its stability must be seriously
considered. All these points are examined by
Mr. Wilson, who also writes a chapter on
lightning conductors, and gives us some in-
teresting figures in connection with notable
chimneys. The highest known chimney is
that at Mr. Townshend's Works, Port Dundas,
which, with the exception of the spire at Stras-
burg, the Great Pyramid, and the spire of St.
Stephen's, Vienna, is the loftiest building in
the world, rising to a height of 454 feet from
the ground, the total height of the brickwork,
&c, being 468 feet. This book forms an ex-
cellent supplement or complement to the
author's " Treatise on Steam Boilers." We
VAIN" NOSTRAND7S ENGINEERING MAGAZINE.
should mention that Mr. Wilson furnishes, by-
way of frontispiece, a useful table of dimen-
sions of chimneys from 30 feet to 300 feet in
height. — English Mechanic.
MISCELLANEOUS.
Artificial Stone. — A German patent (we
learn from Ding. Pol. Jo.) has lately been
granted to Dr. Zernikon, of Oderberg, for pro-
duction of artificial stones by boiling of mix-
tures of mortar. The chief constituents of the
stone's mass, sand and slaked lime, are known
to show great resistance to atmospheric influ-
ences. By boiling (according to the patentee)
a combination of silica and lime takes place ;
and the hardness of the mortar, petrified by
aqueous vapor, even increases by absorption of
carbonic acid from the air. The specimen
pieces show throughout the hardness of good
natural sandstone ; they are now about a year
old, and must have gained in hardness, for
shortly after casting they could still be cut
with the knife. Cracks and fissures are no-
where observed, and are hardly to be expected
in future, as the combination of lime and sand,
under action of hot water, is effected only at
such small degress of heat (between 120° and
150°), that a reduction of the lime hydrate to
free caustic lime cannot have taken place. As
regards the cost of production, the price of the
raw materials— 80 to 90 per cent, sand, and 10
to 20 per cent, slaked lime — will scarcely be
higher than that of clay for bricks. The time
of heating is nearly the same in both cases, but
the heating for bricks requires nearly a white
glow, whereas for the mortar stone it has only
to be brought to 150° C. ; thus theie is consid-
erable saving in fuel. The mode of forming
the prism-shaped stones is similar to that of
machine made bricks, where they are pressed
through a mouthpiece. All expenses of manu-
facture included, 100k. of the mortar stones, of
prismatic shape, cost about two marks. —
English Mechanic.
The Austrian Military Review gives some
particulars as to the underground tele-
graph lines which are being laid from Berlin to
the most distant extremities of the German
Empire. The first underground line completed
was that between Berlin and Halle, which is to
be connected with three lines from Berlin to
Cologne, from Berlin to Frankfort- on-the-
Maine, and from Berlin to Strasburg. The
lines from Berlin to Hamburgh and Kiel, from
Berlin to Breslau, and from Berlin to Konis-
burg' were then proceeded with. The Berlin-
Hamburg line is provided vuth two parallel
cables, each of seven wires ; and from Ham-
burgh one of these cable is continued to Kiel,
and the other to Wilhelmshafen and Emden,
where it is joined on to the North Sea cable to
England. The work of laying these cables is
very difficult in mountainous districts, but
along the high roads it is simple enough, and
of late the operation has been further simplified
by the use of a machine constructed for the
purpose. This machine, attached to a traction
engine, excavates the earth along the line of
route, and, having laid the cable in the ground,
throws it back again ; the only manual labor
required being that of the men who level the
soil afterwards. This machine was tried in the
presence of Herr Stephan, the Director of the
Prussian Post Office, upon the underground
line from Berlin to Spandau, by way of Char-
lottenburg, and was found to work very well.
Marshal von Moltke has despatched a detach-
ment from one of the " railway regiments " to
Spandau to make an underground passage for
the cable underneath the fortifications, and a
commission composed of civil engineers and
telegraph employes, has been appointed to ar-
range for laying dowm in the course of the
spring the lines from Berlin to Cologne, Frank-
fort, and Strasburg.
Torpedo Defences. — The torpedo defences
of the River Thames are now in a perfectly
complete and satisfactory condition. A com-
pany of Royal Engineers is stationed at Sheer-
ness on torpedo duty at the mouth of the
Thames and Medway, and the system of de-
fence is identical with that adopted for the pro-
tection of the various seaports, viz., the sub-
mersion of stationary mines attached by chains
to iron sinkers, connected by eleclric cable
with the shore, where the touch of a ship is in-
stantly registered and whence the torpedo can
at once be fired. Bermuda is now defended by
a regular system of submarine mines, complete
arrangements for the protection of the fort
having been planned and carried out since the
arrival at the station of the 28th company
Royal Engineers from England.
STEEL AND WROUGHT IRON PROJECTILES. —
Experiments are to be resumed at Shoe-
buryness for the purpose of gaining informa-
tion as to the peuetrative power of steel and
wrought iron projectiles and the resistance of
specially prepared targets. Some of the re-
sults already obtained have produced most un-
expected and surprising experiences, the most
remarkable being found durirg *a trial of a
composite steel and iron target. When fired
against the steel face of the target, the pro-
jectiles broke up badly, but when the target
was reversed the shot not only penetrated the
softer wrought iron, but went clean through
the steel as well. This is theoretically account-
ed for by the supposition that in passing
through the wrought iron the metal of the pro-
jectile gets set up into a more compact body,
and is therefore better able to endure the
shock of the heavier impact. This discovery,
if it be a discovery, is to be further investi-
gated, and in order to test it in the opposite di-
rection a steel projectile with a wrought -iron
face upon it has been made at the Royal
Laboratory Department, Royal Arsenal, Wool-
wich, and sent to Shoeburyness this week.
The storm flood, which caused such serious
damage along the Continental shores of
the German Ocean last autumn, has laid bare
some remains of the village of Eidum, in the
Island of Sylt, on the west coast of Schleswig
Holstein, which perished in the year 1436 by
the sea suddenly breaking over it and covering
it up. Stone foundations of former dwellings,
garden walls, and remains of various kinds are
now seen there.
VAN NOS.TRAND'S
ECLECTIC
ENGINEERING MAGAZINE.
NO. CXVI -AUGUST, 1878 -VOL. XIX.
THE THEORY OP INTERNAL STRESS IN GRAPHICAL
STATICS.
By HENKY T. EDDY, C. E., Ph. D., University of Cincinnati.
Written for Van Nostrand's Magazine.
II.
PROBLEMS IN PLANE STRESS.
Problem 1. — When a state of stress is
defined by principal stresses which are
of unequal intensity and like sign, i.e.,- in
a state of oblique stress, to find the in-
tensity and obliquity of the stress at o
on any assumed plane in the direction
uv.
Fig. 7.
Vol. XIX.— No. 2—7
98
VAN NOSTRAND'S ENGINEERING MAGAZINE.
In Fig. 1 let the principal stresses at o
be a on yy and b on xx ; and on some
convenient scale of intensities let oa=a
and ob=b. Let uv show the direction
of the plane through o on which we are
to find the stress, and make on perpendic-
ular uv. Make oa' = oa and ob' = ob.
Bisect a'b' at n, then on=£{a + b) and
na' =%(a— b). Make xol=.xon and com-
plete the paralellogram nomr; then is
the diagonal or=r the resultant stress
on the given plane in direction and in-
tensity.
The point r can also be obtained more
simply by drawing b'r \\ xx and a'r \\ yy.
We now proceed to show the correct-
ness of the constructions given and to
discuss several interesting geometrical
properties of the figure which give to it
a somewhat complicated appearance,
which complexity is, however, quite un-
necessary in actual construction, as will
be seen hereafter. It has been shown
that a state of stress defined by its two
principal stresses a and b can be separ-
ated into a fluid stress having a normal
intensity •§(« + b) on every plane, and a
right shearing stress whose principal
stresses are +J(«— b) and — \{a— b) re-
spectively.
Since the fluid stress causes a normal
stress on any given plane, its intensity is
rightly represented by on=-^(a-\-b),
which is the amount of force distributed
over one unit of the given plane. Since,
further, it was shown that a right shear-
ing stress causes on any plane a stress
with an obliquity such that the principal
stress bisects the angle between its direc-
tion and the normal to the plane, and
causes a stress of the same intensity on
every plane, we see that om=J(a— b)
represents, in direction and amount, the
force distributed over one unit of the
given plane which is due to the right
shearing stress.
To find the resultant stress we have
only to compound the forces on and omt
which give the resultant or=r
The obliquity nor is always toward
the greater principal stress, which is here
assumed to be a.
It is seen that in finding r by this
method it is convenient to describe one
circle about o with a radius of=^(a-\-b)
and another with a radius og=^(a—b)i
after which any parallelogram mn can
be readily completed. Let nr and mr
intersect xx and yy in hk and ij respect-
ively; then we have the equations of
angles,
noh=nho=^hio, noJc=nko=%hno,
moi = mio = \jmo, moj = mjo = %imo,
hence hn=kn=on=%(a-\-b)
.'. hk=a + b,
and rJc=rj=a} rh=ri=b.
It is well known that a fixed point r
on a line of constant length as hk=a + b,
or ijz=a—b describes an ellipse, and
such an arrangement is called a trammel.
If x and y are the coordinates of the
point r, it is evident from the figure that
x=a cos xn, y=b sin xn, in which xn
signifies the angle between xx and the
normal on.
x* i/2
.'. — 4-^- = l is the equation of the stress
ellipse which is the locus of r; and* cm is
then the eccentric angle of r. Also, since
noli^nho, nb'r—nrV\ hence b'r || sc^and
a'r || yy determine r.
In this method of finding r it is con-
venient to describe circles about o with
radii a and 6, and from a' and bf where
the normal of the given plane intersects
them find r.
We shall continue to use the notation
employed in this problem, so far as ap-
plicable, so that future constructions
may be readily compared with this. It
will be convenient to speak of the angle
xon as xn, nor as nr, etc.
PftOBLEM 2. — When a state of stress is
defined by principal stresses of unequal
intensity and unlike sign, i.e. in a state
of oblique shearing stress, to find the in-
tensity and obliquity of the stress at o
on any assumed plane having the direc-
tion uv.
In Fig. 8 the construction is effected
according to both the methods detailed
in problem 1, and it will be at once ap-
prehended from the identity of notation.
Since a and b are of unlike signs a + b
=on is numerically less than a—b—a'b'.
The results of these two problems are
expressed algebraically thus:
r*=±(a + by + i(a-by + i(a*-b*)cos2xn
.'. r2=J[a2 + 62+(«2-62)cos2£m]
or, 7-'x — a* eos'xn + b2 sin2cm.
INTERNAL STRESS IN GRAPHICAL STATICS.
99
If r be resolved into its normal and
tangential components ot=n and rt=t
then, n=%[a + b + (a— 5) cos 2xn],
or, n=a cos2a??i + £ sin2cm,
and,
tz=^ («— b) sin 2x?i= (a— b) smx?i cos cm.
It is evident from the value of the
normal component n, that the sum of the
normal components on any two planes at
right angles to each other is the same
and its amount is a + b: this is also a
general property of stress in addition to
those previously enumerated.
., t a—b
Also tan ??r-— -= — t
n a cot xn + o tan xn
The obliquity nr can also be found
from the proportion
sin nr : \{ci—b) : : sin 2xn : r.
In the case of fluid stress the equations
reduce to the more simple forms:
a=b=r=?i, t=0
For right shearing stress they are:
a=—b=-\-r, n=±a cos m,
t=±a sin m, m=2 xn.
And for simple stress they become:
b=0, r=a cos m, n=a cos.2m,
t=a sin m cos m, rn=xn.
Problem 3. — In any state of stress
defined by its principal stresses, a and b,
to find the obliquity and plane of action
of the stress having a given intensity r
intermediate between the intensities of
the principal stresses.
To find the obliquity nr and the direc-
tion uv let Fig. 7 or 8 be constructed as
follows: assume the direction uv and its
normal on, and proceed to determine the
position of the principal axes with re-
spect to it. Lay off oa'—a, ob'=b, in
the same direction if the intensities are
of like sign, in opposite directions if un-
like. Bisect a'V at n and on a'b' as a
diameter draw the circle a'rb' . Also,
about o as a center and with a radius
or=r draw a circle intersecting that pre-
viously drawn at r\ then is nr the re-
quired obliquity; and xx \\ b'r, yy\\a'r
are the directions of the principal stresses
with respect to the normal on.
Problem 4. — In a state of stress de-
fined by two given obliquities and in-
tensities, to find the principal stresses,
and the relative position of their planes
of action to each other and to the
principal stresses.
Fig. 9.
In Fig. 9 let nrl9 nr9 be the given
obliquities measured from the same nor-
mal on, and or^r^ or^—i\ the given in-
tensities. As represented in the figure
these intensities are of the same sign, but
should they have different signs, it will
be necessary to measure one of them
from o in the opposite direction, for a
change of sign is equivalent to increas-
ing the obliquity by 180°, as was pre-
viously shown.
Join rjr% and bisect it by a perpendicu-
lar which intersects the common nor-
mal at n. About n describe a circle
rxr^afbf; then oa' — a, ob'=b9 a'rx, b'rl9
100
VAN NOSTRAND'S ENGINEERING MAGAZINE.
are the directions of the principal stresses
with respect to rx and b'r2, a'r2 with re-
spect to r2, i.e., ob'rx=^xnx and ob'r2=xn2
.'. n1ni=ob'r2—ob'r1=:rJ>'r1=r2arr1
In case the given obliquities are of op-
posite sign, as they must be in conjugate
stresses, for example, it is of no conse-
quence in so far as obtaining principal
stresses a and b is concerned whether
these given obliquities are constructed
on the same of on, or on opposite sides
of it; for a point on the opposite side of
on as r3' and symmetrically situated with
respect to r2 must lie on the same circle
about n. But in case opposite obliquities
are on the same side of on we have
nxn%—ob'rx + ob'r^—rp'r^.
It is unnecessary to enter into the
proof of the preceding construction as
its correctness is sufficiently evident from
preceding problems.
The algebraic relationships may be
written as follows.
i(a—by=i(a + by + r*—r1(a + b)co8 n1r1
±(a-by=i{a + b) + r22-r> + %os n9rt
.'. (a + b)(r xcos nxrx—r.2cos n2r2)=rx*—r2*
Also (a—b)cos 2xnx + a + b=(2rxcosnxrx
(a—b)cos 2xni + a-\-b=2r^G08n2r2
which last equations express twice the
respective normal components, and from
them the values of xnx and xn^ can be
computed.
Problem 5. — If the state of stress be
denned by giving the intensity and
obliquity of the stress on one plane, and
its inclination to the principal stresses,
and also the intensity of the stress on a
second plane and its inclination to the
principal stresses, to find the obliquity of
the stress on the second plane, and the
magnitude of the principal stresses.
Let the construction in Fig. 9 be
effected thus: from the common normal
on lay off or, to represent the obliquity
and intensity of the stress on the first
plane; draw od so that nod=xni—xnx
the difference of the given inclinations
of the normals of the two planes;
through rx drawrxr2 perpendicular to od;
about o as a center describe a circle with
radius r2 the given intensity on the
second plane, and let it intersect rxr2 at
r2 or r2', then is nr2 the required obliquity.
This is evident, because «
xnx=nb'rx=^a'nrx, xn^nb'r^=$a'nr^
.*. nod=one=i(om\-{-onr2)
= 1 80° • — (xn2 — xnx)
If xnx and sm2 are of different sign
care must be taken to take their alge-
braic sum.
* The construction is completed as in
problem 4.
Problem 6. — In a state of stress de-
fined by two given obliquities and either
both of the normal components or both
of the tangential components of the in-
tensities, to find the principal stresses
and the relative position of the two
planes of action.
If the obliquities nrx, nr„ and the
normal components ot\=nxi ot^n^ are
given, draw perpendiculars at tx and t2
intersecting orx and or2 at rx and r2 re-
spectively.
If the tangential components lxrx=tx
and t2r^=t2 are given instead of the nor-
mal components, draw at these distances
parallels to on which intersect orx o?\ at
rxr% respectively. Complete the con-
struction in the same manner as before.
Problem 7. — In a state of stress de-
fined by its principal stresses a and b, to
find the positions and obliquities of the
stresses on two planes at right angles to
each other whose stresses have a given
tangential component t.
Fig. 9, slightly changed, will admit of
the required construction as follows: lay
off on the same normal on, oa' = d, obf=b;
bisect a'b' at n ; erect a perpendicular
ne=t to a'b' at n; draw through e a
parallel rxr2 to on intersecting orx and
or2 at rx and r2 respectively. Then the
stresses orx=rx, or2=r2 have equal tan-
gential components, and as previously
shown these belong to planes at right
angles to each other provided these tan-
gential components are of opposite sign.
So that when we find the position of the
planes of action one obliquity, as nr2,
must be taken on the other side of on,
as nr/. The rest of the construction is
the same as that already given.
Problem 8. — In a state of stress de-
fined by its principal stresses, to find the
intensities, obliquities and planes of
action of the stresses which have maxi-
mum tangential components.
INTERNAL STRESS IN GRAPHICAL STATICS.
101
In Fig. 9 make oa'=a, ob'=b and
describe a circle on a'b' as a diameter;
then the maximum tangential component
is evidently found by drawing a tangent
at r parallel to on, in which case t=a—bi
and rb'y ra the directions of the
principal stresses make angles of 45°
with on, which may be otherwise stated
by saying that the planes of maximum
tangential stress bisect the angles be-
tween the principal stresses; or con-
versely the principal stresses bisect the
angles between the pair of planes at
right angles to each other on which the
tangential stress is a maximum.
It is unnecessary to extend further the
list of problems involving the relations
just employed as they will be readily
solved by the reader.
In particular, a given tangential and
normal component may replace a given
intensity and obliquity on any plane.
We shall now give a few problems
which exhibit specially the distinction
between states of stress defined by
principal stresses of like sign and by
principal stresses of unlike sign, {i.e. the
distinction between oblique stress and
oblique shearing stress).
Problem 9. — In a state of stress de-
fined by like principal stresses, to find
the inclination of the planes on which
the obliquity of the stress is a maximum,
to find this maximum obliquity and the
intensity.
In Fig. 10 let oa'—a, ob' = b the
principal stresses; on a'b' as a diameter
describe a circle; to it draw the tangent
or0; then nr0 is the required maximum
obliquity and or0 the required intensity.
It is evident from inspection that in the
given state of stress there can be no
greater obliquity than ?ir0. The direc-
tions of the principal axes are b'r0, a'r0
as has been before shown.
There are two planes of maximum
obliquity, and or0' represents the second;
they are situated symmetrically about
the principal axes.
Bisect nr0 by the line od, then
oa'r0=yn .'. onr0=2yn, but
onrQ + nor 0= 90° or, 2yn + nr 0 = 90°
.'. ^nr + yn=450, but
odr0=doa' + oa'd .*. oc£r0=45°,
hence the line bisecting the angle of
maximum obliquity bisects also the
angle between the principal axes. This
is the best test for the correctness of the
final position of the planes of maximum
obliquity with reference to the principal
axes.
Fig. 10.
Problem 10. — In a state of stress de-
fined by its maximum obliquity and the
intensity at that obliquity, to find the
principal stresses.
In Fig. 10 measure the obliquity nr0
from the normal on and at the extremity
of or0=r0 erect a perpendicular inter-
secting the normal at n. Then complete
the figure as before. The principal
axes make angles of 45° at o with od
which bisect the obliquity nr.
The algebraic statement of Problems
9 and 10 is:
a— b
sin nr
a + b'
ab.
r0=a cot xn=-b tan xn .'. a=b tanacm
The normal and tangential compo-
nents are:
2r„
r0(a-b)
0 a + b9 ° a + b
Problem 11. — When the state of
stress is defined by like principal stresses,
to find the planes of action and intensi-
ties of a pair of conjugate stresses having
a given common obliquity less than the
maximum.
In Fig. 10 let nr^=-nr^ be thejgiven
102
VAN NOSTRAND'S ENGINEERING MAGAZINE.
obliquity; describe a circle on a'bf as a
diameter; then or^r^ or2=r9 are the
required intensities. The lines a'rx, b/r1
show the directions of the principal axes
with respect to orl9 and a'r\ b'r\ with
respect to orJ = 07\. The obliquities of
conjugate stresses are of opposite sign,
and for that reason ra' is employed for
finding the position of the principal
stresses. The algebraic expression of
these results can be obtained at once
from those in Problem 4.
Problem 12. — When the state of stress
is defined by the intensities and common
obliquity of a pair of like conjugate
stresses, to find the principal stresses and
maximum obliquity.
This is the case of Problem 4, so far as
finding the principal stresses is concerned,
and the maximum obliquity is then found
by Problem 9. The construction is given
in Fig. 10.
Problem 18. — Let the maximum ob-
liquity of a state of oblique stress be
given, to find the ratio of the intensities
of the pair of conjugate stresses having
a given obliquity less than the maxi-
mum.
In Fig. 10 let m\ be the given maxi-
mum obliquity, and n rx the given ob-
liquity of the conjugate stresses. At
any convenient point on or0, as r0 erect
the perpendicular r0w, and about n (its
point of intersection with on) as a center
describe a circle with a radius ni\ which
cuts nrx at r, and r2; then or-Z-or^=rl
-i-r2 is the required ratio.
It must be noticed that the scale on
which ort and or2 are measured is un-
known, for the magnitude of the princi-
pal stresses is unknown although their
ratio is ob'-r-oa1 '. In order to express
these results in formulae, let r represent
either of the conjugate stresses, then as
previously seen
-l(a— b)*=i (a + by + r*—r(a + b) cos nr
.•. 2r=(a + #)cos. nr±
[ (a + b) 2cosa m* — 4 ab~]%
Call the two values of r, i\ and r2;
and as previously shown r* = r1r^'i also
cos. nr0=r0-t-%(a + b)
ri_cosm* ~ (cosanr— cos2nr0)^
r,2~~ cos nr + (cosW— cosW0)^
When nr=o the ratio becomes
b 1 — sin nrn
a 1 + sin. nr
Problem 14.— In a state of stress
defined by unlike principal stresses, to
find the inclination of the planes on
which the stress is a shear only and to
find its intensity.
In Fig. 11 let oa' = ay ob;=bf the
given principal stresses of unlike sign;
on a'b' as a diameter describe a circle;
at o erect the perpendicular or0 cutting
the circle at r0; then is ora—r0 the re-
quired intensity, and b'r0, a'rQ are the di-
rections of the principal stresses.
It is evident from inspection that there
is no other position of r0 except r0'
which will cause the stress to reduce to
a shear alone. Hence as previously
stated the principal stresses bisect the
angles between the planes of shear.
Fig. 11.
Problem 15.— In a state of stress de-
fined by the position of its planes of
shear and the common intensity of the
stress on these planes, to find the princi-
pal stresses.
In Fig. 11 let or0=r0 the common in-
tensity of the shear, and orQb'—xn,
or0a'=yn the given inclinations of a
plane of shear; then oa'—a and ob'=b
the principal stresses.
The algebraic statement of Problems
INTERNAL STRESS IN GRAPHICAL STATICS.
103
, = — cos.2xn0> r0
ab=t>
14 and 15, when n0 denotes the normal
to a plane of shear, is:
a + b
a
r0 = + a cot X7i0 = + bt&n.x?i0,a=-b tan3cm0
Problem 16. — When the state of
stress is defined by unlike principal
stresses, to find the planes of action and
intensities of a pair of conjugate stresses
having any given obliquity.
In Fig. 11 let nrx be the common ob-
liquity, oa'=a, ob' — b the given princi-
pal stresses. On a'b' as a diameter,
describe a circle cutting orx at rx and r2;
then o?\ = rx, or^=r2 are the required in-
tensities. Also, since the obliquities of
conjugate stresses are of unlike sign, the
lines r/a', r/b' show the directions of the
principal stresses with respect to onxi
and r2a', rj)' with respect to cm2.
Problem 17. — When the state of stress
is defined by the intensities and common
obliquities of unlike conjugate stresses,
to find the principal stresses and planes
of shear.
In finding the principal stresses this
problem is constructed as a case of
Problem 4, and then the planes of shear
are found by Problem 14. The con-
struction is given in Fig. 11.
Problem 18.— Let the position of the
planes of shear be given in a state of
oblique shearing stress, to find the ratio
of the intensities of a pair of conjugate
stresses having any given obliquity.
In Fig. 11 at any convenient point ro
make orQb'=x?i, or0a/=y?i the given
angles which fix the position of the
planes of shear. On a'b' as a diameter
describe a circle; make nrx equal to the
common obliquity of the conjugate
stresses; then is or1-r-or1=r1-5-f,1the ratio
required.
The ratio may be expressed as in
Problem 13, and after reducing by the
relations
r*=—ab, rQ-~^(a + b) = — tan.2sm,
we have,
r, cos nr + (cos2??r-|-tan22£m0)^
r2 ~~ cos nr — (cos2?ir-f tan22cm0)^
When nr=o the ratio becomes
a_l+ cos 2xn0
b l — cos2xnn
STREET-CLEANSING IN PAEIS.
By M. VATSSIERE.
From " Annates des Fonts et Chaussees," Abstracts published for the Institution of Civil Engineers.
The cleansing of the public thorough-
fares in Paris, formerly undertaken by
the Prefect of Police, is now a function
of the Prefect of the Seine. The staff
consists of two chief engineers, one for
each group of arrondissements, one
group being sub-divided into three sec-
tions, each under the charge of an execu-
tive engineer; and the other into five
sections, similarly supervised. These
sectional engineers have under them
fifty-one superintendents and sixty-one
overseers, whose employment imposes
upon the municipal budget an annual
cost of 260,000 francs. The scavenging
plant is kept in a central depot, where
materials of every description are stored
and classified for ordinary and extra-
ordinary service, when snow and ice
render additional assistants necessary.
The depots contain supplies of chloride
of lime, sulphate of zinc, sulphate of
iron, and carbolic acid, as disinfectants;
and hydrochloric acid nitro-benzide (acide
de mirbane), as cleansing agents. The
chloride of lime, of a strength of 100° to
105°, is successfully employed for the
disinfecting of places tainted with urine
or faecal matter, also for the cleansing
of gutters carrying sewage water. Sul-
phate of iron and sulphate of zinc are
both used under the same conditions.
Sulphate of iron possesses the disadvant-
age of rusting objects to which it is ap-
plied. Sulphate of zinc is stronger in its
action, but costs a little more. It pro-
104
VAN NOSTRAND'S ENGINEERING MAGAZINE.
duces no smell, nor does it leave any
trace. It is much employed in summer
for washing and watering the basements
of the Halles Centrales, used for fish,
poultry, and offal. At a strength of J,
and mixed with three per cent, of sul-
phate of copper, sulphate of zinc makes
a good disinfecting liquor, which pre-
serves its qualities a long time and is of
great use in private houses. Carbolic
acid is not strictly speaking, a disinfect-
ant; it does not act like chloride on
putrid matter, but arrests and prevents
fermentation, doubtless by destroying
the spores. It is therefore always em-
ployed when it is desired to destroy the
germs of putrid fermentation. It is
used at a strength of about ■£$, say a
gallon of the acid to forty gallons of
water. At strengths of y^- and -g-J-Q it
gives good results for watering once or
twice a week in summer those parts of
the Halles Centrales liable to infection.
It is even used as low as l010() for water-
ing streets and gutters. Hydrochloric
acid is applied to urinals and slaughter-
houses. In places much encrusted with
tartar it is used at a strength of %.
Lowered to yV it cleans smooth walls
and flags sufficiently. In ordinary rins-
ings a strength of ^suffices. It leaves
a disagreeable odor behind, which is
however quickly dissipated. Mirbanic
acid (nitro-benzide) is more energetic
than the foregoing, but it produces a
disagreeable smell of bitter almonds, and
leaves a white film which has to be
washed off. It is used at the same
strengths as hydrochloric acid. The
annual cost for plant and disinfecting
materials of all descriptions is £ 8,800
(220,000 francs).
The engineers of the city of Paris are
also charged with the sweeping of the
roads, an area of 12,916,800 square yards
being cleaned between 3 and 6 a.m. in
summer and between 4 and 7 in winter.
The carts for removing the public and
private refuse work from 6 to 8 a.m. in
summer and from V to 9 in the winter.
The filling of each cart is attended to by
the driver aided by two shovellers, the
latter having to provide during the rest
of the day supplemental sweepings
wherever required, to rinse the gutters
twice a day, and to clear and disinfect
urinals, &c. These matters are ordinari-
ly finished by 4 o'clock in the afternoon,
except in unfavorable weather. The
engineers have all at their disposal a
staff of
fr. c. fr. c.
2,200 men at from 2 50 to 4 0 per day.
950 women " 0 20 to 0 25 per day.
30 children (boys) at 0 20 per hour.
In addition there are one hundred and
ninety mechanical sweepers, and as each
machine represents the effective work of
ten men, the total scavenging staff may
be considered as composed of nearly five
thousand laborers.
The mechanical sweepers which, after
numerous trials and much hesitation,
have been introduced into Paris are, the
English machine, improved by M. Sohy,
and the machine of M. Blot, the former
being preferred. The mechanism of
both is simple, works with regularity,
and occupies little space; it consists of
a frame-work upon two wheels with a
seat for the driver. At the back is
placed the sweeping apparatus, com-
posed of an inclined circular bass broom,
actuated by gearing driven from one of
the wheels of the carriage. By means
of a clutch the driver can from his seat
easily put the broom in or out of gear.
The machine is employed in all weathers,
and works as well on paved roads
as upon macadam or asphalt. Each
machine weighs rather over 14 cwt.,
and can be drawn by one horse. It
sweeps about 6,578 square yards per
hour. The cost of a machine is £40,
and its annual maintenance, exclusive of
renewals of the brush, £ 8. The cost of
a new brush is about £2 16s. (70 francs),
which will work for from one hundred
and sixty to one hundred and eighty
hours.
The Paris mud no longer possesses the
manurial strength of former times, and
in consequence the receipts derived by
the municipality from this source have
greatly diminished. It is at present dis-
posed of by public tender to responsible
contractors for terms of about four
years. For its removal there are daily
employed five hundred and twenty carts,
and nine hundred and eighty horses.
The average bulk removed per day is
about 2,223 cubic yards (1,700 cubic
meters).
When a fall of snow occurs, attention
is first directed to clearing the footpaths
and crossings, so as to insure uninter-
STREET CLEANSING IN PAEIS.
105
rupted circulation of foot-passengers.
The town scavengers sand the roads
wherever it is necessary for the carriage
traffic. At the same time numerous
auxiliaries are organized to remove the
snow from the principal thoroughfares,
in the order of their relative importance.
For removing the snow the General
Omnibus Company are bound by their
concession to furnish fifty wagons, and
carts are specially arranged for with the
providers of sand and gravel at the
beginning of winter, the contractors for
maintaining the public roads being also
bound to hold their carts at the disposi-
tion of the sectional engineers. In cer-
tain cases the half-melted snow is swept
into the sewers, especially those carrying
warm water. Melting by steam has
been tried, when a continuous jet was
introduced into a mass of banked snow,
but it melted very slowly at first, and
the melting ceased after the cavity had
increased to a certain size. Two descrip-
tions of snow plough are kept in store,
one for manual, the other for horse
power; but they have never been used,
as the coating of snow seldom attains
.sufficient thickness, and as it is too
quickly compressed and hardened by
the traffic. As a rule the sum al-
lowed in the budget, about £ 7,000,
suffices for the extra labor incurred; but
occasionally severe winters cause this
to be greatly exceeded, as in 1875-76,
when the increase amounted to £ 8,000.
Both hose and carts are used for
watering the thoroughfares, the former
for the boulevards, the avenues, and a
certain number of first-class streets.
The watering plant belongs to the
municipality. Three descriptions of
carts are in use, two heavy wooden ones
are now being superseded by the third,
Sony's cart, made of sheet iron. The
carts contain 220, 242, 286 gallons re-
spectively, and will water from 2,400 to
3,350 square yards. The watering by
hose is attended to by the ordinary
street cleaners, who can easily water
24,000 square yards in thirty-five min-
utes, deducting the time necessary to
connect the apparatus with the mains.
There are three hundred and twenty-two
water carts, which on the average dis-
perse 1,311,200 gallons of water over a
surface of 7,139,163 square yards. A
surface of 2,783,092 square yards is
watered by hose, and this system is
being greatly developed on account of
its convenience and cheapness. The
annual cost of watering is £18,000.
IRON AND STEEL FOR SHIPBUILDING, &o.
By W. W. KIDDLE, A. I. C. E.
From "Nautical Magazine."
It is a common saying that we live in
an age of progress, yet it may well be
doubted if advantage is fully taken of
all the great resources which nature has
pre-eminently conferred on Great Britain.
Not long since the whole country was
drifting into a self-complacency which
has severely injured trade, by unsettling
the minds of the majority of the working
classes as to the nature of the principles
which govern it. They appeared to
think that when prices were forced up by
combination to an unnatural level the
results were to stand forever. But the
rude shocks of competition and its con-
sequent results, have awakened English-
men to the fact that other countries can
successfully mine the coal, and smelt
the iron, and make huge castings, and
ply the loom, to an extent which at one
time seemed impossible. In defiance of
what trade delegates may hold forth or
workmen affect to believe, foreign manu-'
factures are gradually supplanting many
which at one time appeared to have ex-
clusively taken root in English soil.
Many great political economists also
affect to see no danger to our mercantile
supremacy in this flooding of the markets
of the world with the produce of our
rivals, and speak of the absence of capi-
tal as an insurmountable barrier to their
progress. Capital is the child of labor,
and where there are willing hands and
106
VAN NOSTRAND'S ENGINEERING MAGAZINE.
good security it will find a resting place
and fructify, as it ever does, under such
favorable circumstances; while, like the
sensitive plant of Central America, it in-
stinctively closes up at the approach of
danger. Holland has created capital
out of the sand dunes of the German
Ocean, the beds of morasses, and even
the bottom of her lakes, until individually
she is one of the richest countries in
Europe. With such evidence, can there
be a doubt of the ability of more favored
nations to follow a similar path. At no
remote period a foreign flag was not
often seen in any of the great commer-
cial ports of India, China, or the West
Indies; yet at this moment they have
nearly the whole of the heavy goods
trade, and no inconsiderable portion of
more valued freights. The steam fleets
of Hamburgh and Bremen may now be
met in America and the Spanish Main,
bidding for freights which were formerly
carried exclusively in English bottoms.
One of the great staples — tobacco— is
almost monopolized by a German line.
We all remember the witticisms which
were launched against the first attempts
of Germany to become a Naval power.
Punch is silent now, and finds other sub-
jects for caricaturing. It would add to
his fame if he were wiser in his conceits,
for the perseverance of a race which is
not to be daunted by failure, has already
made its mark on an element upon which
Englishmen, until recent times, imagined
they had no rivals. This has been ac-
complished under disadvantages which
might well have made a more favorably
placed people pause, as their limited
coast in the bight of the North Sea is
full of shoals, is low, is destitute of good
harbors, and is on a dead leeshore, with
all the prevailing winds. At one time
no undertaking ever offered a less chance
of success. It is now completed — ships,
crews, and harbors — and in a few years
the new creation will become an im-
portant factor in European complications.
Such a result proves that modern science,
backed by an indomitable will, can dis-
pense with accumulations of capital until
it can be exacted from conquered states,
a proceeding which the plundered will
neither forget nor forgive. The most
fatal weakness which can come over in-
dividuals or nations is the undervaluing
of an enemy, and it is one from which
England has suffered in a pre-eminent de-
gree in recent times. It caused the loss
of the thirteen colonies, the capture or
destruction of several men-of-war on a
subsequent occasion, the Indian Mutiny,
and many other disasters of a similar
nature. May she take warning from the
past and regulate her conduct according-
ly in the future.
In arts and manufactures the same in-
difference has begotten competition,
which has seriously affected the staple
industries of the country, and it is to be
regretted that a large portion of the in-
jury has arisen from causes which the
merchant princes of the last generation
would have scorned to entertain. The
Hindoo, after washing his highly-sized
cloth in the waters of the Ganges, does
not recognize it as the same material
which a few minutes before was appa-
rently thick and glossy. The African,
as he looks at his shattered hand and
broken gun-barrel, or, when face to face
with the wild beasts of the forest, finds
his powder will not send a bullet into
the head of the elephant or the buffalo,
curses the dishonest trader to whose
rapacity he may probably owe the loss
of his limbs or his life. If enormous
capital be absolutely necessary before
commercial enterprises can succeed, how
comes it to pass that America can pro-
duce rifles and send them to Constanti-
nople at a price which this country can-
not compete with ? How comes it to
pass that the artillery of the great armies
on the Continent and the heavy rifled
guns on the shores of the Bosphorus, the
Baltic, and the Mediterranean should be
the work of German forges, while not a
single order has reached this country
since the commencement of the Russo-
Turkish war? It would be idle to say
that this arose from a regard of the neu-
trality laws, or even from a higher prin-
ciple; the love of gain rises superior to
either. How comes it to pass that the
locomotives from the factories of the
United States are scaling the Andes, or
running on the plains of Peru, when the
roads on which they ply are the offspring
of English capital? How comes it to
pass that the iron castings and bar iron
of Belgium are constantly finding their
way into the seats of English trade, and
underselling rivals on their chosen
ground ? Instances might be multiplied
IRON" AND STEEL FOR SHIPBUILDING.
107
but there are unmistakeable indications
that every year the struggle for the cus-
tom of the world will become more in-
tense, and the results more uncertain,
unless the masters and working men of
England resolve to work together and
redeem a prestige which has been rudely
shaken by recent events.
To aid this great work, the genius of
the engineer is absolutely necessary, in
order to more fully develop the hidden
powers which nature only yields to pa-
tient research, and to make them service-
able to the uses of man. For centuries
the great work has been slowly progress-
ing, but artificial wants have, during re-
cent years, increased to such an extent
as to imply that the time has arrived for
the advent of one of those great inven-
tions or improvements which mark an
age.
For some time the consumption of fuel
perhorse-power has not sensibly decreased
and men have anxiously watched the nu-
merous experiments which have been
tried, with feelings akin to those who are
aware that the advantages with which
they commenced life are slipping from
their grasp. To regain that ascendency
another start is necessary, and when pa-
tient research has developed the means
by which one pound of coal will do
double its present amount of work, we
shall enter on a new phase of prosperity.
For the want of this factor, foreign mer-
chant navies have long been gaining on
the English as before described. When
it is discovered, the cheaply worked sail-
ing ship of the Northmen will disappear
as surely as the once famed and much
vaunted American liner has before the
Cunard and the Inman steamers.
At present, economy in manning and
equipment of steam vessels is carried, in
many instances, beyond the limits of
prudence and safety, therefore [retrench-
ment cannot be made under those head-
ings. Indeed, it is highly probable that
the State or the great insurance corpora-
tions will, before many years have
elapsed, step in and demand legislation
on the subject, for life and property
alike appear to suffer from its omission,
notably in the grain and coasting trades.
A steam ship of 1041 tons, recently
wrecked, had a crew of deck hands
amounting to four all told. In other
words, one seaman, one ordinary to work
the winches, the carpenter, and a boy.
This is an extreme, although not an ex-
ceptional case, but it goes to prove that
the most elaborate machinery cannot
economize any more in that quarter.
The only hope of a further reduction of
expense now depends on scientific dis-
coveries which may be utilized by prac-
tical men, until the whole carrying trade
of the country owes its transport to the
agency of mechanical power. The days
of propulsion by sail can never again be
highly remunerative around the shores
of the United Kingdom. Men may
lament the decay of ancient seamanship,
but cannot change the inevitable. They
may with equal reason regret the extinc-
tion of the Knights of Malta.
It appears singular that with- iron in
unlimited quantities in so many of the
counties in England, so little compara-
tive progress is made to utilize it. In
this particular we are far behind the
United States, although their command
of every species of timber for building
purposes is far in advance of that of the
United Kingdom. In all the principal
cities and towns the rafters, the shop
fronts, and fittings of every description
are cast or wrought iron, notwithstand-
ing the expense is far greater than what
it would be in England. From this fact
it is reasonable to assume that architects
still love to cling to old traditions in lieu
of entering on a new field. If by any
mode of reasoning they could be induced
to adopt the American system, the im-
pulse it would give to the workers in
iron cannot be estimated, and this with-
out injuring existing trades. Whatever
may be advanced to the contrary, as
matters of fact the introduction of rail-
ways increased the value of horses, the
introduction of iron shipbuilding, the
wages of shipwrights, and the more uni-
versal adoption of iron in the building
of houses would, in all probability, ulti-
mately increase the earnings of joiners
and house carpenters, by introducing
improvements of style which need not
be dwelt on here. However, the inexo-
rable laws of supply and demand will
assuredly force iron into more general
use, for year by year the supply of con-
vertible timber is growing less, and a
forest which has been once felled is sel-
dom replaced. If it were, at least two
generations must elapse before it reached
108
VAN NOSTRANlrS ENGINEERING MAGAZINE.
maturity. From this serious drawback
iron is wholly exempt, requiring but the
skill of the miner and the smelter to
raise it in unlimited quantities. In no
other country up to the present time has
the precious metal been found in such
workable sites, or so near to the fuel
which is required for extracting it. Yast
as the mines may be which are opened
up in the United States, their locality is
generally remote from the great arteries
and centers of commerce, thus rendering
the cost of transport a serious item be-
fore reaching the market. Under any-
thing like equal circumstances, this will
long be a drawback on the energetic
race across the Atlantic; so much so,
that however they may strive to rival
England in foreign markets, nothing
short of misunderstanding and strikes in
this country can give them a chance of
success. Unfortunately, they have been
of such constant occurrence during re-
cent years as to damp the spirits of those
enterprising men to whom the world is
so deeply indebted. It is not going be-
yond the limits of probability to state
that if the time which has been lost
during strikes in the shipbuilding trades
alone could be regained, the labor would
complete a coasting fleet of iron steamers
which might not only have tended to
equalize the price of heavy goods through-
out the United Kingdom, and to increase
our foreign trade by enabling coals to be
carried more cheaply to the Continent,
but what is of more importance still,
would also tend greatly to reduce the
death roll of the maritime population.
Unfortunately, a lamentable ignorance
of the principles of political economy on
the part of the leaders of trades' unions
has prevented this, and the seeds of dis-
trust between employer and workmen
have been so industriously sown, that
the two classes stand like rivals, possess-
ing no common interests.
Commerce has been likened to a hardy
plant which thrives best when untram-
melled with artificial help. When the
great political economist penned the
lines, strikes and lock-outs were un-
known; and when contracts were entered
into there was a chance of carrying them
to a successful issue on the basis of the
original calculation. All this has been
changed; and it is not long since the
iron workers of all denominations on the
Clyde remained out six months on strike,
in the vain effort to force wages beyond
the limits, which would not only debar
the masters from receiving renumeration
for the science and capital employed,
but likewise involve them in heavy
pecuniary loss. A few years since, £20
per ton could be demanded for the con-
struction of a first-class iron ship, which
now may be had for £12. Yet, under
the leadership of designing or misguided
men, the workmen essayed to dictate
unbearable terms to their masters. They
failed, as wrong always must, in the
end; and the loss which has arisen to all
concerned cannot be reckoned by the
amount of wages and unemployed capi-
tal, but by the distrust it has engendered
at home, and the encouragement it has
given to rivals abroad. America, hoping
that a recurrence of such catastrophes
will ultimately drive a large portion of
iron shipbuilding to her shores, has
already relaxed in its favor the terms of
that almost prohibitive tariff on iron and
steel, and in future all materials used in
the construction of ships are to be ad-
mitted free of duty. This is undoubted-
ly the first step towards a rivalry, which
at no distant period may become formid-
able, especially if great lines of native
steamships are ultimately established be-
tween the West Coast of America and
China and Japan. English-built vessels
now monopolize the lion's share of this
lucrative traffic; but Americans are not
slow to copy what is really useful.
Mr. Brassey touched on dangerous
ground when, at a recent lecture, he an-
nounced that the peculiarly-trained
touch of the English artizan made him
superior to any in the world. There are
grave reasons for believing that, when
circumstances call it forth, the hands of
our Transatlantic brethren will in no-
wise be less cunning than those of our
own. Up to recent times they have had
no inducements to finish their work in a
style similar to that of this country; yet
in many species of tools and agricultural
machinery they already take the lead.
Even the thoughful and highly-educated
German acknowledges this superiority,
and is calling on his Government to
more heavily weight the imports of the
ingenious and self-reliant inhabitant of
the New World. It is one of the
triumphs of the engineer that his genius
IRON AND STEEL FOR SHIPBUILDING.
109
has enabled this almost impossible inno-
vation to be accomplished — an innova-
tion which the most far-seeing men of
the last generation could not have an-
ticipated.
Shipbuilders appear to use iron 'more
extensively than the members of any
other profession. In none has it been of
such vital importance to the welfare of
the country, and its introduction was
most opportune. The woods best adapt-
ed for the purpose of the naval architect
had become scarce not only in England
and the Continent, but in foreign coun-
trifs. The African and Indian forests
had been felled in almost every accessible
locality on the banks of the great rivers
and estuaries, and that which still re-
mained inland failed to be of service for
the lack of transport. Statesmen were
talking of interdicting the felling of
oaks, except for the construction of ships
of war, when the substitution of an in-
exhaustible material set the question at
rest for ever; and the grand old trees,
no inapt representatives of the race who
dwell around them, have been spared to
adorn the landscape around English
homes.
A movement has recently been in-
augurated for the introduction of steel
in lieu of iron for shipbuilding purposes.
Of course, if successful, it will form a
new starting-point in the art of enabling
the merchant to have a vessel twenty or
thirty tons per cent, under the present
weight — no mean advantage in trades
where the carriage of dead weight forms
the most remunerative portion of his
business. The innovation will have to
be conducted with more than ordinary
skill and care, from the fact that a rent,
which might be of no practical import-
ance in a bridge or a viaduct, might » >e
fatal to a ship. The latter is subjected
to strains which test the peculiar quali-
ties of the materials forming the hull in
a very marked degree; so much, indeed,
that an unusually large factor of safety
is adopted by all the great corporations
when laying down their rules. Experi-
ence and careful study have barely mas-
tered the laws which are necessary to be
observed for the safe construction of iron
vessels, when new have to be adapted in
order that a higher classed metal may be
introduced to supply its place. Great
fficulties are certain to be met with at
the outset. One of these — corrosion —
appears to be almost insurmountable,
and likely to deter shipowners and ship-
builders from bringing it into extensive
use. There are others which, in a prac-
tical point of view, will always cause
anxiety, such as docking, or lying in the
tideway of a rapid river, notably the
Mersey, or the Thames, during strong
spring floods and- gales. The rough
knuckles of granite quays on a lee shore
require a ship, when docking, to possess
other qualities than elasticity and tensile
strength, if her sides are to be preserved
from bulging, or even fracture. In a
similar manner the iron-plated sterns of
the Runcorn flats, with their heavy
lading of coals, or salt, or iron, would
become dangerous to materials lighter
than those now in use. Therefore, in
making reductions, the laws of stiffness
will have to be considered as well as the
laws of strength, not only in what has
now been mentioned, but in another re-
spect still more important, which the
reader will no doubt readily comprehend.
The ship being a huge girder, with a top
and bottom flange, and a connecting web
in the form of topsiders, it is of the ut-
most importance for the true working of
the machinery that all possible rigidity
should be given to it. This cannot be
secured without a certain thickness of
the material employed, for, however
great the tensile strength may be, it is
only one of the indispensable factors de-
manded. The stems of the magnificent
steamships of the White Star Line,
during heavy weather, appear to rise
and fall through an arc of eight inches,
as measured by an imaginary line, on the
break of the forecastle, by an observer
close forward. A stronger but more
ductile material would probably increase
this to a dangerous extent. It is, there-
fore, evident that great caution and care-
ful experiments will be required before
steel can be largely introduced in the
plating of the larger class of steamships
employed in heavy carrying, and, it may
be added, heavy driving trades.
The breadth of lap in their steel plates
plight probably be increased with ad-
vantage in double riveting for stiffening
purposes, but not in single, for the caulk-
ing of the seam would present greater
difficulties in the latter than it now does.
It would not be desirable for this reason
110
VAN NOSTRAND7S ENGINEERING MAGAZINE.
to have a greater distance between the
edge of the plate and the periphery of
the rivet than what is universally allowed
by scientific and practical men to be the
best for all purposes.
There is still a doubt as to the effi-
ciency of steel rivets, and Her Majesty's
ships Mercury and Iris have been wholly
fastened with iron. Under these con-
ditions, the butts being the weakest part
of the structure, extra precaution should
be taken to make them approximate to
the strength of the plates they connect,
by an additional row of rivets wherever
the strain is great. This plan has in all
likelihood been adopted, otherwise the
stronger material will more severely test
the goodness of the joints than ordinary
iron plates would do. For three-fifths
of the length amidships, or in broadside
ships the whole length of the battery,
the butt straps should be treble riveted
from the sheer strake to the neutral axis.
The general custom now is only to double
rivet, with the exception of the sheer
strake. Messrs. Harland and Wolff
have, in the construction of their ocean
steamers, gone far beyond the require-
ments of any existing regulations on this
important point.
In the construction of men-of-war, ex-
pense is not so much an object as effi-
ciency, and no difficulties are likely to
crop up on questions of finance. But in
merchant ships, where economy is one of
the primary laws governing the owner
and the builder, the cost of an extra row
of rivets in a large number of butts be-
comes of grave importance in times of
high priced labor. Subjects of this
nature must be left to regulate them-
selves. It is the profession of the engi-
neer to ascertain what is practicable, and
when that is accomplished to leave the
monetary details in other hands. His
specialty is to make much out of little.
Good housekeeping is easy with unlimit-
ed means.
The mail steamers on the Atlantic can-
not, without serious risk, reduce the
thickness of the plates near the water-
line owing to the danger of penetration
by ice, which, in spring, may not only be
found in the neighborhood of the Grand
Banks, but in all the great commercial
estuaries from the Chesapeake to the
shores of Newfoundland. Anderson, in
his highly useful manual, says there are
no reasons for believing that iron is more
brittle in winter than in summer, but
qualifies the statement by adding that
his experiments were made under cover.
It is certain that seamen will not share
his opinion, for they have a great dread
of the action of intense frost on the
plating at the water-line when steaming
through an ice-field, especially if it be in
hummocks, or greatly denuded by the
weather. In this condition, it assumes a
lustrous greenish hue, not unlike the
tint of the glass which still may occa-
sionally be seen in the cottages of rural
districts. At this stage, granite scarcely
surpasses it in hardness, and numerous
accidents bear out the accuracy of the
seaman's reasoning. In the winter of
1874-5, a large percentage of steamers in
the North American trades met with
serious damage to their bows or propel-
lers, and one, the Vicksburg^ burst the
plates under the counter, and foundered
in the vain attempt to back out of the
pack. Of course, the theory nursed by
seamen may be erroneous, but they are
so thoroughly imbued with its correct-
ness, that only practical tests will con-
vince them that their assumption is
founded on prejudice. The advocates
for steel rivets assert that the defect
which exists from burning may be ob-
viated by more care in heating. What-
ever may be done within the walls of a
foundry, no precautions which can be
used in a shipyard will prevent it. Rivet
boys cannot be expected to study the
temperature when they and the riveters
are employed on piecework. Therefore,
until steel can be tempered to stand
without injury the same rough treatment
as iron, there is not much hope of its
being generally adopted in the construc-
tion of ordinary vessels, except for deck-
ties, stringers, and bulkheads. It is un-
fortunate that the stiffness as well as the
tensile strength of all parts which form a
ship are tried in turn. If she grounds on
a stony place, irregular bumps severely
punish the spaces between the frames,
and in some instances, puncture them
badly. In a heavy seaway, the decks,
sheer strakes, stringers, and bottom, are
alternately exposed to tensile and com-
pressive strains, and in docking or load-
ing on a rapid river, the side plating is
often tested to the utmost limits of en-
durance. Take, for an example, a case
IRON AND STEEL EOE SHIPBUILDING.
Ill
of a long steamer entering one of the j jury has been sustained by any vessel,
northern basins on the Liverpool side of I The American engineer was so much
the Mersey, which, during north-west ' pleased with the simplicity and efficacy
gales, have no shelter from the Cheshire ' of the plan, that he has since announced
shore. But for that peculiar action of . his intention of adapting it in all docks
the waves known to seamen as the un- \ or jetties, but in lieu of attaching them
dertow or backwash, it would, at times, like patchwork, they will, for the future,
be impossible to drop alongside of such ; form a portion of the permanent piling,
formidable walls. Occasionally, a sea There are good reasons for believing
rolls over the summit, as it might do in | that until experiments have convinced
the open, and sends showers of spray to j the shipbuilder of the degree to which he
a considerable distance. The danger is j may test steel, it will only be largely
in places increased by the want of a bold used in the construction of men-of-war
sweep at the corners, and also by the | of certain classes, and packets for Chan-
walls being built perpendicularly in lieu j nel service. In both, expense is not so
of with a slight
ordinary wear
curve. No amount of
and tear strains and
much an object as lightness and efficiency,
and neither are much subjected to the
punishes a ship so much as the treatment ; rude tests of strength which so frequently
they sometimes receive from these causes, | try the ordinary merchantman. Further,
which certainly might have been avoided j the cargoes of mail packets are seldom
when the works were planned. Injuries heavy, neither is space such an object as
are often visible in the form of bulged | to prevent all the important parts of the
plates, broken rivets, and cracked frames, ! hull from being made accessible for
and when the position of the ship is con- ] scaling and painting. Experience de-
sidered it is not to be marvelled at; she i monstrates that when this is carefully
is converted into a huge lever, with the carried out, there Is practically no limits
bluff of the bow for a fulcrum, and all j to the duration of the plate. Whether
abaft it for the long arm, to which may
be attached one or more tugs backed by
a powerful steam winch to break her
round.
Three years since, the writer was re-
quested to examine and report on the
construction of a new wharf on the
Hudson river, which was intended for
the use of the steamers of one of the
great mail companies. Through an over-
sight similar to that pointed out, the
corners were badly rounded, and to make
this defect more serious, they were lined
with deep angle plates from the platform
to mean low water level. The probable
danger was pointed out to the gentleman
who had designed the structure, and a
sketch sent to Liverpool to illustrate it.
Nature really holds in her laboratory an
antidote to oxidization is uncertain, but
we do know that up to the present time
the highest chemical science has failed
to find one. The greatest scientists have
not been rewarded with a glimmer of
success, although pretenders of all de-
nominations essay to make the world be-
lieve they have solved the great problem.
In despair, at the failure of numerous
patents, one of the largest steamship
companies in Liverpool has recently
given orders that common lead paint is
now only to be used. In the North
Atlantic trade, where ships do not re-
main long in port, this may stand well,
but in tropical seas or foul waters it
does not meet the case. A few davs of
No steps were taken to remedy the evil, ; calm weather under the equator, enables
one party alleging that it was not their j animal and vegetable productions to at-
tach themselves to a ship's bottom with
marvelous profusion, and when this has
commenced there are no means of check-
ing the advance of both.
It will be interesting to note if iron
and steel work harmoniously together;
under what conditions, if any, wasting
will occur to either, and whether the
business, and the other that the error, if
it was one, should have been pointed out
at an earlier date. The result was, that
the second steamer which essayed to
enter when the freshets were running
down, stove in one of her bows, thus
causing delay and expense. After the
mischief was wrought, the corners were
supplemented with circular turret-shaped \ superior tensile strength of one will be
projections, designed by the writer, and in anywise detrimental to the other. It
since their erection not the slightest in- 1 is scarcely possible that the former
112
VAN NOSTRAND'S ENGINEERING MAGAZINE.
occurs, but so many singular combina-
tions take place in Nature, that it will
be well to adopt every precaution. The
latter is worthy of consideration, from
the simple fact that the melting points
of iron and steel being different, ex-
pansion may cause irregularities in
practice which may not readily harmo-
nize. In certain anchorages, chain cables
after being submerged a few weeks are
deeply scored, so much indeed, that the
fiber of the iron stands clearly out, and
in places cells resembling the half-section
of those of the teredo navalis in timber
may be traced. Few who have not
examined a specimen of the links on the
spot, would credit that so much mischief
may be done to one of the hardest of
materials by some unknown cause.
When heaving in, the rust may be taken
off like paste. It easily washes away,
leaves no trace of weed or shell behind,
which almost infers that galvanic action
is the cause. Sailors attribute it to an
insect, but whatever it may be, the in-
jury arising from the submergence of a
few weeks exceeds the ordinary wear
and tear of years.
The above statement may be deemed
irrelevant to the question. It is simply
introduced to show that unexpected
causes sometimes throw serious obstacles
in the way of great innovations.
THE DRAINAGE SYSTEM OF GLASGOW.
From "The Engineer."
The irrefutable logic of hard facts and
dearly-bought experience has completely
dispelled the illusion which some time
ago prevailed to a very considerable ex-
tent, that not merely profits but large
fortunes were to be realized by the utili-
zation of sewage. It is now thoroughly
well known and acknowledged also,
even by those who are somewhat re-
luctant to make the admission, that raw
sewage cannot by any existing process or
chemical treatment be converted into an
artificial manure which will pay the cost
of its own manufacture. A large class
persistently refused to give the slightest
credence to this view of the question, al-
though it was supported and based upon
scientific reports, chemical analyses, and
the impartial statements of Royal Com-
missions, which must have carried full
conviction to the mind of any unprej-
udiced person. It was indeed nothing
but the actual loss of the money invested
in one or more of the numerous precipi-
tating schemes which finally and conclu-
sively demonstrated to the shareholders
the futility of their projects, and the
fallacy of their expectations. It has
been estimated that one well-known
company beguiled the public of a million
of money in their fruitless endeavor to
effect the desired remunerative conver-
As we proceed with our subject
sion.
it will be seen that the people of Glas-
gow are not likely to fall into this error,
formerly so prevalent. They appear to
be well aware of the specious and illu-
sory nature of the processes, and while
recognizing the suitability of the means
employed for accomplishing the purifica-
tion of the effluent water, they entirely
discard the idea of attaching any value
as a manure to the precipitated sludge.
We are inclined to consider that their
views in this respect are in the main
pretty correct. Towards the close of
last year a number of gentlemen were
appointed by the Town Council of Glas-
gow to visit certain large cities and lo-
calities in England, to examine into the
various systems in operation for the dis-
posal of sewage and refuse matter, and
to report upon them accordingly. Man-
chester, Leeds, Birmingham, our own
metropolis, Bradford, Coventry, Croy-
don, Halifax, and Oldham were all
utilized in this way.
The physical situation of Glasgow is
similar to that of London^ inasmuch as
they both possess the great advantage
derived from the contiguity of a large
tidal river. This offers at once a ready
and, in some measure, a natural outlet
for the sewage of the riparian city, and
so long as the volume of the sewage dis-
charged into it remains comparatively
THE DRAINAGE SYSTEM OE GLASGOW.
113
small, little or no harm is likely to result
to the community. But no sooner do
these conditions cease to obtain than the
health of the inhabitants begins to suffer
and the rate of mortality to increase. In
order that a river should be maintained
in a state of purity it is necessary that
some authority should be appointed to
take care of it. It certainly does not
absolutely follow that the constitution of
such an authority will ensure the river
being maintained in a pure and unpol-
luted condition. There is an excellent
body called the Thames Conservancy,
but if we are to believe the statements
of Captain Calver respecting the results
of the metropolitan sewage system, the
state of the Thames is not such as to re-
flect much credit upon its Conservators.
Notwithstanding this, we entirely concur
with the members of the Glasgow depu-
tation, that until a Board of Conservancy
is established for the Clyde, as recom-
mended in the report of Sir John Hawk-
shaw, no works for the discharge of sew-
age into that river can be undertaken
with hope of ultimate success. Con-
taminated as the Thames unquestionably
is by the enormous and continual dis-
charge of sewage into it, it is purity it-
self in comparison with streams such as
the Irwell and the Bradford Beck. It is
impossible to expect that rivers and
streams similar to those alluded to,
which have been permitted to become
nothing better than common sewers of
the foulest description, can ever be re-
stored to a state of purity until a Con-
servancy Board is established with
powers to deal summarily with all the
pulluting parties. The jurisdiction of
such a Board, moreover, should not be
confined to that portion of a river flowing
through any particular town or district,
but should embrace the whole drainage
area of the basin belonging to it. It is
the common, and, at the same time, very
just complaint of the inhabitants of many
of our large inland towns which are situ-
ated on the banks of small rivers, that it
is not only a great hardship and expense,
but a useless one as well, to compel them
to purify their sewage before it is al-
lowed to be discharged into streams
which are already rendered as foul as
they can possibly be by the filth of other
towns.
Although the population of Glasgow
Vol. XIX.— No. 2—8
is, in round numbers, about one-seventh
that of London, yet the sewage of the
former town ought not to be permitted
to flow into the Clyde without previously
undergoing "purification. The average
range of the tide at Glasgow harbor is
only about half that of the Thames at
the London Docks, and the average
velocity barely exceeds a tenth. Purifi-
cation of the sewage, either by irrigation
or precipitation, before discharging it
into the Clyde, is evidently more neces-
sary at Glasgow, where a small range of
tide and a feeble current prevail, than at
London, notwithstanding the great dif-
ference in the relative population. If
the sewage is to be purified by irrigation,
land must be obtained for the purpose.
In other words, an irrigation farm must
be established. With regard to this
method of dealing with this great sani-
tary question, the deputation came to
the conclusion that " irrigation presents
the most perfect means for the disposal
and purification of sewage." It was also
their opinion, founded upon the actual
facts placed before their notice, that un-
der certain favorable circumstances " a
sewage farm might be made to yield a
profit." The conditions are — the acqui-
sition of land at a reasonable distance
from any resident population; the pur-
chase or rental of it at a fair agricultural
value; and the distribution of the sewage
by the principle of gravitation. The
first of these conditions is no doubt ad-
visable, but not absolutely necessary.
In spite of several statements respecting
the alleged danger to the public health
by the establishment of sewage farms,
we believe that no reliable evidence has
been produced to show that any evil
effects have resulted from the existence
of such farms, or that the rate of mor-
tality has risen in any town or village in
proximity to them. As to the accuracy
of their conclusions that a profit might
be made, we might say that, up to the
present moment, experience tends all the
other way.
Of the many ingredients employed for
precipitating the solid constituents of
sewage, lime appears, in point of general
application, to possess advantages over
the others. It is cheap, can be readily
procured nearly everywhere, and accom-
plishes the purification of the effluent
sufficiently to enable it to be discharged
114
van ntostrand's engineering magazine.
into any river, the water of which is not
used for potable or culinary purposes.
The objections against its employment
are that its purifying effect is evanescent,
and that it produces rather more sludge
than some other systems. The first of
these objections is merely one of degree;
and with regard to the second, it may
be observed that when adequate means
have to be provided for the removal and
disposal of some hundreds of thousands
of tons of sludge, a few thousand more
or less are not of much consequence, in
comparison with the other merits of this
particular process. One very ready and
convenient plan for disposing of the
sludge precipitated from raw sewage is
to simply "run it to spoil," that is, to
apply it to the making up of, or raising
the level of waste and low-lying lands.
To such an extent has this system of dis-
posing of the solid contents of privies
been for many years carried on in Man-
chester, that having reference to the
large number of houses erected on land
made up in this manner, it has been said,
" Manchester is a town built upon dung-
hills." The idea is not by any means a
pleasant one, although time and the sani-
tary influence of natural causes may
have removed all noxious and deleterious
qualities from the once polluted founda-
tions.
The rate of mortality of any town may
be fairly considered as the real test of
the efficacy of its sanitary arrangements.
An examination of this rate in many of
our large towns reveals the very signif-
icant fact that the greater the number
of water-closets — or, in other words, the
greater the use of the water-carriage sys-
tem— the healthier is the town. London,
which is beyond all other cities that in
which this method of removing the sew-
age from habitations is most extensively
practiced, returns a rate, calculated on
an average of five years, of 22.9. That
of Coventry, in which town the number
of water-closets is six times that of the
privies, is 23.4. It is rather remarkable
— although from various circumstances
the case is somewhat exceptional — that
the rate of mortality is only 19 in Croy-
don, a place where the water-carriage
system is in full operation, and where ir-
rigation is the method employed for
utilizing the sewage. In Birmingham,
where the rate is 25.2, the water-closets
are in the minority; and in Manchester,
where the number is comparatively very
small, the rate rises to 30.0, and to 29.3
in Salford. Density of population can-
not be urged as an independent cause of
a high rate of mortality, because in the
last two instances quoted, in which the
rate is practically identical, the relative
densities are as three to one. A com-
parison between Halifax and the metro-
polis will also serve to show that there is
no necessary connection between these
two particulars. The former town has a
density of population of only 18 to the
acre, with an average death rate of 26.6.
The corresponding figures for London
are 45.7 and 22.9.
The report of the " deputation " con-
tains some final recommendations with
regard to the sanitary measures to be
carried out in Glasgow. The majority
of these are well known to every engi-
neer and local surveyor, although not
always put into execution by the cor-
porations under whom they act. It is
recommended that " water-closets in
small houses should be discouraged."
This would appear to intimate that there
should be in Glasgow one system of sew-
erage for the rich and another for the
poor, yet, in a sanitary point of view,
there should be no such distinction.
Otherwise there is the risk of the water-
carriage plan being considered in the
light of a luxury to be enjoyed only by
the wealthy. Some years ago this, no
doubt, was the case. Another of the
" recommendations " is to the effect
" that the ordinary privies and ashpits
be altered to the tub and pail system, to
be cleansed daily, as it has been carried
out in Manchester." It is a little singu-
lar that the deputation shouldv recom-
mend for adoption a plan which, it is
said, has earned for the city in question
the highest death-rate of all those we
have mentioned. The rate of mortality
in Glasgow itself is 29.9, so that it can
hardly afford to bear any increase.
For the purpose of hardening wood
pulleys, the pulley, after it is turned and
rubbed smooth, is boiled for about eight
minutes in olive oil. It is then allowed
to dry, when it will become exceedingly
hard.
APPAKATUS TO MEASURE STRAIN OF LATTICE GIRDER.
115
APPARATUS TO MEASURE DIRECTLY THE STRAIN TO
WHICH THE PIECES OF AN IRON LATTICE GIRDER
ARE EXPOSED.
By Prop. WILLIAM WATSON, Ph. D., late U. S. Commissioner.
description; application to a set of
bars; experiments on a lattice
girder; results.
In order to ascertain as accurately as
possible the amount of the tension, or
compression, produced in each of the
different iron bars which make up a
lattice-girder, the Orleans Railway Com-
pany caused numerous experiments to be
made
upon
long and 1.12
suits show
such a girder, 12 meters
meters high; and the re-
that in future a notable
economy may be obtained in such gird-
ers by a different arrangement of the
metal.
description of the apparatus.
In order to perceive directly the effect
produced upon each bar, to judge of its
nature, and to measure exactly its intens-
ity, whether it be extension or com-
pression, M. Dupuy, Chief Engineer,
devised the following apparatus; it con-
sists (Fig. 2) of an iron bar pierced at its
two extremities, with two holes, A and B,
exactly 1 meter apart; this bar is joined
at one end with a second bar pierced
with three holes, C, D, E, the distances
CD and DE being 5 and 100 centimeters
respectively, thus forming a bent lever.
Two holes, exactly 1 meter apart, are
drilled in each bar to be tested, the bent
lever is attached to it by the points A
and D and the test-load applied. Then
as the bar AD lengthens or shortens, the
two rods of the bent lever tarn around
the center C, and as CD is one-twentieth
of DE, it follows that the extremity E
passes over a space equal to twenty
times the amount of expansion or con-
traction of the bar. A graduated scale
serves to measure the space through
which the extremity E moves.
The apparatus was first tried by meas-
uring the extension of several iron bars
firmly fixed at their upper extremities
and supporting a scale-pan, upon which
weights were placed. In order to avoid
drilling the bars, saddles were screwed
very tightly upon them, one of which
supported one extremity of the bent
lever, and the other the pivot of the
index-hand. Also a second system of
bent levers, exactly like the first, was
placed behind the bar to correct the
small errors resulting from torsion.
Three bars were tested, of which the di-
mensions of the sections were (Plate I) 200
millimeters by 93 millimeters, 270 milli-
meters by 52 millimeters, and 157 milli-
meters by 36 millimeters, and the pro-
portional elongations were 0.09 milli-
meter, 0.18 millimeter, 0.28 millimeter,
0.37 millimeter, under a load of 2, 4, 6,
8 kilograms, respectively. These results
agree with those generally adopted, viz.,
0.50 millimeter under a load of 10 kilo-
grams per square millimeter of section.
The girder specially constructed for
the tests was formed of two flanges
united by lattice-bars at 45°. Each
flange was formed of two plates, at right
angles, held together by two angle-
irons. (See Figs. 1 to 5, Plate II). Di-
mensions of the lattice-bars: First set,
140 millimeters by 9 millimeters; the
second set are flanged and are 75 milli-
meters by 75 millimeters by 10 milli-
meters.
The top and bottom horizontal plates
are 220 millimeters by 20 millimeters;
the vertical plates 250 millimeters by 20
millimeters, and the angle-irons 100
millimeters by 100 millimeters by 12
millimeters. Each of these lattice-bars
had the measuring-apparatus described
above.
The upper and lower flanges of the
girder were connected to the walls by
jointed iron rods to prevent these flanges
from warping, and the testing apparatus
was applied at five equi-distant points of
the upper, and at five of the lower flange,
The girder was then successively sub-
jected to the action of uniformly dis-
tributed loads as follows : viz., 5,000,
10,000, 20,000, 30,000, 35,000 and 40,000
kilograms. The results of the last
tests, viz. : the observed and the computed
stresses upon the diagonals and upon the
upper and lower flanges, resulting from
a uniformly distributed load of 40,000
kilogrammes are given in Tables I and
116
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Plate I.
.2 S bi
y
* H
od ft
*■
IB ■
per meter.
Elongation.
0. 087 mm.
0. 183 mm.
0. '286 mm.
0. 376 mm.
0. 476 mm.
•■
longat
r mm.
ion.
SK
_ be ti tJD bi W)
Q.O COO o o
APPARATUS TO MEASURE STRAIN OF LATTICE GIRDER.
117
Plate II.
O
w
Q
M
c
o
H
CO
H
"ml 0^ SO'raO ^IBOg
118
van nostkand's engineering magazine.
Table III shows the observed and com-
puted stresses on the diagonals for the
case in which a load of 20,000 kilo-
grammes was concentrated in the middle.
KESULTS.
From tables it appears:
1st. That the stresses on pieces sym-
metrically placed with respect to the mid-
dle of the girder were nearly identical.
2d. That for the uniformly distributed
load the flanged diagonals were all com-
pressed.
3d. That the plane diagonals were all
extended except those near the middle.
4th. That the stresses on the diagonals
diminished in passing from the abutments
toward the center.
For the case in which the load of 20,000
kilogs. was concentrated in the middle it
appeared that the stresses on the diagon-
als of the first pannel were about one-
half those on the same diagonals for the
case of a uniformly distributed load of
40,000 kilograms.
Table II shows the stresses at five
equally distant points on each flange, and
extending over a length equal to half
that of the girder.
In this test the flanges had been weak-
ened near the abutments, a piece of the
horizontal plate 3m.30 long and 0m.010
thick having been cut away from each
extremity, thus reducing each flange, for
these portions, to the vertical plate, and
two angle irons.
CONCLUSIONS.
The results obtained by these experi-
ments showed that the effects produced
upon the lattice-bars were scarcely one-
half of those indicated by the common
formulae; and that toward the middle of
the girder the bars inclined toward the
points of support were extended, while
the other set were compressed, which is
contrary to the ordinarily received hy-
pothesis. It was also certain that the
rigidity of the joints of these girders,
the parts of which are carefully riveted
together, has a considerable influence
upon the strength and flexibility of lat-
tice-girders. It is very desirable to
measure the real effects which are pro-
duced upon the great lattice-girders of
bridges already constructed, and this ap-
paratus is well adapted to this purpose.
Tests of the Girder.
Table I —Load 40000 Kilogs. Uniformly
Distributed. (Stresses on the Diagonals.)
Stresses on the Plane
Stresses on the
Diagonals.
Flanged Diagonals.
o
Observed
Calculated
Observed
Calculated
1
+ 5418
-J
h 14140
— 5180
— 14140
2
+ 2520
- 11312
— 5320
— 11312
3
+ 1260 -
- 8484
- 420
— 8484
4
+ 882 -
- 5656
— 1120
— 5656
5
— 1890 1 -
- 2828
0
— 2828
6
0
- 2828
— 1386
— 2828
7
— 1400
- 5656
— 882
— 5656
8
+ 1820
h 8484
— 1890
— 8484
9
+ 4340
- 11312
— 3150
— 11312
10
+ 5600
- 14140
— 5166
— 14140
Table II.— Load 40000 Kilogs. Uniformly
Distributed. (Stresses on the Flanges.)
* Stresses on the
Upper Flange.
Stresses on the
Lower Flange.
O
Observed
Calculated
Observed
Calculated
1
2
3
4
5
—13306
—36115
—34998
—44387
—51216
— 21162
— 34699
— 47375
— 54118
— 56338
+ 4435
+29779
+32437
+37558
+42680
+ 21162
+ 37699
+ 47375
+ 54118
+ 563118
Table III.— Load 20000 Kilogs. Concen-
trated in the Middle.
(Stresses on the Diagonals.)
Stresses on the Plane
Stresses on the
Diagonals.
Flanged Diagonals.
m
O
Observed
Calculated
Observed
Calculated
1
+ 2394
+ 7070
— 2380
— 7070
2
+ 1512
+ 7070
— 1260
— 7070
3-
+ 1386
+ 7070
+ 280
— 7070
4
+ 3654
+ 7070
+ 840
— 7070
5
— 2268
+ 7070
— 980
— 7070
6
— 420
— 7070
- 2898
+ 7070
7
— 428
— 7070
r 2520
+ 7070
8
0
— 7070
- 2520
+ 7070
9
— 700
— 7070
- 1260
+ 7070
10
— 2100
— 7070
- 2142.
+ 7070
* On five equally distant points extending along one-
half the length of tne girder.
ON" STEAM BOILER EXPLOSIONS.
119
[In a recent letter to the author, M.
Dupuy, says: "This simple apparatus
has recently been used to ascertain
directly the resistance of the different
parts of a bridge — le Pont de Roland,
having a span 24.5 meters, consisting of
two lattice-girders; the results were very
remarkable and have verified the theory
held: by French engineers, by showing
that the riveting of the lattice-bars has
the effect of materially diminishing the
work done by these pieces. The appara-
tus should be applied only in those cases
in which the pieces to which it is fasten-
ed preserve their neutral axis unchanged
by the load between the points of attach-
ment and the apparatus."]
An account of the tests of this, and of
other bridges by the above apparatus,
the results obtained, and the modifica-
tions of the present theory of lattice
girders which these results seem to re-
quire, must be reserved for a subsequent
communication.
ON STEAM BOILER EXPLOSIONS, AND EXPERIMENTS IN
RELATION THERETO.
By Dr. HERMANN SCHEFFLER.
From "Organ fur die Fortschrittc des Eisenbahnwesens," Foreign Abstracts of tbe Institution of Civil Engineers.
The Author is disposed to refer many
boiler explosions to the creation of a
marked disproportion between the ex-
ternal pressure acting on the boiler
water and its internal temperature.
This may act in two ways: (1) as a pri-
mary cause of explosion where the tak-
ing off of the pressure produces a sudden
and violent generation of steam, the
shock of which is greater than the boiler
can withstand; (2) as a secondary cause
where a rent in the boiler produced by
some other means creates the dispropor
tion, and the ensuing generation of steam
comes in to render the explosion much
more violent and destructive. The
second fact is generally admitted, but as
to the former there are great differences
of opinion, and it is therefore desirable
that the point should be cleared up by
actual observation on the fluctuations of
pressure and temperature occurring with-
in steam boilers under various circum-
stances.
With this view the writer affixed three
thermometers (made specially for the
purpose by Messrs. Schaeffer and Buden-
berg) to different parts of the boiler of a
locomotive, viz., one in the front of the
boiler, close to the entry of the feed-pipe,
and, therefore, where the lowest tem-
perature might be looked for; the
second about the middle of the length
of the fire tubes, where the temperature
would probably be highest; and the
third in the front of the fire-box and
near its top. A large series of observa-
tions were taken of these thermometers
by competent persons, and at short in-
tervals. The results are embodied in a
table, which gives for each observation,
(1) the actual pressure at the moment as
given by the pressure gauge, in atmo-
spheres; (2) the readings of each of the
three thermometers; (3) the theoretical
pressure of steam corresponding to each
of these temperatures, as calculated by
the formula of Regnault. The observa-
tions fall into four groups according to
the following condition: (a) engine
standing, feed shut off; (b) engine stand-
ing, feed going on; (c) engine running,
feed shut off; (d) engine running, feed
going on. Separate observations were
taken with three different descriptions
of feed apparatus, viz., an injector, a
plunger pump, and two plunger pumps
combined. Separate series of observa-
tions were also taken when the pressure
was rising, and again when it was fall-
ing.
The pressure as given by the gauge
in every case differed from the theoreti-
cal pressure deduced from the tempera-
tures. As these latter always varied
among themselves, exact agreement was
of course impossible; but this was not
enough to account for the differences
observed, which may possibly be attrib-
uted to defects of the gauge, but should
120
VAN nostrand's engineering magazine.
rather be taken into account among the
general results of the experiments.
These are as follows:
(1) When the feed was shut off,
whether the engine was standing or run-
ning, the thermometers at the fire-box
and in the middle of the boiler gave very
nearly equal readings. At the smoke-
box end the temperature was somewhat
lower, but the difference was not above
5°.
(2) With the feed shut off, but with
rising temperature and pressure, the in-
dicated tension of steam in the steam
space was about 0.2 atmosphere (3 lbs.),
higher than the theoretical pressure at
the hottest part of the water: with fall-
ing temperature and pressure it was
about as much lower.
(3) When the feed was opened the
temperatures at the three places fell un-
equally; the fall being least in the mid-
dle, greater at the fire-box, and greatest
at the smoke-box near the entry of the
feedpipe.
(4) Where the feed was effected by an
injector these differences were least, not
exceeding '7°; with a single pump they
amounted in some cases to 9j°, and with
two pumps to as much as lV-i°> corre-
sponding to a difference of pressure of 2j
atmospheres (about 35 lbs.).
(5) A fall in the temperature of the
water was in all cases followed by a fall
in the tension of the steam; but when
the cooling was rapid this fall was less
in proportion to it, so that the actual
tension became higher than the theoreti-
cal pressure at the points of observation.
The greatest difference so observed
amounted to 2f atmospheres.
(6) While this held in general, there
were cases where, at the commencement
of the feed, the theoretical pressure at
the hottest point was for a short period
higher than the actual steam tension,
the greatest difference, however, not ex-
ceeding 0.43 atmosphere.
(1) When the injector was used the
temperature of the feed-water, imme-
diately before entering the boiler, was
from 40° to 60° higher than that of the
tender-water. This, of course, accounts
for the inequalities of pressure pro-
duced by an injector being much smaller
than by a pump.
(8) A sudden opening or closing of
the regulator produced an instant fall or
rise of the pressure gauge of about 3 lbs.,
or lj lbs. respectively, followed in gen-
eral by a slight recoil towards the origi-
nal standpoint.
(9) The opening of the regulator
caused a rapid fall of the thermometer
which at that moment stood highest, and
a rise of that which stood lowest,
amounting in each case to about 3^°,
thus producing an equalization of tem-
perature to the amount of about 7°,
The following general conclusions are
drawn from the above facts by the
writer:
(1) The supply of water by feed-pump
causes large variations of temperature in
the different parts of a boiler. These
act on the steam tension, but with the
general result that this tension is decided-
ly in excess of the theoretical pressure
due to the water temperature: thus
fortunately tending to retard, and not
to accelerate, the generation of steam.
(2) At the first moment of opening
the feed the converse is observed, the
steam tension being about 0.4 atmo-
sphere in defect of the theoretical press-
ure. The same holds to a smaller extent
when the feed is shut off, provided the
temperature and pressure are falling at
the time.
The explanation of the above facts is
obvious. When the pressure is lessened
by the steady abstraction of steam it
falls steadily both in the water and the
steam space. When the abstraction is
rapid (as with steam blowing off) the
water maintains for a time a higher tem-
perature than the steam space, with a
corresponding generation of steam.
When the pressure is lessened by actual
cooling of the water, the steam only fol-
lows it gradually, and keeps up for a
time a higher tension. The slight con-
verse effect, at the moment of opening
the feed, is accounted for by the addi-
tional consumption of steam due to the
feed-pump, and perhaps by a slight con-
densation of steam effected by the first
entry of the cold water.
(3) When the temperature and press-
ure are rising instead of falling, the
steam tension will similarly appear in
excess or in defect of the theoretical
pressure, according as the original cause
of the rise is a checked consumption of
steam or a more rapid generation. The
first case is shown in the experiments
INFLUENCE OF THE MOON ON THE EAETH'S MAGNETISM.
121
when the engine was standing, the
second on several occasions when it was
in motion.
(4) Wherever pressure is taken off
water, which is above the boiling point,
a sudden generation of steam must ensue.
This has been actually observed in the
experiments to take place to the amount
of J atmosphere under ordinary condi-
tions. In exceptional cases it might be
much greater, especially when the large
differences of pressure at different parts
of the boiler (sometimes amounting to
thirty lbs.} are taken into account. The
sudden spring of the pressure gauge at
the opening and shutting of the regulator
indicates the violent effects which rapid
changes of this kind would produce in a
mass of vapor at high tension. The
Author thus considers himself to have
shown that under a rare but not impossi-
ble combination of unfavorable circum-
stances, a sudden generation of steam
might occur violent enough to burst, if
not a new boiler, at any rate one
deteriorated by long working. At the
same time the much slighter effects of
this kind produced by an injector, as
compared with a feed-pump, should be
noted as forming a substantial advantage
on the side of the former.
INFLUENCE OF THE MOON ON THE EARTH'S MAGNETISM.
By JOHN ALLAN BROUN.
From "Nature."
There is a fact in connection with the !
moon's influence on our earth for which !
an explanation is necessary, and M. !
Faye has proposed for this end a hy- ]
pothesis in advance. He had already j
pointed out Dr. Lloyd's investigation I
which showed that the diurnal magnetic
variations could not be explained by the
hypothesis that the sun acts as a magnet.
But, it is said, " May the moon not ac-
quire induced magnetism under the
action of the earth, perpetually variable
according to the relative position of the
two bodies? If we consider the enor-
mous magnetic power of the earth, that
Gauss finds equal to that of 464 trillions*
of magnets weighing a pound each, and
if we remark besides that the distance
of the moon to the earth does not exceed
thirty times the length of this gigantic
magnet, we may give an affirmative
answer to the question proposed. But
then the magnetism induced in the moon
should in its turn exercise a small action
upon the proper magnetism of the earth
in the period of a lunar month. The
observations alone can decide this pro-
vided they are of great precision."
M. Faye then cites the results ob-
tained from the Toronto observations by
* M. Faye uses the word trillions, but the trillions are
English, not French, the latter being a very different
number.
Gen. Sir E. Sabine, that for the magnetic
declination showing a range of 0.64; and
he adds, " All these effects are of double
period; they show two maxima and two
minima in the course of the lunar month
of 29£ days, which proves that they are
due to an induced or reflex action, not
to a direct action of the moon herself."
I shall put my remarks on this subject
under three heads.
1. Is such a result possible for the
moon's synodical revolution ? Let us
commence with full moon at the winter
solstice; near this epoch the moon is in
the plane perpendicular to the ecliptic
passing through the earth's magnetic
axis and the sun. The north pole of the
terrestrial magnet is then presented to
the moon in such a way as to produce
the maximum of induction; when the
moon is near her third quarter the two
terrestrial magnetic poles will be equi-
distant from the moon and the inducing
action will be a minimum; there will be
a second maximum near new moon when
the south pole is most presented to our
satellite and a second minimum near the
first quarter. If now we follow the
earth in her revolution to the vernal
equinox, we shall find all this changed.
At full moon our satellite is then equi-
distant from the two terrestrial poles,
and the inducing action is a minimum;
122
VAN NOSTRAND'S ENGINEERING MAGAZINE.
it is a maximum, on the contrary, near
the first and third quarters. The con-
sequence will be that if any inducing
action existed it would have the same
value at all ages of the moon in the
mean of observations made during a
series of years, such as were employed
by Sabine for the variations in question.
Such a result, however, as has been
imagined by M. Faye might be possible
if, instead of the synodical, we employ
the tropical revolution of the moon,
which occupies nearly 27.3 days.
2. We may inquire, then, if the moon
as a permanent or induced magnet can
produce any magnetic variations ap-
preciable by our instruments? In the
first place, Mr. Stony has shown that if
the moon were as magnetic, bulk for
bulk, as our earth, her whole action in de-
flecting a freely-suspended needle in our
latitudes could not exceed one-tenth of
a second of arc (0".l). In order to con-
sider the question of the variable mag-
netism induced in the moon by our earth,
let us suppose her inductive capacity
equal to that of cast-iron. From Bar-
low's experiments at Woolwich with iron
balls I find that the magnetism induced
in an iron ball of one foot diameter is
about 2.0, in English units, which is
nearly twice the magnetic force given by
Gauss for the same volume of our earth.
Barlow found the induced moments of
different balls to vary as their volumes,
and assuming that the induced magnet-
ism varies inversely as the cube of the
distance of the inducing and induced
bodies, we find at the moon's distance
(60 terrestrial radii) the induced mag-
netism at the maximum, under the most
favorable condition, could not be more
than^'=ioWo o£ that s*PP°se<i in
the first case, that is when as magnetic
as the earth. Her whole action on a
magnetic needle here, then, due to the
earth's induction, could not exceed one
millionth of a second of arc. It is ad-
vantageous to get rid of hypotheses
which are so completely insufficient, and
we may put aside for the future any con-
sideration of the moon's action by her
own permanent magnetism, or by a varia-
ble magnetism induced in her by the
earth.
3. M. Faye has also misunderstood
the facts which he wished to explain.
The results obtained by Sabine have
reference to a variation which occurs in
24f hours, the lunar day, and not the
lunar month of 29^ days. The laws of
the lunar diurnal variations were ob-
tained first by Kreil for the magnetic
declination, and by myself for the mag-
netic force and inclination. This action
of the moon is, however, so very different
from what is generally supposed, and
from what was concluded from the first
investigation on the subject, that it is of
the greatest importance, in relation to
the whole question of cosmic meteoro-
logy, I should state some of the more
marked facts which have been deduced
from eleven years' hourly observations
on the magnetic equator. I shall limit
myself at present to the lunar actions on
the direction of the horizontal magnetic
needle.
The moon, in a lunar day of 24.7
hours, produces a variation in the earth's
magnetism, such that the magnetic
needle makes two complete and nearly
equal oscillations from an easterly to a
westerly position in the interval in
question. This is the general mean law.
We have seen, in considering the law
of the solar diurnal variations that, near
the magnetic equator, the law becomes
reversed when the sun passes from the
one hemisphere to the other, so that
when the sun is north, the movement of
the needle is like that in high north
latitudes, and when south, like that in
high south latitudes. If, then, the moon
acts in the same way as the sun, we
should expect a similar phenomenon for
the lunar diurnal variation when the
moon crosses the equator. This is not
the fact. The law differs little for the
position of the moon north and south of
the equator.
There is, however, an inversion of the
lunar diurnal oscillations; thus, in the
months of December and January the
north end of a magnetic needle is
farthest east when the moon is on the
upper and lower meridians, and farthest
west near moon-rise and moon-set;
whereas in the months of June and July
the reverse is the case, the north end of
the needle being farthest west when the
moon is on the meridian (upper and
lower) and farthest east when she is on
the horizon. It followed from this, as
for the solar diurnal law, that the
INFLUENCE OF THE MOON ON THE EAETH'S MAGNETISM.
123
oscillations should be in opposite direc-
tions at the same time in the higher
latitudes of the two hemispheres, as has
been found to be the case.
It is not then when the moon crosses
the equator but near the times when the
sun does so, that the moon's action is
reversed.
The dependence of the lunar action on
the position of the sun becomes more
evident as the investigation becomes
more detailed. When we determine the
mean law for each month of the year,
we find that the north end of the needle
moves equally far east and equally far
west at each of the two oscillations in
the lunar day; this is not found to be
the case for different positions of the
moon relatively to the sun. Thus in the
quarter lunations including full moon, in
the months of December and January,
the greatest west-east-west oscillation of
the needle occurs when the moon is on
the lower meridian; not when the moon,
but when the sim, is shining on the
place of the needle. The oscillation
from moon-rise to moon-set, that is to
say, while the moon is above the hori-
zon, is little more than one-third of the
oscillation for the half day when she is
below the horizon; the two westerly
extreme positions when the moon is on
the horizon are nearly the same.
Similar results are obtained for the
other quarter lunations. In all cases
that oscillation is the greatest of the two
for which the sun is above the horizon,
whether the moon be above it or not.
There are still some remarkable facts
connected with this variation at the
magnetic equator. Limiting our exami-
nation of them always to December and
January, we find, if we determine the
oscillations due to the moon for the day
when she is in conjunction and for each
of the six following days, that in the first
three days of the seven the oscillation is
west- east-west during the day, that is,
from sunrise to sunset; and in the last
three days it is east-ioest-east. In the
middle day of the seven the lunar action
is almost null; the oscillation of the
needle is very small, as we might expect,
since on that day the change at sunrise
from a loest-east to an east-west motion
takes place. The lunar hours of the
maximum and minimum extremes thus
oscillate about two hours on each side of
the mean, depending on the position of
the moon at sunrise.
The action of the moon, then, is
dependent on the sun's position rela-
tively to the equator (or the earth's posi-
tion in its orbit), and on the position of
the moon relatively to sunrise and sun-
set. But there is no relation between
the laws and amplitudes of the solar and
lunar diurnal oscillations. In the months
from which I have taken my illustra-
tions, the solar diurnal variation is a sin-
gle oscillation; that for the moon, how-
ever taken, for single days, for quarter
or for whole lunations, is always double.
Through the combination of all the vary-
ing modes in which this oscillation is
produced from day to day, the mean for
a lunation is a regular double oscillation.
The amplitude of this mean oscillation is
three times as great in January as in
June or July; whereas the amplitude of
the mean solar diurnal variation is a half
greater in June or July than in January.
I shall add another fact, one of the
greatest importance in connection with
this subject. We have seen that the
lunar diurnal Agnation changes in the
relative amplitudes of the two oscilla-
tions from day to day; the consequence
of this is that when the means for a
whole lunation, or even a quarter luna-
tion, are taken, the mean amplitude is
much less than that which is shown by
each day separately. Thus I have found
that the range of the mean lunar diurnal
oscillation for the lunation December 16,
1858, to January 15, 1859, at Tre van-
drum, was 1^25, while the ranges of the
mean oscillations for the quarter luna-
tions varied from l'.YO 2/.70, these
quarter lunations giving exactly the same
laws as have been deduced from eleven
years observations for the same lunar
epochs.
In order to understand the value of
these results we must compare them
with the ranges of the solar diurnal
oscillations for the same months; those
for December, 1858, and January, 1859,
were 2'.20 and 2'.24 respectively. And
as on some days the lunar diurnal varia-
tion has amounted 'to nearly 5'.0 (which
is equivalent to 12' in England with the
smaller directive force), it appears that
the lunar action is sometimes greater
than the solar action at the magnetic
equator.
124
VAN nostrand's engineering magazine.
As long as the lunar diurnal action was
considered to be of the minute character
first discovered, it was always possible
for the supporters of the heat thesis to
suspect that some small unknown heat
action was in question. Such an idea is
no longer possible. The lunar is some-
times greater than the solar diurnal
action; and the former is dependent for
its magnitude on the light and heat
vibrations due to the sun shining on the
place of the magnetic needle.*
If the solar light and heat vibrations
can increase the magnetic action, there
can be no difficulty in believing that
these vibrations may in their turn suffer
some modification of intensity. It would
* Mr. Willoughby Smith's experiments show that the
light vibrations o£ the ether in selenium diminish in a
very marked manner the electrical resistance of the crys-
tal ; and it does not seem improbable that the increase of
the lunar magnetic oscillation in sunlight may be due to
some similar action.
be difficult to measure small variations
of the sun's light with sufficient accuracy
as yet, though Mr. Willoughby Smith
has suggested a selenium photometer for
this end; we can, however, measure the
variations of temperature, and the fact
that the direct heating action of the moon
is inappreciable is no longer sufficient to
disprove the results of Madler, Kreil,
Park Harrison, and Balfour Stewart.
We have in fact a mode of lunar action
with which M. Faye was unacquainted
and could not take into account. The
whole basis of his argument is therefore
destroyed.
The view now given opens up a wide
field of inquiry, and cosmic meteorology
appears under another aspect. I hope
to be able at another time to present
other facts which seem to relate to mag-
netical and meteorological phenomena.
THE SEWAGE SYSTEM OF PARIS.
From "Engineering."
In anticipation of the intended visit to
the sewage system of Paris, by the In-
stitution of Mechanical Engineers, during
the forthcoming visit of that body to
Paris, we propose to bring together a
few notes upon the subject, which may
be found of interest.
The area enclosed within the fortifica-
tions of the city may be put down at
19,000 acres. The quantity of water
distributed for miscellaneous service
over this area per day is about 46,000,000
gallons, and the average daily rainfall is
some 22,000,000 gallons. About twenty
per cent, of this quantity is absorbed by
evaporation, leaving 54,400,000 gallons
to be dealt with. This water is loaded
with the debris from the streets, and the
impurities from manufactures, house re-
fuse, stables, <fcc. The sewage properly
so called does not enter the sewers, as it
is dealt with separately. Roughly speak-
ing there are about 100,000 water-closets
in Paris, of which a small proportion is
provided with separators that retain the
solid excreta, while permitting the liquid
portions to pass into the sewers; the re-
mainder are chiefly emptied into cess-
pools. The present system is of very
recent date, but partial drainage works
for conveying the sewage into the Seine
were constructed at a very early period.
In 1831 the remains of sewers dating
from the time of Philippe le Bel were
found underneath the Palais de Justice;
but the conduits then formed were only
for the service of a few palaces or other
important buildings. In early times the
Cite discharged its sewage into the
Seine, the University quarter on the left
bank, into the Bievre, and the town, pro-
perly so called, into the Menilmontant
brook. As for the neighboring slopes
of Charonne, Menilmontant, Belleville,
and Montmartre, the porous surface soil
absorbed a large proportion of the sew-
age, which — partially filtered— found its
way into the Seine. The brook of Men-
ilmontant was through several centuries
known as the main sewer of Paris, and
many roughly constructed channels were
made from time to time to converge into
it. About 1550 under the reign of
Henri II., a very important effort was
made to improve the condition of the
city. A scheme was prepared by an en-
THE SEWAGE SYSTEM OF PAEIS.
125
gineer of the period — Gilles Desfroissis —
to divert the water of the Seine into the
sewers and channels, natural and artifi-
cial, and by means of sluices to create a
constant current of water, which should
carry away all obnoxious matter down
to a suitable point of discharge. This
project, however, was opposed by the
city, and nothing came of it. In 1605,
under Henri IV., Prevot Francois Miron
arched over at his own cost the Ponceau
sewer, which extended from the Rue St.
Denis to the Porte St. Martin. In 1611,
Hugues Cosnier, director-in-chief of the
Loire Canal, revised the project of Des-
froissis but failed; in 1631, engineer
Pierre Pidou was charged with the work
of enlarging the city by enclosing within
the enceinte of the Tuileries, the Fau-
bourg St. Honore as far as the Rue
Royale, and the Faubourg Montmartre
as far as the present boulevards. In the
course of this work he made the sewers
navigable from the Arsenal to the Porte
de la Conference, and constructed near
the walls of the city a large sewer twelve
feet in width. At this time there were
about 12,000 yards of sewers of all kinds
in and around Paris, the greater portion
in so bad a condition that many workmen
employed in repairing them were killed.
It may be worth noticing that the physi-
cians of the period on inquiring into the
cause of these deaths, so far from recog-
nizing the real reason, reported that the
men in question were killed by the stare
of a basilisk which they asserted inhab-
ited the sewers. In 1667 the service of
police was created, and shortly after a
municipal ordonnance enjoined an annual
inspection of the sewers by the various
prevots, who were to take steps for their
maintenance. But in spite of this, mat-
ters went from bad to worse, the sewers
became choked and absolutely useless,
even to convey the sewage into the
Seine, where it had so long been a
grievance to the water-side population;
and on the 24th of April, 1691, a decree
was issued for the formation of a com-
mission to study the whole subject and
devise a remedy. In a map of Paris,
dated 1592, the brook of Menilmontant
as it then existed is shown. The banks
were sloped and planted with trees, and
its principal tributaries were the sewer
from the Rue des Egouts, between Rue
St. JIartin and Rue St. Denis, the Mont-
martre sewer, and the Gaillon sewer,
which afterwards was converted into the
Rue de la Chaussee-d'Antin. The land
in its vicinity was deserted, for no
houses could be occupied near it. But it
was not till about 1730 that extensive
operations were undertaken to ameliorate
the condition of the city. Michel-
Etienne Turgot, father of the great
minister, engaged seriously in the work;
he constructed an open channel in stone-
work, and provided means for its easy
cleansing, and he formed also a reservoir
at the end of this canal to receive the
contents of the Belleville sewers, which
then flowed through the canal. A map,
dated 1765, shows the extent of the
works carried out by Turgot. The canal
followed the Rue des Fosses-du-Temple,
where for part of its length it was arched
over, but was left open between the
Porte du Temple and the Porte St. Mar-
tin to receive the Sewer du Temple and
the Sewer de la Croix; it then passed
through the faubourgs of St. Martin, St.
Denis, Montmartre, and Poissoniere, and
was there partially covered over and
planted with trees. It was left open
again to receive the sewer of the Rue
St. Lazare, and passing beneatk Rue
de la Chaussee-d'Antin, it penetrated
through the Faubourg St. Honore, and
the middle* of the Champs Elysees, to fall
into the Seine. Gradually the work of
extending and improving the sewers was
carried on, and in 1806 there existed
about 79,'; 00 feet covered, with the ex-
ception of 5200 feet. During the reign
of Louis Philippe about 80,000 yards of
additional sewers were made; but their
usefulness was only partial, and the
sanitary condition of the streets was bad
in the extreme.
In 1855 the works which were to
transform the whole system of sewage
collection were commenced, the projects
having been previously elaborated by
the late M. Belgrand, Ingenieur des
Ponts et Chaussees. At that time there
were about 145,000 yards of sewers for
425,000 yards of streets, while at present
there exist some 775,000 yards of sewers
for 860,000 yards of streets. About
148,000 yards is the length of the service
drains of the dwelling-houses. The sys-
tem as now carried out is divided into
two classes, the sewers and the collectors;
the former receive the street and house
126
VAN NOSTKAND'S ENGINEERING MAGAZINE.
water, and conduct it to the collectors.
The latter are constructed along the
lower levels of the city to receive the
natural drainage, as well as the contents
of the sewers. They are three in num-
ber. The first is on the right bank of
the Seine, and is known as the Depart-
mental collector; it commences at the
point of intersection between the Rue
Oberkampf and the Rue Menilmontant,
and passes under the old boulevards.
Its course is broken by three bends, by
which it crosses the basin of La Villette,
the fortifications, and the Grande Route
St. Denis, until it falls into the Seine,
near the He St. Ouen. The sewage dealt
with by this collector is of the worst
kind, containing, as it does, the impuri-
ties from the abattoirs, gas works, the
factories of La Villette, Montmartre,
&c, and even the overflow from the
Bondy depot. The second collector on
the right bank of the river commences at
the Arsenal basin, following the quays,
and running under the Rue Royale, the
Boulevard and Rue Malesherbes, it tra-
verses the Route d'Asnieres and falls
into the Seine above the railway bridge.
At the Place du Chatelet it is increased
to receive the contents of the collector
of the Boulevard Sebastopol; at the
Place de la Concorde the sewer of the
Rue de Rivoli joins it; at the Place de
la Madelaine it absorbs the sewer of the
Petits-Champs, and at the junction of
the Boulevard Malesherbes and the Rue
de la Pepiniere, a sewer following the
course of the brook of Menilmontant
flows into it. On the left bank there is
only one collector, which at its com-
mencement absorbs the river Bievre,
that at one time used to flow into the
Seine above the Pont d'Austerlitz. The
collector taking this stream runs behind
the Jardin des Plantes, towards the
Boulevard St. Michel, when it passes
along the quays as far as the . Pont
d'Alma; here a double siphon takes it
across the river, when the gallery pass-
ing under the height of Chaillot and the
Avenue Wagram, crosses the village of
Levallois-Perret, and joins the collector
on the right bank last described, about
550 yards from the point of discharge.
Near the Pont d'Alma on the left bank,
it receives the Montparnasse sewer, and
the Grenelle collector; on the right bank
the Auteuil collector falls into it.
As an indication of the form and ar-
rangement of the galleries, we may give
a few particulars of the great collector
on the right bank, the course of which
has been already indicated. The section
is a gradually increasing one to accommo-
date the discharge from the various
tributaries flowing into it. The sewage
water flows in a channel, on each side of
which is a paved side walk, the whole
being inclosed within a semicircular
arch. The collector is composed of four
different types, Nos. 6, 5, 3, and 1. The
total 'length is 27,207 feet, and the
lengths of the different sections are re-
spectively 2296 feet, 2853 feet, 7019 feet,
and 15,039 feet. Type No. 6 extends
from the canal St. Martin to the Rue
St. Paul; type No. 5 from that point to
the Boulevard Sebastopol; type No. 3
from the Boulevard Sebastopol to the
Place de la Concorde; and type No. 1
from this point to the discharge at
Asnieres. Type No. 6 is 8 feet 2| inches
wide at the point of springing of the
arch, the height fi om the side galleries
to the point of springing is 4 feet llj
inches, and the side walls are curved
with a radius of 18 feet 9 J inches; the
width of the side galleries is 35j inches
on one side, and 15f inches on the other,
and the width of the channel is 31 J
inches. The depth of the channel in the
middle is 15f inches, the invert being
curved. The thickness of masonry is
lOf inches inside the invert, the bottom
of the structure being flat, 7 feet 6 J
inches wide. The thickness of the side
walls and arch is 13 inches, and the in-
terior of the sewer is covered throughout
with a lining of cement l^g- inches thick.
The outside of the arch is also protected
with cement. Type No. 5 is 9 feet lOy1^
inches wide at the springing of the arch,
the height of the side walls to springing
is 4 feet 1 1 J inches, and the radius to
which they are curved is 12 feet 9 J
inches. The widths of the side walks
are 27T9g- inches and 19-^- inches respec-
tively, and that of the channel is 47J
inehes. The depth of the latter is 31 J
inches in the center and 27T9g- inches at
the sides; the thickness of walls and
arch is 13 inches, and the thickness
underneath channel is lljj- inches. The
underside of the structure is flat and
about 6 feet wide; this, like all the other
sections, is lined throughout with
THE SEWAGE SYSTEM OF PARIS.
127
cement. Type No. 3 is 13 feet 1^
inches wide at springing; the height
from side walks to springing is 35-^
inches, and the side walls are curved
with the same radius at the arch, so that
the section of this type is more than
a semicircle. The side walks are both
27T9g- inches wide, and the channel is 7
feet 2j inches wide. The depth of the
latter is 39f inches in the middle and 3l£
inches at the sides, the thickness of
masonry under the channel is 17^
inches and at the sides it is 23§ inches.
The under side of this section is curved
on the exterior. Type No. 1 is 18 feet
3 inches wide at springing and 23 feet
7 inches wide on the outside of the
masonry, the arch is elliptical and the
height from springing to center is 6 feet
4 inches; the side walls are curved and
are 3 feet 5 inches high from the side
walks to the point of springing. The
walks themselves are 2 feet 11^- inches
wide, and the width of the channel is 1 1
feet 5 inches. The depth of the latter is
6 feet 11 inches.
The normal distances between the
underside of the masonry and the street
levels are as follows for the different
types except No. 1.
ft. in.
Type No. 8 16 6f
" No. 5 15 10TV
'•' No. 6 13 6T%
The gallery under the Boulevard
Sebastopol may be taken as a type of
one of the branch collectors. It was
constructed between 1855 and 1858
under one of the side avenues of the
boulevard from the Boulevard St. Denis
to the Quai de la Megisserie; from this
point it extends with type section No. 6
under the Boulevard de Strasbourg, as
far as the Rue du Chateau-d'Eau. In
ordinary work this gallery serves as a
collector for the flat district known as
the Marais; during heavy rains it dis-
charges the overflow direct into the
Seine, and renders impossible the floods
which used to be common in the
Faubourgs St. Martin, St. Denis, Mont-
martre, &g. In this gallery are laid the
two great water mains which receive
their supply from the Ourcq. The fol-
lowing are the principal dimensions of
the gallery:
ft. in.
Length 5074 0
Width at springing of arcli 16 0i|
Height from side walks to top of arch 11 11$
Width of side walks 2 7£
Width of channel 3 Hi
Depth " 4 3T\
Height of side walls 3 11^
Thickness of arch at crown 1 7^
" springing 2 11TV
Thickness of cement lining 0 lT3g
Distance apart of ventilators 164 0
" of street connections 32tf 0
Height of branch to street traps 6 6
Width " " 2 7|
The edges of the side walks of this
gallery, as well as of all except the
largest sections, are furnished with rails,
along which the wagons run, which are
employed for cleaning out the channels.
These wagons consist of a light frame
running on wheels and furnished with a
movable dam turning on an axis in the
wagon, and being manipulated by a
winch. Its form corresponds to that of
the channel. When it is desired to re-
move any obstruction in the channel the
dam is lowered, backing up the water
behind, which being suddenly released
carries with it the accumulation of sand,
mud, &c. For the larger sections,
boats are employed instead of the
wagons. These are built of iron, and
carry a movable dam in front similar to
that attached to the wagons. Project-
ing from the boat are two arms carrying
guiding wheels, which pressing against
the sides of the channel keep the boat in
the center. When the dam is lowered
the water behind it forms a head of from
6 inches to 12 inches, which is sufficient
to produce the desired effect. The
deposits accumulating below would
quickly form a bank that would stop the
progress of the boat, if the water in
escaping through the spaces between the
sides of the dam and the channel, and
by small openings made in the former,
did not drive the sand and mud con-
stantly in advance of the boat. The
rate of progress is very slow, as it takes
from eight to ten days to traverse the
five miles of the grand collector. In re-
turning up stream movable dams are
placed in the channel about every 600
yards, to reduce the speed of the current.
Safety chambers for the workmen are
placed at intervals of 650 feet. This
precaution is very necessary, since in
periods of heavy rains the collectors are
128
VAN NOSTRAND'S ENGINEERING MAGAZINE.
quickly flooded, as, for instance, on the
27th of July, 1872, when in five minutes
the Sebastopol collector was filled to the
roof, and several workmen were drown-
ed. There are about 7000 points of egress
for the workmen in case of necessity.
The number of men employed in cleans-
ing the sewers is about 700.
By means of the collectors nearly all
the sewage water is discharged into the
Seine far beyond the limits of the city.
But this is done at the expense of the
river lower down, chiefly on account of
the great deposits of material held in
suspension, since, as we have seen, the
house sewage proper is not admitted into
the collectors, but is removed from the
cesspools by carts. Dredging operations
are constantly necessary, and about
120,000 tons of debris are removed an-
nually from the Seine, at a cost of some
£6000. To obviate this evil, sewage
utilization works have been established
for some years on a comparatively small
scale at Gennevilliers, and larger ones
are now in contemplation.
A commission was lately appointed by
the Prefecture of the Seine to examine
into a project for the construction of ir-
rigation canals which should take the
sewage water from the collectors and
distribute it upon suitable land in the
vicinity of Paris, with the object of im-
proving the soil and also to convert the
impure waters into an effluent that
might filter gradually into the Seine. It
will be observed that this project is an
extension of the sewage utilization
scheme already carried on at Gennevil-
liers. The new project includes the con-
struction of a main irrigation canal ex-
tending from Clichy to the Forest of St.
Germains, of six secondary branches, and
of a large number of channels which col-
lectively should irrigate an area of
16,000 acres. .
The total length of the principal chan-
nel would be about 18,000 yards. It
would be circular in section, 6 feet 6
inches in diameter, and would traverse
the Seine three times by siphons in cast
iron. The pumping station would com-
prise five engines, collectively of 1200
horse power, of which two are already
at work in pumping the sewage for the
Gennevilliers' irrigation. The estimated
cost for these works is £ 160,000 for the
pumping station and irrigation canal,
&c.y £ 40,000 for the secondary branches,
or £200,000 for all, not including the
outlay made at Gennevilliers, which has
reached about £ 65,000.
The sewage utilization works at Gen-
nevilliers were commenced in 1869 upon
14^ acres of ground, and have gradually
developed until at the present time
about 600 acres are under treatment.
This land receives about 600,000 cubic
feet of water per acre per year. The use
of this water is quite optional, no culti-
vator is obliged to take it, and each may
use what quantity* he wishes, and apply
it in whatever way he judges best.
There are no data indicating the quantity
taken by each farmer, so that only the
average results are known.
The irrigated soil is generally laid in
ridges separated by trenches; the
trenches receive the water, and the
ridges are reserved for the plants. The
vegetable crops are here in advance of
all others, but a number of fields are oc-
cupied by potatoes, beetroot, cereals,
lucerne, &c. When it is desired to have
the soil less broken, it is only intersected
by small trenches, generally parallel,
and placed about 9 feet apart. The
general appearance of the crops is most
satisfactory. The vegetables, the quality
of which has been much criticised, are
excellent. The Horticultural Society of
Paris, which has followed with the
greatest interest the development of the
sewage farm at Gennevilliers, has spoken
of the success obtained in numerous re-
ports. At the bottom of the open chan-
nels by which the sewage is distributed,
there is a blackish deposit, formed by
substances held in suspension, mineral
and organic. At the moment of its
formation, this deposit seems impermea-
ble; but after having been exposed some
time to the air, it has the appearance of
a felt composed of hairs and vegetables
and other debris. This deposit is left at
the bottom of the trenches during one
crop, and is afterwards worked into the
ground. Stony ground, of which there
is a considerable quantity in Gennevil-
liers, is much improved by the deposits
of insoluble matters, mineral and or-
ganic, which the sewage waters leave
on its surface, and the amount of fertile
soil is thus gradually increasing from
year to year.
The scheme for the extension of the
THE BANKS OF JAPANESE RIVERS.
129
sewage utilization as elaborated by the
late M. Belgrand, is as follows:
At present two 400 horse power en-
gines raise part of the sewage water
from the collector at Asnieres. Two
other engines, established near the first
pair, would be sufficient to pump the
rest of the sewage. The invert of the
St. Denis is at a much higher level, and
could be discharged in the plain of
Gennevilliers by gravity. From the
pumping-station at Clichy to the forest
of St. Germain, for a length of 16 kilo-
meters, the water would be pumped
through a main; this conduit would pass
by the plain of Colombes, across the
Seine, in a siphon, at the Island of
Marante, would go through Bezons,
Houilles, Sartrouville, then a second time
over the Seine, and would enter the
northern portion of the forest of St.
Germain, where there are 3750 acres of
sterile ground, which irrigation would
fertilize; afterwards the water may be
sent in *a channel to Acheres, where the
irrigation would be extended over 1600
acres. The irrigable surfaces are ap-
proximately as follows:
acres.
District of Gennevilliers 2500 to 3000
District of Nanterre, Colombes,
Reuil 2500 to 3500
Districts of Carrieres, Bezons, Ar-
gente.uil, Sartrouville 3500
Forest of St. Germain 3700
District of Acheres 1750
The largest of these territories, that
of the forest, would be at the disposal
of the municipal service, and would con-
stitute an immense regulator, over which
the waters would run, and by which
irrigation of the other districts might be
controlled. For this reason this large
area constitutes one of the chief advant-
ages of the scheme.
JAPANESE METHODS OF PROTECTING THE BANKS OF
RIVERS.
By W. S. CHAPLIN.
Written for Van Nostrai^d's Magazine.
The Japanese have worked out orig-
inal methods of protecting the banks of
rivers. Perhaps the peculiarity of the
circumstances in which they are placed
has had much to do with this fact. The
rivers of Japan are all, in the upper half
of their courses, rapid mountain streams,
but nearer their mouths they become
sluggish and generally navigable. The
valuable land of the country is that
which lies low enough to be irrigated.
Hence the struggle, which is everywhere
apparent, to keep the streams in narrow
beds and retain the soil on their banks
for cultivation. In the lowland portions
simple earthen dykes serve to hold the
water ; but, at the points where the
rivers change from the rapid to the slug-
gish character earth would not resist
their action. At these points we find the
structures which are described below.
The simplest form used is a basket
about one and a-half or two feet in di-
ameter, and from six to thirty feet long.
Vol. XIX.— No. 2—9
This basket is filled with the rounded
pebbles, which are brought down by the
river, and are from six to ten inches in
diameter. The meshes of the basket are
made small enough to keep these pebbles
in. It will be seen that such a basket
when filled possesses many characteristics
which are valuable in engineering; they
are made of bamboo, which is always at
hand in this country, and are filled with
such stones as every river furnishes; they
adapt themselves to the bottom what-
ever its shape or the changes which take
place in it, and they can be made by an
ordinary laborer. Bamboo is said to de-
cay rapidly when exposed to heat, but
labor is so cheap, that, perhaps, it is as
economical in the end as it would be to
use a more durable and a more costly
wood. In many places these baskets
(the Japanese call them snake-baskets or
stone-baskets) are used to protect the
outside of earthen banks and are simply
laid against them, one resting on another.
130
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Fig. 1
THE BANKS OF JAPANESE RIVERS.
131
Fig. 3.
Fig. 4.
In such cases they are built or repaired
during the dry season in the summer.
Where a stronger current is to be re-
sisted, the whole bank is made of baskets
placed longitudinally, with a top layer
laid transversely. When the exposed
side needs repairs, another layer of baskets
is built against it, thus increasing the
strength of the bank at the same time.
To avert part of the current, but not
all of it, the Japanese use such structures
as are shown in Figs. 1, 2 and 3*.
These trestles are made of logs about
eight inches in diameter, lashed together
with rough hemp ropes. Three or four
feet from the bottom of the river there
is a platform, on which is placed the load
to keep the trestle in place. When the
water is low these trestles have but little
effect on its flow; but when it is high,
* The figures are from original drawings by a native
Engineer.
132
VAN nosteand's engineeeing magazine.
Fig. 5.
Fig. 6.
they turn away the force of it so that
the bank is somewhat sheltered, while the-
velocity is not so reduced that a deposit
is formed along the shore. To give still
more protection long baskets are placed
in front of the trestles as the figures
show. Where the velocity of the water
is very great the forms seen in Figs. 2
and 3 are used.
During low water a line of these
trestles is sometimes transformed into a
dam, in order to throw the water into ir-
rigation canals. To do this long logs
are placed at the water surface from one
trestle to the next. Then bamboos are
driven into the bottom along the logs
about three feet apart, so that the river
bottom supports the lower ends and the
logs the upper. Mats are placed against
the bamboos, and earth or sand is thrown
against the bottom of the mats. Such a
dam is very tight and effective until high
water comes; when the mats and bam-
boos are carried down stream, the logs,
being fastened only at one end, swing
around into the line of the current and
THE TRANSMISSION OF MOTION BY ELECTRICITY.
133
all possible space is left for the flow of
the water. Bamboo is very generally
used in all constructions for bank im-
provement; but other woods are used
where greater strength or framing is nec-
essary. Iron is never used, but all con-
nections are either made by lashing or
by mortices and tenons and pins. Figs.
4 and 5 show two common forms of crib
work; that shown in Fig. 4 is adapted
to soft bottom, and that in Fig. 5 to
rocky bottom. In both forms there are
platforms at about half their height
above the bottom, on which the loading
stones are placed.
Fig. 0 shows a peculiar form of crib
work. The frame is made of logs, and
the sides are filled in with bamboos
which are lashed to the cross pieces.
THE TRANSMISSION OF MOTION TO A DISTANCE BY MEANS
OF ELECTRICITY.
By M. CADIAT, Engineer.
Translated from "La Nature" for Van Nostrand's Magazine.
The employment of electricity for the
transmission of motion to a distance is an
accomplished fact. For some months, I
have controlled the machinery of a work-
shop, situated some distance from the
motor, with only such connection as was
afforded by a conductor of an electric
current.
The Societe du Yal d'Osne owns an
electroplating establishment at Paris, in
which copper-plating is constantly in
progress. The electricity was furnished
by a Gramme machine, which was run by
a portable engine at considerable expense
and trouble.
The idea of using two Gramme ma-
chines suggested itself to me. The ma-
chines have, heretofore, served for light-
ing the shops in winter. Machine No. 1
was attached to the horizontal shaft at
the millwright's shop. This was the
generator- of the electricity. The second
was placed in the electro-plating shop, 150
meters distant. This was the receiver of
electricity. The two machines were con-
nected by a double wire, The current
received at the second machine was
transformed into work, by which the
electro-plating machine was kept in mo-
tion.
It is a month since the plan was put in
operation, and there has been no irregu-
larity in its working. No superintend-
ence is necessary. The arrangement is
as simple as can be desired, and the mo-
tion is started or stopped by simply con-
necting or disconnecting the conducting
wire.
One advantage of the system lies in
the ability to vary the velocity of the
receiving machine. It is accomplished
by varying the resistance of the con-
ducting wire. Thus the velocity of the
machine No. 2, being 750 revolutions, if
a copper wire two meters long, and one-
and-a-half millimeters in diameter, be in-
troduced into the circuit, the velocity is
reduced by forty revolutions. If an iron
wire of one-and-a-half meters in length
and -^of a millimeter in diameter be
used, the velocity is reduced by 100
revolutions.
When the portable engine was em-
ployed to run the electro-plating machine,
the expense was about twenty-four francs
per day. Now the cost is inappreciable.
For if there is any extra consumption of
fuel in the driving engine at the mill-
wright's shop, it is not noticeable, and
the engineer cannot detect the stopping
or the starting of the Gramme machines
by any irregularity of his motor, which
is only a ten horse-power engine.
When the No. 1 machine is employed
for lighting purposes, it absorbs a sensi-
ble amount of the power of the engine.
It is estimated to require in general two
horse power for its successful working.
This is certainly not the last that is
to be said upon this question. We have
employed two machines used for lighting
and not designed for the purpose for
which they are employed. We do not
flatter ourselves that we have obtained a
maximum result.
Should the two machines have the
134
VAN NOSTEAND'S ENGH5TEEKING MAGAZINE.
same or even similar dimensions ? Ought
the first to possess higher tension or
greater quantity than the second ?
These questions are yet to be answered.
At present we are content to announce
that the transmission of motion to con-
siderable distance by an electric current
is a practical possibility.
WOHLER'S EXPERIMENTS ON THE STRENGTH OF GIRDERS
AFTER REPEATED CONCUSSIONS AND STRINS ON IRON
BRIDGES.
By Dr. E. WINKLEE, Professor of the Polytechnic School at Vienna.
From Foreign Abstracts of Institution of Civil Engineers.
The Author discusses the results of
Wohler's experiments on the effect of
repeated strains and blows on iron, and
attempts to apply these results to iron
girders, most of Wohler's trials having
been made on axles and tires. The
Author points out the empirical nature
of the present calculations for wrought-
iron bridges, showing that the most
elaborate analytical work is in -practice
nullified by the fact that the immediate
effect of the blows received by a girder
from the moving load, as also the ulti-
mate effect of these blows lasting for
years, have not yet been expressed in a
mathematical form, and have not been
introduced in the usual formulae. The
consequence is that engineers have been
obliged to assume so large a margin of
safety that accurate calculations of the
cross sections of iron are to some extent
useless; for, the effect of the forces
above mentioned not being ascertained,
the bridge may be a great deal too
strong, or even not strong enough.
After alluding to the great, increase in
the weight of locomotive engines in the
last ten years, which has diminished the
margin of safety in the old girder
bridges, Dr. Winkler considers the
effect of the permanent load in compari-
son with that of the passing trains, and
comes to the conclusion, that the heavier
the girder, the less will be the immediate
as well as the ultimate effect of the mov-
ing load on the iron: in other words, the
margin of safety should be greater for
bridges of small span than for large
ones. Messrs. Klett and Co., of Nurn-
berg, have constructed many bridges in
Germany, on the principle that the ad-
missible strain per square inch on
wrought iron should be 3f tons per
square inch for bridges of 30 feet span,
increasing to 4f for 250 feet span, and
to 5g tons for 460 feet. The Author
then proceeds to consider the ultimate
effect of repeated strains without shocks,
such as are produced by a passing train,
and explains why he thinks Wohler's
results on axles to be applicable to gird-
ers. The rules he deduces are the fol-
lowing:
1. Fracture occurs sooner, i.e. through
a less strain per square inch, if a load is
removed and frequently reimposed, than
if the same load is permanent.
2. The less the strain produced by the
moving load, the oftener must it be re-
moved and brought on again before pro-
ducing fracture, i.e. the longer will the
girder last.
3. The number of separate loadings
required to produce fracture is greater,
in the same ratio as the maximum strain
is greater.
4. If the maximum strain of a moving
load never reaches a certain limit (which
Launhardt calls "work-strength"), frac-
ture will never occur.
5. This "work- strength" is larger if
the strain produced by the permanent
load is larger.
Wohler's experiments, which lasted
from 1859 to 1870, were continued by
Professor Spangenberg at Berlin up to
the year 1873, and the above laws were
confirmed. The Author adds tables
showing the calculated strains and those
resulting from' experiments, the differ-
ences being but slight. The Author also
attempts to establish a mathematical
curve for the "work-strength," and com-
pares it with others calculated by Gerber
GEOLOGICAL KELATIONS OF THE ATMOSPHERE.
135
and Launhardt. He next considers the
effects of repeated moving loads on the
resistance to compression, the previous
work having applied to tension only.
The experiments made in this respect are
hardly sufficiently numerous; but with
the results arrived at, the effects of mov-
ing loads often repeated but without
concussions or blows are gone into, the
cases of tension only, compression only,
tension greater than compression, and
compression greater than tension, being
all separately considered. Having es-
tablished rules for these cases, the
Author discusses the effect of repeated
blows, which he compares to a weight
equal to that on the driving wheels of a
heavy engine falling through a height h\
he again, however, repeats that the ex-
periments are as yet incomplete, and do
not prove that the effects of the shocks
of an engine are really similar to those
! of a weight falling on the girder. An
' investigation of these effects on a girder
| already strained by the moving (but not
| striking) load, as described in the pre-
i vious section, then follows, and all the
cases of compression and tension, and
\ both, are separately considered, the con-
clusion being that the actual strain
which obtains by the rapid passing of a
heavy engine is greater than the strain
! resulting from the calculation of the
! moving load alone in the proportion of
about 1.3 to 1.0, while it only affects the
permanent load in small spans.
The extreme proof-strains habitually
placed on girder bridges to test them
are condemned; and an abstract is given
of the methods hitherto pursued by Ger-
! ber, Launhardt, and others for calculat-
! ing the effects of moving or " striking "
1 loads.
THE ATMOSPHERE CONSIDERED IN ITS GEOLOGICAL
RELATIONS.
By EDWARD T. HARDMAN, F.C.S., H.M. Geological Survey of Ireland.
From "The Quarterly Journal of Science."
The gaseous envelope which surrounds
our globe plays a very considerable part
in the chemical changes ever going on in
rock formations, whether actually at the
surface — as in what is called the
" weathering " of rocks — or in the less
apparent, but perhaps more powerful,
action carried on at greater depths,
whither the atmospheric gases are con-
veyed by the action of percolating water.
It has been shown by the experiments
of Prof. Rogers, as .well as by those of
Bischof and others, that perfectly pure
water has a very appreciable solvent
effect on rocks and minerals; and that
its power is immensely augmented, and
capability to produce even more moment-
ous alterations in the form of chemical
decomposition added, when it is charged
with carbonic acid, oxygen, nitric acid,
and other matters derived directly or in-
directly from the atmosphere.
While on the one hand, the influence
of the atmosphere disintegrates and
destroys rock-masses, on the other it is
mighty in building them up. Without
the small percentage of carbonic acid
contained in air — a quantity relatively
minute, but in the aggregate enormous
— there could be no vegetation. The
vegetable kingdom, which obtains its
supplies of carbon from those insignifi-
cant traces, would be wanting, and there
could be none of the coal-beds which
form such important members of our
rock-formations. This is a direct and
palpable case. But if we consider the
immense masses of limestones which
have been accumulated from those of the
Laurentian period, and for aught we
know before it, up to the coral reefs of
the present day, and which must owe
their being indirectly to carbonic acid
of former atmospheres, we shall have
some idea of the stupendous results at-
tained by very small means, provided
time enough be granted.
A drop of rain water absorbs a trace
of carbonic acid from the atmosphere,
falls on a rock containing lime in some
136
VAN nostrand's engineering magazine.
form, dissolves the lime as bicarbonate,
carries it down to the ocean, and finally
gives it up to become part of the skele-
ton of a coral or mollusc, which in its
turn may form a portion of an immense
mass of limestone rock.
The atmosphere mainly consists of a
mechanical mixture of oxygen and nitro-
gen; these, however, bear to each other
an almost constant proportion, any varia-
tions being extremely minute. The com-
position by volume is found to be as
follows :
Oxygen 20.80
Nitrogen 79.20
Carbonic acid,* 3 vols, to 10 vols, in
10,000 vols.
Ammonia, a trace; 0.1 to 135 vols, in
1,000,000.
Nitric and sulphuric acids, traces oc-
casionally.
The respective amounts of oxygen and
nitrogen do not vary to the extent of as
much as 1 per cent., even in exceptional
cases. Regnault's analyses of samples
of air collected in various parts of the
globe gave very close results, the per-
centage of oxygen being to all intents
and purposes identical, viz., 20.9 per
cent. Air collected by Sir James Ross
in the Arctic Regions did not differ in
this respect from that collected at Paris,
or at Ecuador in South America; the
very slight differences that have been
observed not exceeding those noticed in
air collected at the same place at differ-
ent times : and the same results have
been obtained from air collected at the
summit of Mont Blanc, and even from
that taken at a height of 21,000 feet by
Gay-Lussac during a balloon ascent.
There is, therefore, a marked uniformity
in aerial mixture under all * circum-
stances.f
It has not yet been explained how it is
that a mere mechanical mixture should
have this constant composition, but it is
certain that the gases are not chemically
combined —
* Strictly carbonic anhydride; but I shall use the less
scientific but more familiar term in this paper to desig-
nate it, in accordance with geological custom as regards
this gas. Indeed, in its geological relations it may be re-
garded as a true acid when dissolved in water.
t From some recent observations, by Boussingault and
Miller, it wou.d appear the amount of oxygen slightly
differs at various heights. Mendeleeff thinks Gay
Lussac's results are probably incorrect (Bull. Soc. Ghim.
[2], xxv., 394). However, we have hardly decisive in-
formation yet on this point.
1. Because the proportion of the con-
stituents bear no simple relation
to the atomic or combining weights
of those elements.
2. When they are mixed in the proper
quantities there is no contraction,
nor is there any evolution of heat,
and the mixture acts in every way
as air.
3. Water through which air is passed
dissolves the two gases in very
different proportions to those in
wjiich they are associated, the
oxygen being very soluble, while
the nitrogen is not taken up to
any notable extent.
CARBONIC ACID.
Although the bulk of the atmosphere
is made up of the two gases just referred
to, these do not take so active shares in
geological matters as the almost infini-
tesimal trace of carbonic acid present.
This, then, deserves the place of honor
in the following pages, and it will be
seen that there is a great deal to be said
about it. We shall, therefore, defer the
consideration of the behaviour of the
other constituents for a little while.
The amount of carbonic acid ranges
from about 3 to .10 volumes in 10,000
volumes of air, and the proportion varies
between these limits in different locali-
ties, owing to many modifying causes.
In the neighborhood of towns or cities it
will be much increased by the com-
bustion of fuel, the exhalations of animal
life, and the decay of organic matters.
In the vicinity of large forests, swamps,
and fens, vegetable decay will also aug-
ment it, though at the same time the
living vegetation there will help to re-
absorb it, or, to speak exactly, to decom-
pose it. Near volcanoes the air will be
more or less impregnated with it; and
from many mineral springs, and subter-
ranean caves and fissures, a very con-
siderable quantity of this gas is dis-
charged into the atmosphere. The per-
centage of carbonic acid also varies
slightly between day and night.
GEOLOGICAL EFFECTS.
So small a trace as even 10 in 10,000
— taking the maximum at only 0.1 per
cent. — certainly does not at first sight
seem capable of performing any very
great geological work ; but we must
GEOLOGICAL RELATIONS OF THE ATMOSPHERE.
137
recollect that the vast quantities of ex-
isting vegetation are entirely dependent'
on the carbon they obtain from the at-
mosphere, and the decay of vegetation,
and consequent liberation of carbonic
acid, has a very powerful effect in the
alteration or solution of rocks. How-
ever, the direct action of atmospheric
carbonic acid on rocks — both as a de-
structive and as a recuperative agent —
must be anything but small, even at the
present day. As to the latter, it is only
necessary to refer to the immense coral
reefs now being formed, while the wide-
spread deposits of ooze and mud over
the floors of the Atlantic and Pacific
are largely due to carbonic acid entrapped
by rain water and carried down into the
ocean. On the one hand, the carbonate
of lime previously conveyed by river
waters is held in solution, and kept in a
fit state for assimilation by marine or-
ganisms. On the other, the dead shells
while sinking through great depths are
attacked, forming, as Sir Wyville Thom-
son tells us, if the depth is not sufficient !
to give time for complete decomposition, '
a calcareous ooze; at greater depths the j
deep sea muds.* Thus a very great j
amount of the carbonate of lime in the j
ocean owes its existence entirely to at-
mospheric carbonic acid, either from the
direct action on calcareous rocks, wheth-
er old limestones or silicates, — or indi-
rectly through a series of changes where-
by carbonate of soda would be produced,
and this being brought into contact with
the chloride of lime so abundant in the
ocean, carbonate of lime would result.
There can be no question but that such
effects are going on extensively day by
day.
INFLUENCE OF VEGETATION.
If we follow the series of rock-meta-
morphisms, due to the simple absorption
of carbonic acid by a plant, the result
will be seen to be more than interesting.
The carbon is assimilated by the plant,
an equivalent of oxygen being exhaled.
The plant dies, and may become either a
part of a coal bed or may be separately
imbedded amongst layers of sediment of
* It now appears, however, that a considerable portion
of these muds is derived from the gradual disintegration
of pumice and other volcanic debris very widely spread
over the sea-bottom. See Mr. John Murray's paper on
the "Distribution of Volcanic Debris" (Proc. Koy. Soc
Edinb.). The result is still due, however, to the action of
carbonic acid dissolved in the ocean.
some kind. Slow decomposition will
now set in, sooner or later, and, if there
be a reducible compound near it, chemi-
cal changes result. Say the strata con-
tains sulphate of iron: this is reduced to
sulphide, commonly known as iron py-
rites, a very common mineral in coal
seams — as colliery owners know too well
— or in other strata where plants abound.
The reduction is effected by the carbon
of the plant abstracting the oxygen from
the sulphate, and the resulting carbonic
acid either is taken up by percolating
water, and penetrates farther into the
heart of the rock, effecting new changes,
and producing carbonates, or it finds its
way to the surface through some crevice
or by the aid of a mineral spring, and
once more mingles with the atmosphere,
to be perhaps again absorbed by vegeta-
tion, and pass through a round of similar
changes afresh. Carbonic acid exhala-
tions are very abundant at the surface of
the earth, and are in great part ascriba-
ble to the oxidation or decay of organic
matter which in the first instance de-
rived its carbon from the atmosphere.
The above case shows the result of
slow decomposition at great depths; but
similar effects are induced by the decay
of organic matter near or at the surface.
In swampy grounds, lagoons and deltas,
such as those of the Mississippi and the
Sunderbunds, the decay of organic mat-
ter must exercise a very powerful influ-
ence on the chemistry of the soils, rocks
and sediments with which the water
charged with the compounds formed dur-
ing the process of rotting comes in con-
tact. Peroxides, such as those of iron
and manganese, will be reduced to the
proto state, and will be rendered soluble
and carried away in solution, to be after
a while re-oxidized and deposited in such
masses as to be worth working as ores.
Silicates of soda, lime and magnesia will
be decomposed, and removed as carbon-
ates; and sulphates, which are usually
present in most waters, will be reduced
first to sulphides, and eventually decom-
posed with evolution of sulphuretted
hydrogen. Such a process as this may
be observed every autumn in the North
of Ireland during the maceration of the
flax plant, which is placed in pits filled
with water, and, being allowed to remain
for some weeks, the softer tissues are
rotted away, leaving the fibers fit for
138
van nostrand's engineering magazine.
manufacture. The stench of sulphuretted
hydrogen from the decomposing flax is
almost unbearable. Having analyzed
the mud which subsides to the bottom of
the flax-pits, I find that the reducing
power of the rotting tissues are as de-
scribed above. The clay in which the
pits are sunk contains nearly all the iron
present in the ferric condition when not
subject to the action of the plants, but
in the mud from the bottom there are
only proto-compounds, the iron mostly
as carbonate. Nor is there a trace of
peroxide of iron in the flax-water, but,
on the contrary, plenty of ferrous iron.
Clay -Ironstone. — After this fashion
must have been formed the clay-iron-
stones of the coal-measures. The great
swampy estuaries of that period may be
regarded as gigantic flax-pits; and the
rotting vegetation not only altered other
salts and compounds of iron to carbon-
ates, but prevented the oxidation of such
carbonate of iron as might have been
carried down in solution, until in course
of time it also was precipitated along
with the clayey sediments.
During such changes near the surface
a very large proportion of carbonic acid
is returned to the atmosphere. And that
there must be, and always has been, this
constant circulation of carbon between
the earth and the atmosphere is self-evi-
dent. What time it originated must be
beyond our ken, but, so far back as we
have any knowledge of, there are evi-
idences in the rocks of vegetable or ani-
mal life. And the decomposition of such
carbonaceous matters, whether at the
surface, immediately after death, or whilst
buried under a depth of strata, — as in
the case of coal-seams, — has always yield-
ed carbonic acid to the atmosphere. At
the same time the carbon returned in
this way falls far short of what has been
abstracted. But, as Bischof points out,
the carbon acts as a carrier of oxygen
between the mineral kingdom and the
air.
FORMERLY GREATER ABUNDANCE OF AT-
MOSPHERIC CARBONIC ACID.
It has long been considered probable
that in remote ages the proportion of
carbonic acid was greater than it now is,
more especially during the Carboniferous
Period. The remarkable luxuriance of
vegetation of a tropical fades during
that era, in every part of the globe, —
"even the polar regions, — indicates a very
warm climate universally, and it is also
thought to imply a much larger supply
of carbonic acid than is now noticeable
in the atmosphere. The rarity of warm-
blooded animals has been pointed to as a
corroboration of this view; but strictly
this is only negative evidence, the ab-
sence of fossil forms affording no proof
as to the non-existence in by-gone time of
animals of any particular type. How-
ever, a very curious fact bearing on the
question has resulted from Prof. Tyn-
dall's researches on radiant heat. It
appears that a very small addition of
carbonic acid to air renders it absorptive
and retentive of radiant heat, and a slight
increase in the percentage of carbonic
acid in the atmosphere would have a
very distinct result. The visible rays of
the sun could pass through the atmos-%
phere to the earth; but the radiant heat
from the earth, instead of being dissipa-
ted into space, would be imprisoned by
the atmosphere, which would thus form
a warm envelope around the earth, con-
verting it in fact into an immense green-
house. The glass roof of a conservatory
acts in precisely the same way: it per-
mits the solar rays to penetrate freely,
but absorbs and cuts off the escape of
the radiant heat, and the interior tempera-
ture is thereby rendered tropical. Grant-
ing, then, the former abundance of
carbonic acid, the extreme richness of the
carboniferous vegetation, its tropical
character and wide distribution are very
fairly accounted for. I shall show pres-
ently that there are other grounds for
the supposition that the carbonic acid is
now much less than it has been in these
far back periods; nor is it to be consid-
ered that it reached its maximum even
in the carboniferous age. It is true that
the earlier formations afford nothing like
such a superabundance of fossil plants;
but this has been well accounted for by
Dr. Sterry Hunt. He has shown that
the vast amount of chemical action that
has taken place in the reduction and
accumulation of the metalliferous depos-
its of the older Palaeozoic rocks will
readily account for the scarcity of fossil
vegetation in those rocks. To the decay
of plants and the reducing action of the
resulting carbonic acid those deposits
must be in great measure attributed; and
GEOLOGICAL RELATIONS OE THE ATMOSPHERE.
139
their existence proves that an abundant
flora flourished. The manner in which
this chemical action takes place will be
explained further on. I shall just quote
Dr. Hunt's words on this point: — "Where
are the evidences of the organic material
which was required to produce the vast
beds of iron-ore found in the ancient
crystalline rocks. I answer that the
organic matter was, in most cases, entire-
ly consumed in producing these great
results, and that it was the large propor-
tion of iron diffused in the soils and
waters of these early times which not
only rendered possible the accumulation
of such great beds of ore, but oxidized
and destroyed the organic matters which
in later ages appear in coals, lignites,
pyroschists, and bitumens. Some of the
carbon of these early times is, however,
still preserved as graphite, and it would
be possible to calculate how much car-
bonaceous material was consumed in the
formation of the great iron -ore beds of
the older rocks, and to determine of how
much coal or lignite they are the equiva-
lents." *
If we also reflect that the enormous
quantities of lime-stones which are found
in the older formations have been largely
dependent on the carbonic acid of the
atmosphere — in effect, the further we
retrograde towards a primitive condition
of things the more directly such carbonic
acid must have come into requisition for
such purposes, as there would be the less
of it stored up in rocks, to be re-utilized
as at the present day, when much of the
carbonate of lime in waters is obtained
by the disintegration of pre-existing lime-
stones— and remember also the carbon
that was required for the teeming animal
life of ancient times, we shall see that
there could have been no lack of carbonic
acid; and it becomes a matter of small
difficulty to accept the theory that a
retrogressively greater proportion of
carbonic acid gradually leads back to a
primitive atmosphere in which that gas
— as well as perhaps other gaseous acids,
such as hydrochloric acid — was very
abundant.
In regard to this question as to the
increase or decrease of carbonic acid, a
variety of very interesting points sug-
gest themselves, and the facts almost al-
* " On the Origin of Metalliferous Deposits."- -Chem.
and Geological Essays, p. 229.
together seem to range themselves on the
side of a progressive decrease of car-
bonic acid. It seems certain that the
amount of carbon stored up in the re-
cesses of the earth very far exceeds that
of the entire quantity combined as car-
bonic acid in the air. It is true that
Liebig supposed the carbon so combined,
which he calculated to reach 2800 bil-
lions of pounds, equal to about 1,250,-
000,000,000 tons, — figures and tons will
probably aid in a better conception of
this enormous weight, — to be far in ex-
cess of all the carbon stored up in coal-
beds, and in plants on and in the globe.
But this will hardly be subscribed to
when we remember that the coal of the
British Isles alone, as estimated by the
late Coal Commission, is about 1 95,000,-
000,000 tons (I have added about a third
for waste, &c, deducted in the original
estimate). The carbon in this will weigh
about 146,000,000,000 tons, taking an
average of eighty per cent. But this
was only calculated for coals fit for use,
of not less than one foot thickness,
lying at no greater depth than 4000 feet.
Now if we include all the coal of inferior
quality, of less than one foot thick, and
at greater depths than 4000 feet, and
then throw into the balance the enor-
mous supplies of coal of the rest of the
world and of the older and newer forma-
tions, not to speak of the highly 'car-
bonaceous shales, slates, schists, and clay
ironstones, I think — even taking only
this branch of the subject — we should
rather be led to agree with Bischof,
who, on the other hand, calculates that
there is at least 6620 times as much car-
bon in the earth as Liebig has estimated
for the atmosphere;* and Bischof s cal-
culation is based on the very moderate
assumption that the average proportion
of carbon in all rocks is at least 0.1 per
cent., which he considers — and no doubt
justly — must fall far short of the real
amount. This being so, it would cer-
tainly appear that there has been more
carbon accumulated in the earth than
has been restored to the atmosphere by
decomposition, and that therefore the
quantity of carbonic acid in the air has,
been gradually lessening from remote^
periods up to the present time. This
* Bischof. Chem. Geology, vol. i., p. 204. Dr. Sterry
Hunt has also estimated the amount of carbon secreted
in the earth as far beyond that contained in the preseat
atmosphere,
140
VAN NOSTRAND'S ENGINEERING MAGAZINE.
appears anything but improbable, re-
membering the arguments already no-
ticed in favor of the supposed highly
carbonated atmosphere of the carboni-
ferous period; and although the calcu-
lations leading to such a conclusion are
necessarily based on very imperfect
data, it may be safely affirmed, at least,
that such a state of affairs is not only
possible, but probable.
In these calculations we are not only
to consider the carbon of the vegetable
kingdom, for it will be obvious that any
animal carbon which may remain in
rocks is also more or less directly
derived from the carbonic acid of the
atmosphere. Taking the extreme case
of the Carnivora, it is clear that they
must ultimately depend on the air for
their supplies of flesh-forming material.
Say a tiger dines off a cow; the carbon
,and nitrogen of her flesh have been ob-
tained from vegetation, which in turn
extracted them from the air; so that we
have a kind of physiological " House
that Jack built." "This is the Tiger
that ate the Cow that devoured the
Grass that absorbed the Carbon," &c.
Viewed in this way it seems that " living
on air " is a more substantial kind of ex-
istence than has usually been supposed.
Now this which is true of the higher
animals applies equally with regard to
lower forms. There will be a vegetarian
somewhere to fall a prey to a carnivor-
ous marauder, who in his turn may be
the victim of a stronger individual; and
the successive appropriations may go
through any number of steps. Thus the
carbon and nitrogen of forms of animal
life now fossil have been also, derived
from the atmosphere. We do not find
much, if indeed any, of this carbon in its
original form now, or directly traceable
to animal agency, because highly nitro-
genous organic substances decay very
rapidly, but it is not unlikely that their
results are to be seen in carbonaceous
and bituminous shales, and oleiferous
rocks such as those in the neighborhood
of petroleum springs; for, as Dr. Sterry
Hunt remarks, since animal tissues con-
. tain the elements of" cellulose, plus water
and ammonia, they may give rise to
similar hydrocarbonaceous bodies to
those derived from vegetable sub-
stances.*
In many cases, also, the decomposition
of these animal tissues would result in
the formation of carbonates, so that on
the whole there must be, through this
source, a vast quantity of carbon — origi-
nally drawn from the air — locked up in
the crust of the earth. And to all must
be added the immense amount of carbon
combined as carbonate of lime due to the
direct solvent action of atmospheric
water on calcareous rocks and minerals.
If we add all this to the vegetable carbon
already considered, there can hardly be
a question but that the amount of carbon
abstracted from the atmosphere and hid-
den away in our globe very, very far,
exceeds the proportion present in the air
of this age. If this be granted — and I
cannot see any possible evasion of it — we
must admit that the more ancient atmos-
pheres contained far more carbonic
acid than that which now envelopes us,
and must renounce the doctrine of Uni-
formity in this connection at any rate.
ORIGIN OF CARBONIC ACID.
Having got so far, we are naturally
led to inquire as to the origin of the car-
bonic acid in the first instance. Carbon
is so thoroughly associated in our minds
with organic matter, or in fact with life,
that it is difficult to conceive the possi-
bility of its existence in an azoic world,
and the difficulty is aggravated by the
recollection that the earth must have
been at the beginning in a state of incan-
descence, not to go further and say a
gaseous condition. However, under the
influence of extreme heat, many elements
are isolated which at lower degrees of
temperature — but still very great — com-
bine and form chemical compounds.
For example, hydrogen and oxygen at a
high temperature unite to form water,
but at a still higher are again dissocia-
ted, and we know that hydrogen exists
in a state of incandescence, not combus-
tion, in the sun's photosphere.f Similarly
free carbon might have been one of the
gaseous constituents of the earth in its
nebulous phase, J and as the temperature
lowered might have been consumed, or
united with oxygen, and gone to form
part of the primeval atmosphere. In
* Chein. and Geol. Essays. "On Bitumens and Pyro-
schists," p. 179.
t Prof. Henry Draper has just announced the discovery
of oxygen in the sun. Nature, August 30, 1874.
t According to Mr J. Lawrence Smith, carbon in the
gaseous form is spectroscopically manifest in the attenu-
ated matter of comets. Am. Journ. Sci., June, 1876.
GEOLOGICAL RELATIONS OF THE ATMOSPHERE.
141
this way all the carbon now in the crust
of the earth would necessarily have been
at first confined to the atmosphere. Then
when rains began to fall, the carbonic
acid, being carried down upon the earth,
would soon decompose the silicates which
must have resulted from the cooling
down of the original heated mass; car-
bonates would be formed and carried
down into the primitive oceans, and
clayey residues would be left behind.
In course of time, when vegetable and
animal life had made their debut, the
withdrawal of the carbonic acid from the
air must have proceeded much more rap-
idly, and the atmosphere gradually
cleared to such a condition as to permit
of the existence of air-breathing animals.
It may be here remarked that the very
gradual introduction, in more . recent
periods, of warm-blooded beings, would
also coincide with the hypothesis of the
originally highly mephitic state of the
atmosphere.
CARBONIC ACID NOW INCREASING OR DE-
CREASING ?
An important question now arises — Is
the amount of carbonic acid increasing
or decreasing, and what may the result
be in either case ? To begin with the
last part of the question: — Any consider-
able difference one way or the other must
result in a diminution of animal life: in
its higher forms in the former event, in
all divisions in the latter. Beyond a cer-
tain proportion very little above the
ordinary standard — at most ten times,
equal to about five vols, in 1000,* or 0.5
per cent ! — carbonic acid in air becomes
a deadly poison to all warm-blooded ani-
mals. On the other hand, a diminution
in the percentage of carbonic acid would
tell even more severely. Vegetable life
would languish, graminivorous animals
would eventually have nothing to eat,
and, finally, the Carnivora, being obliged
to prey upon each other, would of course
become extinct. And this would be ap-
plicable to all divisions of the animal
kingdom. The result would be a com-
pletely barren and desolate planet, per-
haps in some degree resembling the moon.
Doubtless that planet has passed through
phases of existence alike to those which
have obtained upon the earth; and Mr.
* Watts, Chem. Diet., 1862, vol. i., p. 438.
Proctorf is of opinion that the moon
certainly had originally an atmosphere,
which is now either altogether absent or
is attenuated to an extreme degree. It
can well be imagined that this result, and
its consequent azoic addition, has been
brought about by some such absorption
of the constituents of the moon's atmos-
phere as that which I have endeavored
to sketch out above as regards the earth.
Ppobable Withdrawal of Oxygen.
— It may seem a little paradoxical that
such dire effects would more immediately
follow the withdrawal of a poisonous
gap, and that the latter is on the whole
more important to the continuance of
life than oxygen gas, which is almost in-
separable from our ideas of existence;
but it is undeniable that such would be
the case. The blood requires to be
oxygenated, but in the absence of carbon
there would-be no blood at all. All this
leads us to another point. The disap-
pearance of carbonic acid must be fol-
lowed after a period by the withdrawal
of oxygen itself. It would gradually be
carried by water into the interior of the
earth, from which it could make no re-
turn, for it would be seized upon by
compounds capable of oxidation, and its
retreat in the form of carbonic acid
would have been cut off.
As to the first part of the question,
however, we have as yet no data for its
solution. There are several means by
which carbonic acid is supplied to the air,
and many by which it is removed; but
we are not in a position to determine on
which side is the predominance, or
whether there is at present a balance of
power. The principal sources of increase
are
1. Volcanic and other subterranean
exhalations.
2. Respiration of animals.
3. Combustion of fuel, &c.
Respecting this last it should be pointed
out that we are now restoring to the
atmosphere some of the vast quantities
of carbonic acid abstracted from it dur-
ing the Carboniferous period, and im-
prisoned for ages in the interior of the
earth in the forms of coal and clay-iron-
stone. Perchance by the time we have
made an end of our supplies of coal a
t Quart. Journ. Science, July, 1874. " On the Past
History of our Moon."
142
VAN NOSTKAND'S ENGINEERING MAGAZINE.
very sensible difference will have been
effected in our atmosphere.
The absorption of the carbonic acid is
brought about thus:
1. By vegetation, as already explained.
2. By the agency of marine organisms
which secrete carbonate of lime.
3. By the direct action of atmospheric
carbonic acid upon rocks, result-
ing in the formation of carbonates.
How far these antagonistic processes
check each other cannot be conjectured.
In order to arrive at any conclusion on
the matter we should require to compare
trustworthy analyses of air taken at fre-
quent intervals during some thousands
of years at least. We have yet no re-'
corded analyses of it older than forty or
fifty years. Probably in the remote
future information will have been accu-
mulated sufficiently to allow of the solu-
tion of the problem; and perhaps in
those far distant times a Royal Commis-
sion, or some such form of Public In-
quiry, will be solemnly convened to
deliberate as to the possible duration of
" Our Carbonic Acid Supplies." But
should a necessity ever arise, it is com-
forting to reflect that it is not likely to
occur until some ages after the traveled
New Zealander has been gathered to his
fathers, and even the very sites of Auck-
land and Otago perhaps long a subject
of curious speculation amongst Central
African savants. I say it is comforting
to take this to heart in these days of
sensational cosmogony, when one day we
are threatened with destruction from
the sweep of a comet's tail, and the next
an unfavorable eruption of sun-spots
may entail unheard-of miseries upon us.
All the information we are in possession
of goes to show that the trifling changes
that are now observed in the condition
of the atmosphere would perhaps require
a continuance throughout many millions
of years before making themselves dis-
agreeably apparent.
GEOLOGICAL INFLUENCE OF OXYGEN.
This comes next in importance as a
geological agent.* I have dwelt first
upon the results wrought by the carbonic
acid, because the work done by it is
immensely greater in proportion to its
* The amount of oxygen in the atmosphere is about
two trillions of pounds (Bischof, op. cit., i., 204), equal to
about 892,857,000,000,000 tons.
amount. But oxygen also has its mis-
sion. Percolating the rocks, dissolved
in rain-water, which is able to absorb a
very large quantity of it, it quickly
reacts on all oxidizable substances. Car-
bonates and proto-salts are converted to
peroxides ; sulphides are changed in sul-
phates, and sometimes this is accom-
panied by the production of double salts,
such as alums. A familiar instance may
be referred to as occurring in the spoil
banks of coal-pits, where quantities of
aluminous shales, with refuse coal con-
taining iron pyrites, are heaped up to-
gether and exposed to the influence of
the weather. The oxidation of the iron
pyrites results in sulphate of iron, and
the sulphuric acid so formed — reacting
on the alumina, potash, etc., of the
shales — forms a more or less complex
alum, which may be observed in small
stellate crystals between the laminse of
the shales. Alum slates and earths are
very common, and all owe their origin to
the oxidation of iron pyrites, or some
other sulphide, under circumstances akin
the above.
ORES AND METALLIFEROUS DEPOSITS.
The peroxides of iron and manganese
are of considerable importance, both
commercially and from a scientific point
of view. In many cases the formation
may be traced directly to the action of
atmospheric oxygen. In other instances
this action is but veiled by a series of
complications. Many valuable deposits
of iron and manganese are formed in
cavities of rocks through the means of
water containing carbonic acid and oxy-
gen. The first dissolves the minerals as
bicarbonates ; then, the excess of car-
bonic acid escaping as opportunity per-
mits in open fissures, they are oxidized,
and deposited at once in an insoluble
form, while such other carbonates as
happen to be in solution, and which —
like lime, magnesia, and the alkalies —
have a stronger affinity for carbonic
acid than for oxygen, are carried away.
By such a process as this, immense
beds of limonite have been deposited,
and the liberated carbonic acid restored
to the atmosphere. Bog iron-ores and
the well-known lake iron-ore deposits of
Sweden, are cases in point. Some of
these deposits are assisted by organic
agency, some of the Diatomaceas — Gal-
GEOLOGICAL RELATIONS OF THE ATMOSPHERE.
143
lionella in particular— being very active
in this way ; but they are only accessory
aids, the real work being due to chemi-
cal reactions between carbonic acid,
oxygen, and soils or rocks. The exten-
sive beds of hematite associated with
the Antrim basalts, are unquestionably
lake-deposits, as Prof. Hull has sug-
gested, and must be due also to the
reciprocal chemical action of the car-
bonic acid and oxygen from the atmos-
phere. These beds are now intercalated
between the sheets of basalt, and some-
times reach a considerable thickness, con-
sisting of beds of rich ore, poorer ore,
and " lithomarge," which is a highly fer-
ruginous clay. Prof. Hull considers
that all these were deposited in a large
lake or series of lakes. Assuming this,
the modus operandi was probably this :
The highly ferruginous basalt forming
the shores of these lakes being subject
to the action of atmospheric water, the
iron existing as proto-silicate in the
augitic rock, was dissolved out as car-
bonate and carried into the lake. The
excess of carbonic acid then escaping,
oxidation ensued, as in the case already
referred to, and the iron was precipitated
as a hydrated peroxide. At the same
time fine sedimentary aluminous matter
was also carried down and deposited,
and, according as the amount of this
was greater or less, a bed of lithomarge
or workable ore was laid down. A
fresh volcanic outburst eventually tak-
ing place, the lakes were covered in, and
the ore bed preserved from denudation.
The ore must have been precipitated
in the hydrated state, and the water of
combination was doubtless afterwards
given off spontaneously, in the same way
as by hydrate of alumina and the hy-
drated forms of silica. There is indeed
considerable analogy between the hema-
tites and the colloid forms of quartz. It
is only necessary to compare these piso-
litic and botryoidal iron-ores with the
calcedonys to see this, and the compari-
son would be in favor of the aqueous
origin of such iron-ores were fresh proof
needed.
It will be obvious that the reactions
sketched out above with regard to iron-
ores and compounds, applies equally to
all other minerals capable of being oxi-
dized or reduced. Copper pyrites, for
instance, is often oxidized to sulphate,
and the carbonate altered to oxide just
in the same manner.
ANTAGONISTIC ACTION OF CARBONIC ACID
AND OXYGEN.
Clearly, then, the carbon and oxygen
derived from the atmosphere sustain an-
tagonistic parts in their action on rocks
and minerals. They are perpetually
warring the one against the other, and
thus keeping a circulation between the
earth and the air. The carbon reduces
the oxides whenever it encounters them,
and the oxygen replaces the carbonic
acid of carbonates with the same invete-
racy. The combined effects of these
elements in geological transformations is
extraordinary when we come to reflect
on it. Regarded from an utilitarian
point of view, to them we owe probably
every metalliferous deposit of value in
the world. I have shown how a highly
ferruginous rock, such as basalt, contain-
ing proto-salts of iron, which are soluble
in carbonic acid, might be acted on di-
rectly by that acid from the atmosphere.
But there are cases where insoluble com-
pounds of iron in small quantity, locked
up in rocks, are, by the reducing action
of the carbon of decaying vegetation,
liberated, and finally accumulated in such
quantities as to be of commercial value.
Soils and clays contain small portions of
per-oxide of iron, which is insoluble.
The decay of vegetation or other organic
matter robs this of oxygen, giving rise
to carbonic acid. The resulting protox-
ide is soluble in water containing carbon-
ic acid, or other organic acids, and is
carried down into lakes or fissures, where,
again absorbing oxygen, it forms beds or
veins of hematite.
While insoluble oxides are rendered
soluble and allowed to accumulate in
this way, soluble sulphates are reduced
to insoluble sulphides, — iron pyrites,
copper pyrites, zinc blende, galena, &c.}
— and, as Sterry Hunt puts it, " removed
from the terrestrial circulation," for at
time at least. Such are the processes to
which many metalliferous deposits are
due.
Another result of the opposition of
these two atmospheric gases is the defer-
tilizing of soils, and consequent failure
of vegetation. An ordinary fertile natu-
ral soil contains, amongst other things,
silicates of alumina, lime, potash, and
144
VAN NOSTRAND'S ENGINEERING MAGAZINE.
soda, with some peroxide of iron. The
silicates of lime and soda will be decom-
posed by carbonic acid, and the bases
removed as corbonates. The potash sili-
cate is also decomposed, and a part of the
potash removed by aquatic plants under
favorable circumstances, in marshy
places, &c, — conditions under which the
vegetation of the Coal era flourished,—
and the ferric oxide is reduced to the
ferrous state by the deoxidizing influence
of rotting vegetation. This having oc-
curred, the roots of plants are for a- time
debarred from any access of oxygen, for
any that permeates the soil will be im-
mediately siezed on by as much of the
proto-compound of iron as has not been
carried off in its soluble state, and this is
again converted to the higher condition;
and these changes continue until they
result in the total barrenness of the soil
and its ultimate conversion into a hydrous
silicate of alumina, almost entirely free
from iron, such as we are acquainted with
in the fire-clays of the coal-measures —
those ancient soils on which the vegeta-
tion now forming our coal-seams once
grew.*
AMMONIA AND ITS COMPOUNDS.
Ammonia exists in the air chiefly in
the form of carbonate of ammonia, but
the quantity, whilst always small, appears
to vary greatly, and it is not positively
ascertained whether the variation is to
be ascribed to natural causes, or ought
to be referred to the difficulty of accurate
analysis when such small quantities have
to be dealt with. It is quite possible,
however, that the variability is natural.
The minimum recorded is 0.1 part of car-
bonate of ammonium in one million, of
air ; the maximum is 135 parts.f Rain-
water, hail, snow, and dew contain ap-
preciable quantities of ammoniacal salts,
and in rain from thunder-showers the
ammonia is combined as nitrate, the effect
of the electric discharge being to oxidize
a portion of the nitrogen of the air to
• to nitric acid. J
* It is obvious that this only applies to natural soils,
since the agriculturist by breaking up the ground affords
a supply of oxygen much in excess of what is absorbed
by the oxidizable matter present.
t Watts, Chem. Diet., p. 439. P. Truchot finds that the
amount of ammonia varies with the altitude. At Cler-
mont-Ferrand, 395 metres above sea-level, the quantities
were 0.93 m.grm. to 2.79 m.grm?. in a cubic metre of air,
—according as the day was clear or dull, — whilst at Pic de
Sancy, 1884 metres, it amounted to 5.27 and 5.55 m.grms.
under the game conditions. Comptes Rendus, lxxvii.,
1159—1161.
t Liebig found that of seventy-seven specimens of rain-
The atmospheric ammonia is not with-
out its effect on vegetation. It is certain
that plants grown in air perfectly free
from ammonia never flourish to the same
extent as those surrounded by an atmos-
phere containing some of it; and the ex-
periments of Boussingault, Lawes and
Gilbert— borne out as they are by those
of Stockhart, Peters and Sachs, and
lately by the very conclusive researches of
Shlcesing* and A. Mayerf — show that at
least a considerable part of, if not all, the
nitrogen of plants is derived from this
source. Now the geological connection
of this is at once plain, for the decompo-
sition of nitrogenous matter such as
plants, in rocks, may lead partly to the
formation of nitrates, or, by the evolution
of nitrogen and ammonia in volcanic
regions, give rise to other minerals, as I
shall show presently.
Occasionally the ammonia is absorbed
directly from the air by surface mineral
matter, as in the case of the volcanic
earth of the Solfatara of Puzzuoli. S. de
LucaJ tells us that this contains a quan-
tity of sulphur and arsenic which under
the influence of air and moisture form
acids, and at once, combine with the
atmospheric ammonia. But it is to the
decay of vegetation that the vast major-
ity of the nitrogen compounds which are
met with, either as minerals or as vol-
canic emanations, are due, and in what-
sver state the nitrogen was originally
absorbed — whether in the free state or as
ammonia— it cannot be doubted that all
the nitrogen compounds contained in the
earth, as it now exists, are traceable en-
tirely to past and present atmospheres.
The nitrogenous compounds so ob-
tained are themselves subject to an end-
less variety of changes, in which the
gases already described bear no unimport-
ant parts— reducing and oxidizing; and
these changes, or the effect of heat, may
result in a renewed evolution of ammo-
nia to the atmosphere.
Under such circumstances occasionally
the ammonia, instead of escaping freely
water, seventeen, collected during thunder-storms, con-
tained nitric acid combined with lime and ammonia. Of
the remaining sixty but two contained traces of it. —
Bischof, op. cit., i., p. 214. According to Bottger, The in-
duction spark passed through moist air gives nitrogen
peroxide and ozone, but in dry air gives nitrous fumes.—
Chem. Centr. (1873), 497. Doubtless similar results f oilow
discharges of natural electricity.
* Comptes Rendus, lxxviii., 1700.
tDeut. Chem. Ges. Ber., vi., 1404- -1413, and Landw.
Versuchs. Stat., xvii., 329.
t Comptes Rendus, lxxx., 674.
GEOLOGICAL RELATIONS OF THE ATMOSPHERE.
145
SULPHURIC AND SULPHUROUS ACIDS.
The exceedingly minute traces of these
acids make but a slight effect on rocks
when compared with the gases already
touched upon. That they are not alto-
into the air, meets with hydrochloric as , the nitrogen has been originally drawn
in the depth of volcanoes, and combining from that source. We may fitly conclude
with it is evolved as chloride of ammon- this part of the subject with the mention
ium (sal-ammoniac), which is condensed of the native sulphate of ammonium
on meeting with the cooler external air. [ Mascagnine, of which it may be said that
This mineral is often met with in large every constituent could have been ob-
quantity, so much so, indeed, as to be of tained from the atmosphere.
commercial value. Thus during the |
eruption of Vesuvius in 1794 great quan- i nitrogen.
tities of this salt were evolved, and it ! It is obvious that much of what has
was collected by the peasantry ; and been said regarding ammonia will apply
Hecla in 1845 yielded very profitable to nitrogen, but on the whole the latter
supplies of it. In the vapours of the in its free state appears to have but little
Solfatara, at Puzzuoli, it is also met with, influence as a geological agent.
and it is found mixed with sulphur and
other matters in the crater of Vulcano,
where it is now being largely collected,*
and in considerable quantity at Etna.
Then the volcanoes of Kutsche and Tur-
fan, in Central Asia, afford such large
supplies that it has been a very valua- j gether inert may be taken for granted,
ble article of commerce. f I but both their absorption and re-evolu-
Prof. Judd is at loss to explain the I tion are of a local nature, being chiefly
production of those large quantities of ; apparent in the neighborhood of large
sal-ammoniac, unless on Daubeny's sup- towns and about volcanic regions. They
position that nitrogen under the influ- may be " withdrawn from circulation "
ence of heat is unusually active; but the j as sulphates and sulphides, and be re-
matter is readily accounted for thus: — (turned in their original state, or deconi-
The decomposition of nitrogenous organic posed into sulphur or sulphuretted
matter at all times produces ammonia, I hydrogen,
but especially so under the influence of
heat (a familiar instance in the manufac- VARIATI0XS 0F atmospheric pressure.
ture of coal-gas). That a sufficiency of | These cannot but have an appreciable
such organic matter exists in the rocks . effect on certain classes of geological
through which these volcanoes have burst j phenomena. The emanations of gases
is undoubted, and the ammonia evolved from the interior of the earth are influ-
combines with avidity with the hydro- enced in some degree. It is well known
chloric acid]; also given out in volcanic j that explosions in coal-mines sometimes
emanations. I follow a sudden fall of the barometer,
Quite lately a new mineral has been j which can be well understood on compar-
discovered incrusting the recent lava | ing the pressure corresponding to differ-
both of Etna and Vesuvius. This is a
nitride of iron named " Siderazote " by
its discoverer, Silvestri,|| who considers it
is due to the decomposition of ammonium
chloride by heat in the presence of fer-
ruginous lavas; and although we may
not quite accept his theory that the am-
monium chloride is formed by the ab-
sorption of nitrogen direct from the
atmosphere by the lava, it is certain that
ent barometric heights.
Barometer at 2S inches.
29 "
31
Atmospheric pressure 13,70 lbs.
" 14,19 "
" " 14.6S "
" " 15,17 "
*J. W. Judd, "On Volcanoes," Geol. Mag., Dec. 2,
vol. ii., p. 113.
t Bischof, op. cit., i., 212—213.
t The formatiou of white fumes of ammonium chloride
when a glass rod dipped in ammonia is brought near hy-
drochloric acid will occur to chemical readers.
II •' The Occurrence of Nitride of Iron amongst the Fu-
marole Products of Etna, and its Artificial Preparation."
Orazio Silvestri, Gazetta, Chim. Ital., v., 301—307. Pogg.
Ann., clvii;, 165—172.
Vol. XIX.— No. 2—10
It is usual to refer to the atmospheric
pressure as about fifteen pounds on the
square inch, but the above table shows
that a considerable variation makes itself
felt within the barometrical range. This
must not only control evolution of gases
from coal-seams, but also exhalations
from open grottoes and caves, mineral
springs both thermal and otherwise, and
probably from intermittent active volca-
noes, such as Stromboli, where the peri-
odical explosion of gases is an important
146
TAN NO STRAND'S ENGINEERING MAGAZINE.
phenomenon. With regard to this Mr.
Judd says " that the barometrical condi-
tion of the atmosphere must exercise a
powerful influence on such a series of
operations as are seen to be going on
within the crater of Stromboli, few, prob-
ably would be bold enough to deny."
It appears " that the more violent states
of activity .... coincide with the
winter seasons and stormy weather, and
its periods of comparative repose occur
during the calms of summer, is estab-
lished not only by the universal testi-
mony of the inhabitants, but ....
by the actual observations of many com-
petent authorities." It is hardly neces-
sary to point out that during stormy and
wintry weather the barometer is mostly
low, while the contrary is the case dur-
ing summer time and calms.
It is not impossible that similar antag-
onism between outward and inward
pressure may affect the working of many
other vents, such as the Solfatara of
[Naples, and mud-volcanoes, such as those
of Sicily, Transylvania, &c. ; and that
such variations may have no inconsider-
able results, both as regards the chemical
and cosmical effects of volcanic action.
And now, reviewing the preceding
notes, it will be seen what an all-power-
ful geological agent the atmosphere we
breathe is. Without its aid we should
know never a stratified formation. The
earth would simply form a ball of truly
primitive rock, resulting from the cooling
down of the original nebulous mass set
apart for our globe, the only variation in
which primeval and perennial crust being
that of the different strata of higher
specific gravity towards the interior. We
should have no coal, no metalliferous de-
posits, no rivers or seas, and no rain,—
consequently no denudation by "Rain
and Rivers,"— for the vapor of water
could not ascend into empty space. We
should have — « — but, last and worst of all,
there would be no " we." Life would be
impossible, and the earth would finally
degenerate into a
"pale-faced moon."
That this is probably her ultimate mission
cannot be denied. The only consolation
is that owing to her larger size, and there-
fore slower rate of cooling than the moon,
she will have gone through a somewhat
more extended geological course. There
is undoubtedly a very intimate connec-
tion between secular cooling and with-
drawal of atmosphere, for the cooler the
interior the smaller will be the return of
gaseous elements to the surfaces; and
probably before Saturn and Jupiter have
cooled down to a habitable temperature,
the senescent earth will roll through
space — cold, void and airless. Sooner or
later nothing is more certain than that
" to this favor she must come."
MAXIMUM STRESSES IN FRAMED BRIDGES.
By Prof. WM. CAIN, A.M., C.E.
Contributed to Van Nostrand's Magazine.
II.
51. The weights just found are in ex-
cess of average practice. This is partly
because we assumed an engine weighing
84000 lbs. on drivers in space of twelve
feet, the total weight of engine and
tender, covering fifty feet, being taken
at 160000 lbs., whereas a common speci-
fication gives the live load as 60000 lbs.
on twelve feet, the engine and tender
weighing 130000 lbs. The car loads
ordinarily assumed are from 2000 to 2240
lbs. per foot. We have also used smaller
unit strains than usual for some bridge
members. Since the Ashtabula accident
it was proposed to the Ohio Legislature
to assume for bridge computations a live
load of two locomotives and tenders, the
locomotives weighing 91200 lbs. on 12^
wheel base, followed by cars weighing
2250 lbs. per foot of track.
In the Keystone Bridge Company's
"Album" p. 22, we read; "For main
lines of traffic, it is not considered pru-
dent to assume less than 40 tons in a
span of twelve feet, — stringers spanning
over 12 feet should be sufficiently strong
MAXIMUM STRESSES IN FRAMED BRIDGES.
147
to carry 1| tons per foot for each addi-
tional foot." (The 2000 lbs. ton is meant.)
Considering the fact that engines are
built with us weiging 100000 lbs. on J 9
feet, it would seem that, for roads that
use such engines, the live load assumed,
art. 14, is certainly not too great. For
secondary lines a less weight might be
assumed, if the road is to continue
secondary.
Mr. C. Graham Smith, in a paper read be-
fore the Liverpool Enginering Society, of
which he was President, June 20, 1877, and re-
published in the "Engineering News," Chica-
go, says:
"Mr. Benjamin Baker has conclusively
proved, in his admirable little work on ' Long
Span Railway Bridges ' that there are many
circumstances, such as badly maintained per-
manent way, inclined cylinders, and un-
balanced portions of the mechanism of loco-
motives, together with great weight and length
of engines, combined with short wheel base,
which will at times render the effective load on
one axle equivalent to thirty tons ....
" With shallow cross girders, oscillations are
set up by heavy continuous traffic which will
soon shake loose rivets and bolts and perhaps
the connections with the main girders ....
" Here is an actual example, recorded in the
before mentioned 'Long Span Railway
Bridges. ' The platform of the railway bridge
over the Regent's Canal was constructed, owing
to local circumstances, with cross girders only
8 inches deep and 14 feet 6 inches span.
With a view of compensating as much as possi-
ble for want of depth, longitudinal stiffening
above, is greater than usual perhaps, as
it is not generally customary to find the
maximum strain in the chords as above.
If two opposing trains meet in the cen-
ter of the span or elsewhere on the span,
the strains induced would be greater
than given by our formulae if the center
driving wheels of the two locomotives
are less than 50 feet distant. The con-
ditions, included in the formula for
chords, are that cars may precede and
follow engines 50 feet apart, a condition
that certainly can be realized in practice.
In fact the end panels would be strained
nearly as given by our formula, with
engines in front as usual.
The maximum chord strains thus found
will however be more rarely felt than
the max. web strains, for the latter are
caused by every passage of the supposed
train — engines in front — whilst the former
are only felt when the engines are in the
midst of a train. Let us conceive the
whole live load uniformly distributed
over the bridge; the total panel weight
then would be 35666 lbs., which substi-
tute for P in the formula, art. 39, and
make E=o. We have,
Yl
cn = tn= -j (N—n) n — 10600 (N—n)n
On computing the various chord
girders 18 inches deep were placed at a distance I strains from this formula and comparing
with the max. strains previously found,
we shall find that we must add 10 per
cent, to strains in first two end panels,
9 per cent, for next two panels and 8
and 7 per cent, to the strains in panels
next the center, in order that the strains
of 2 feet 3 inches from the outer edge of each
rail; each cross girder was also well secured
by tee iron and gusset plates to the main gird-
ers. The bridge, notwithstanding that with
15 tons to one axle, it was so designed that the
iron should not be strained more than 4 tons
per square inch, completely gave away in four
years. Mr Baker attributes the failure to the ^ f d j th max# strains#
employment of a 4o ton engine, the wheel base
of which was 14 feet; the ends consequently
overhung very much, which would greatly
assist in producing oscillations and other un-
desirable consequences."
Similar facts have been recorded in
this country, though the use of trucks
causes our locomotives to run much
The use of
50
steadier than English ones,
deep gk'ders is then advisable, and
per cent, may be added to the live load
of stringers as an additional precaution.
Experience, too often costly at that, can
alone decide the effect of $ie impact,
<fcc, caused by a live load. Its effect is
usually included by adding some per
cent, of the live load to the total load
regarded as static.
52. The weight of chords, in table
For the simple trusses just examined,
the determination of max. chord strains
is simple, but for compound trusses with
two or more systems of triangulation,
the method is tedious comparatively, and
in practice it would be best to ascertain
and tabulate for various spans and loads,
the percentages to add to the strains re-
sulting from the load regarded as uni-
formly distributed.
53. Permissible Strains per Square
Inch in Tension and Compressio?i.—lxi
Van Nostrand's Magazine for Nov. 1877,
p. 459, is an article by the writer on this
subject. A brief summary of it will be
given.
Weyrauch (see " Constructions of Iron
and Steel," Chap. XIII) deduces from
148
VAN NOSTKANTTS ENGINEEBING MAGAZINE.
Wohler's experiments, by Launhardt's
formula, the following value for the safe
strain in kilograms per square centimeter
=br to which wrought iron should be
subjected in tension.
y=2J!V*e)
where w= factor of safety, 6=
mm.
max. B
minimum strain that piece ever bears
maximum strain that piece ever bears
Impact, vibration, &c, such as a live
load causes is not included; and I as-
sumed that its effect varied inversely
with 6, and wrote empirically, for the
safe strain on wrought iron ties in lbs. per
square inch,
6=7500 (1 + 6) . . (7)
Also, the safe strain on wrought iron
columns in lbs. per square inch,
38500 l(i+0)
4 +
fo&W^J
(8)
where c=3QIq-q for pillars with jto ends,
c=-jy$Tnr for both ends hinged, and c=
2 4 otto" f 01* one end flat, the other hinged •
1= length of pillar in inches; d— diameter
in direction of bending in inches, and
r= radius of gyration of cross section
about neutral axis in inches. The factor,
38500
G)
— is supposed to be the crippling
1 + e
weight of the column. This term is
found not to be constant for different
forms of cross section as " square col-
umn,
" Phoenix,
" American
or
"common" column.* It would be pro-
per then to replace 38500 and the values
given above or found experimentally for
c, by the corresponding terms for the
particular cross section as found from
experiment.
54. The above formulae cause b to
diminish for web members more rapidly
towards the center of the span than
Weyrauch's formulae do. As impact is
more hurtful the smaller the member and
as the weight of web members diminishes
towards the center of the span this ap-
pears reasonable. Should we assume
* See Engineering Neivs (Chicago), January 31, 1878, for
proposed constants in Gordon's formula.
that b from impact alone varied with the
weight of the web member of a bridge,
the result would be somewhat different
from the above, since the weight of web
members increases pretty regularly from
the center to the abutments, whereas 6
increases most rapidly at first.
55. For the chords it will be suffi-
ciently near to put
q_ dead load of bridge
total dead and live load
Thus in the example art. 42 for chords
336000 _336_
~~ 336000 + 520000- 856
If the chord strains are determined by
supposing the bridge uniformly loaded,
then 6 is correctly determined as above.
56. Since the strain on any web mem-
ber is equal to the shearing force on that
member multiplied by sec. i,
^_(min. S) sec. t__min. S
(max. S) sec. i max. S'
for web members.
Then, arts. 26 and 27, and table art.
21 we get
Shearing
Forces
Panel
e
Max.
Min.
1
216108
77000
.36
2
181840
59112
.32
3
148960
39836
.27
4
117468
19172
.16
5
87364
— 5380
0
6
58648
—31320
0
As given in the table art. 42.
If the strains on the web members are
known, they may be used in place of the
corresponding shearing forces, if pre-
ferred.
57. We see that for a 200' span bridge
weighing 336000 lbs., that b, for tension,
is varied from 7500 lbs. per square inch
on counters and middle ties to 10420 lbs.
per square inch for lower chords. Ex-
tending the formulae now to other spans,
we should similarly find that for spans
of 0, 100, 200, 300, 400 feet, b would
vary from 7500 lbs. at center on web ties
to 7500, 9400, 10400, 11300, 12200 re-
spectively on end ties or lower chords.
When-^=10, nearly the same figures
a
MAXIMUM STRESSES 13" FRAMED BRIDGES.
149
apply to posts. Thus eqs. (7) and (8)
give nearly the same value for all values
of 6 when —=10.
d
58. When the engine comes directly
on a member, the effect of impact is
much greater than for the web members
and must be allowed for empirically;
thus we have added 50 per cent, to
stringers and floor beam loops, the latter
because of their small size.
For the floor beams we have supposed
M in B = o .'. 6 = o and 6=7500.
For wind strains values of b of 1500
for ties and 5000 for struts was used as
the conditions assumed are so rarely ful-
filled. It may be remarked that nothing
has been added to the chords for wind
strains, though its effect must be severe
on them, causing inequality of strain —
another reason why the chords should be
computed for maximum strains as in art.
40.
59. The above formulae (7) and (8)
may or may not bear the crucial test of
practice. It will probably be admitted
however that they possess great advan-
tages in properly comparing different
forms of trusses of the same span, to
which use they will be put in what fol-
lows. Empirical rules in ordinary use
are wanting in this; they do not* recog-
nize Wohler's law — that the minimum
strain sufficient for rupture decreases as
the difference between the extremes of
strain to which the piece is liable, in-
creases.
The deduction of Launhardt from
Wohler's experiments, that b varies with
6 is included in the formulas above; and
the coefficient of 6 was changed from £
as given by Weyrauch to 1 to allow
empirically for impact.
60. Gerber also deduced formulas from
Wohler's experiments including 50 per
cent, added to live load for impact.
Formula (7) above agrees very closely
with the values used in the Mainz bridge
by Gerber, though for #=§ to 1 his
formula gives much larger values than
eq. 7.
When 0=1, impact is supposed null
and 6=15000 lbs. This seems suffi-
ciently large, though Gerber gives in his
Mainz bridge and later formulae, 22760
lbs. per square inch.
01. The variable factor of safety for
posts,
1 I
4+foT
is used to give values for
a 200 feet span in accordance with the
recommendations and usage of American
engineers.
No formulae for wood is given, as no
experiments have been made after Woh-
ler's manner upon it.
62. The compression members in the
table art. 42 were supposed hollow
cylindrical and of wrought iron. There-
fore in eq. (8), r=-V2. The end upper
chord panels were regarded as " flat at
one end, hinged at the other;" the other
panel lengths as " flat at both ends."
The braces were regarded as " hinged at
both ends."
The panel length assumed may not be
the most economical. It is only by com-
puting the whole weight of the bridge
for different panel lengths that the pro-
per panel length can be determined.
The most economical height of truss will
be considered later.
63. The following table of " crippling
weights" may prove a convenience:
(See Table on following page.)
64. Maximum Chord Strains dice to
any number of equal or 'unequal weights
placed at -fixed distances apart.
Let iflj, ic\ .... at fixed distances apart
be placed on the girder AD, of span I.
Let R=w1 + ?o2 + m=2w} be the resultant
of 10^ io2 . . . in position and magnitude.
Fig. 8a.
ICi
&
T
■C >R
Call x the distance from A to wl9 C=
distance from u\ to R, a= distance from
A to the cross section whose max. mo-
ment, as the load moves forward, is re-
quired. We have Vl=~R(l—x—c).
1/. When w1 and w2 are on either side
of B, the moment at B is
M:
Ya-w1 (a-aj)= -JR (l-^)-^ [
a + lw1— R )x (9)
150
VAN NOSTRANLVS ENGINEERING MAGAZINE.
Hollow Cylindrical Columns.
1
d
Flat Ends.
One end
hinged.
Both ends
hinged.
^10 d
38500
38500
38500
^OOOtf2
^3000 d*
4- 73
^9000 d*
10
37663
37258
36862
5.
11
37492
37008
36535
5.1
12
37306
36736
36184
5.2
13
37106
36447
35810
5.3
14
36893
36139
35414
5.4
15
36667
35814
35000
5.5"
16
36428
35473
34567
5.6
17
36177
35117
34117
5.7
18
35914
34747
33653
5.8
19
35640
34365
33177
5.9
20
35357
33971
32688
6.
21
35064
33566
32190
6 1
22
34761
33152
31684
6.2
23
34450
32729
31171
6 3
24
34131
32298
30653
6.4
25
33805
31862
30130
6.5
26
33472
31420
29605
6.6
27
33133
30973
29079
6.7
28
32787
30523
28551
6.8
29
32438
30070
28025
6.9
30
32083
29615
27500
7.
31
31725
29159
26977
7.1
32
31363
28702
26458
7.2
33
30998
28246
25943
7.3
34
30631
27791
25433
7.4
35
30262
27337
24928
7.5
36
29891
26885
24428
7.6
37
29520
26436
23936
7.7
38
29147
25990
23450
7.8
39
28774
25547
22971
7.9
40
28402
25109
22500
8.
When lw1 — R j)>°i M increases with x;
i.e., M is a max. for x—a. (We must
not consider x X a, since V and hence M
would be diminished). If lw1— R-)>o,
M increases as x decreases, which moves
w2 up to B at last. When the coefficient
of x is zero, w1 or w2 may be supposed at
B, or 8 must lie between them.
2/. But M may be a max. when w2 is
to the left of B. In this case regard
w, + w8=Pasaa single force.
Call cx= distance from the center of
gravity of w1 and w9 to R, i.e., from P
toR,
and a;— distance from A to P.
Then the above equations hold, on
simply substituting P for wx.
As before, when (P— R-j>o, M in-
creases with x and is a max. when io2 is
over B, but it must not be supposed to
the right of it, as the equation does not
now include this supposition. This posi-
tion of the load then gives M a max.
3/. If, however, HP— R j)<o, M in-
creases as x decreases, whence the load is
moved forward so that ws rests upon B.
Next, calling w1 + wi + wz— PxJ c2=
distance from P2 the resultant of io1,wn,w3
in position and magnitude to R, and x=
distance from A to P; eq. (9) holds as
before on substituting Px for wx. We
proceed as before to ascertain if M is a
maximum when B is between wz and w4
and so on for other positions of the
loads. «
65. As w^ w2 . . . pass off the span,
they must no longer be included in the
formulae for R, c, M, etc. For a framed
truss, a is the distance from A to the
apex that is taken as the center of mo-
ments for the opposite chord panel. As
it is only necessary to consider half a
truss, the maximum strains in the chords
being the same for the other half when
the load moves in an opposite direction,
we must not take a>i I.
66. Example. Consider the three
trusses, Figs. 5, 6 and 7, to be of 400
feet span, each with 20 panels, the panel
lengths thus being 20 feet each. Let
five equal weights w (as the locomotive
excesses, art. 16, 38) be placed on the
span at equal or unequal distances apart.
Then R— 5w and in eq. (9), lw1—'R-)
=icll — — ), which is positive when a<
80 feet; hence art. 64, 1, to find the
maximum chord strain on the first four
panels from the abutment, the loads
w, id . . . must extend from the cen-
ter of moments for the panel considered
(art. 65) towards the center. For the
fifth chord paneHl j\ is negative, so
that the second weight moves up, at
least, as far as its center of moments;
then proceeding as in art. 64, 2; P=2w,
and (F— Uj\=w( 2— %r- J is +, so long as
«<|i=l60 feet. So that for panels
5, 6, 7, 8 (and 4 if preferred), the second
MAXIMUM STRESSES IN FRAMED BRIDGES,
151
weight must be supposed up to the panel
considered, to ascertain its maximum
chord strain.
Finally, \2 — -j\<o for «>160, or 8
panel lengths. Therefore in art. 64, 3,
put F=3w .-. /Pi-R'-)^3-^)is +
31
when «<— :
5
240 feet.
Hence for panels 9, 10, (and 8 if de-
sired) the middle weight is placed at
their center of moments.
The above results are independent of
the distances apart or magnitude of the
equal weights. It is seen that the maxi-
mum moment for an end panel is when
the front weight reaches to it; whilst
the max. moment at the center is when
the middle weight is at the center, and
for intermediate panels the loads have
intermediate positions. It will be in-
structive for the reader to test the above
results, by assuming various positions of
the loads for each panel in turn.
When the loads are unequal the appli-
cation is equally simple and direct.
67. Referring to eq. (9), and regard-
ing w1 as the resultant of all the weights
to the left of B, we see (as was remarked
in art. 64) that when a has such a value
that,
R
wj,— (wx + w^ + . . . ) a=o
to.
w2 + w3 +
I- a'
that the greatest moment ever experi-
enced at B obtains; and we see from the
last eq. that this occurs when the loads
on either side of B are in the ratio of the
segments into which it divides the span.
This conclusion is reached in DuBois,
Graphical Statics, art. 73. Though this
author seems to regard the analytical
treatment of a given recurring system of
moving loads as almost impracticable,
(see his Preface, p. xi.)
It is believed that the above solution
is practical and simple; in fact, much
more so than the one by the graphical
analysis.
COMPOUND SYSTEM.
68. As the span increases, the panel
lengths become too long for economy,
or the inclination of the web diagonals,
for usual panel lengths, is not the best
for economy, for the trusses previously
figured. Hence the use of compound
systems such as the Whipple, fig. 9, the
Trellis, the Post, or even bridges of
"treble" <fcc. "intersections," where the
ties cross three or more panels.
69. Web Strains. — In the truss fig. 9
of 200 feet span and 28 ft. high, divided
into 12 panels, weights as before, let w,
placed below the apices, denote the
panel dead load ; p placed above the
apices, the panel car load ; and E, the
locomotive excess, being the two weights
at d and h in the figures. It will be no-
ticed that any weight as that at f can
travel to either abutment only by one
web system, as a B d D fH h J . . . .
The weight at e must follow the other
system, a B c C e . . . . The weights
inked black thus travel towards either
abutment only by the first system, the
others by the second.
Now if the second engine is placed 50
back of the first, its position is g j but
the interposition of a car 16f feet long,
or different engine and tender lengths
would locate it at h. As the object is to
find the max. strain that can come upon
each system in turn, we must place the
second locomotive four panel lengths
from the first, so that it will bear upon
the same system as the first. This posi-
tion may rarely happen, but it should be
provided for in the sections of the web
members, especially those near the cen-
ter of the truss, such as the dotted
"counters." The dotted lines Bb and
12 are " suspenders " like those in Fig. 7
and similarly strained to a max. of 46000
pounds.
70. The weight at I may be taken on
either or both of the partial trusses into
which we shall suppose Fig. 9 divided.
As it only affects V, ^ (io+p) = 2555
pounds in this instance, it may act with
a different system from that taken, with-
out altering the sections an appreciable
amount.
With vertical end posts there is no
uncertainty, for then the weight at I can
only act with the black system, as a tie
extends from I to top of end post, the
tie from Jc being also carried there.
71. If we cut the truss through be-
tween cC and clD as in Art. 7, and apply
forces at the cut parts equal and opposed
IS 2
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Fig. 9.
iciiliiil
k I «i
to the resistances, the total shearing
force, S, is, of course, Y—2w; but S is
the sum of the vertical components on
the two cut ties, and without knowing
the amount carried by one tie we are
unable to estimate it on the other. Hence
this general method must first be applied
to one partial truss and then the other
independently. First take the partial
truss aBdD/Fh . . . . , and call Y the
reaction at a due to the load on this
truss. The reasoning of arts. 12 and 27
apply here in finding max. and min. S.
Call 2w the sum of the ws between a
and foremost locomotive on system
taken; then having found Y, when load,
(engines in front) extends from farthest
abutment we have
S=Y— 2w. Take moments about m,
14000, ^JULoo.0
Call llt the lever arm of E,
£2, the lever arm of the resultant of
the car loads p,
and m=ihe number of jo's on the partial
truss considered. Also let a panel length
as ab be the unit of length. With the
loads as in the figure ^=7, lq = 5, m=5.
We, have as before, w
and E = 60000.
Vl2 = Qw6+El1 + mpl<2
.'. S = 42000 + 5000.Z1 + W2.1390.Ja — 2w.
In a similar manner we proceed for the
other partial truss, finding the equation,
2 12 x 12 2
72. The results are entered in the fol-
lowing table. Note, from the figure,
that as the live load moves two panels to
the right, lx diminishes by 2, £2 by 1, and
m by 1. The table is thus very quickly
formed. The max. shearing force on
aB + 216108 lbs., found by supposing the
whole bridge loaded as in art. 21. Thus
F
Y = S=mw+p) + 9iX — = 216108.
Partial Truss aBdDfF
Front Engine at
Piece.
42000+5000. Zi+wi.l39(U8 -Jw>-
IS.
d
f
h
J
I
m
dD, D/,
/F, hF,
42000+5000 . 7+5 . 1390 . 5 - 0
42000+5000 . 5+4 . 1390 . 4-14000
42000+5000 . 3+3 . 1390 . 3 - 28000
42000+2500.3+2.1390.2-42000
42000+2500. + 1390 -56000
97750
61240
27510
- 940
-24110
Partial Truss aBcCeE ....
35000+5000 . Zi+m. 1890Z3 -Ew
c
e
9
i
k
Cc, Ce
eRtgR
gGr, iGc
35000+5000 . 8+5 . 1390 .6-0
35000+5000.6+4.1390.5-14000
35000+5000 . 4+3 . 1390 .4-28000
35000+5000 . 2+2 . 1390 . 3-42000
35000+2500 .2+ 1890.2- 56000
116700
78800
43680
11340
-13220
73. Be careful to note when one loco-
motive leaves the bridge and modify the
formula correspondingly. S sec. % gives
the strain on the ties as before, sec. i=
43 5
— '- —1.553 except for Be/ its value for
32 6
that tie being —^- = 1.165. The values
28
of S above are the actual strains on the
vertical posts opposite them. If those
posts were inclined as in the " trellis "
bridge (in which the posts ~Dd, F/, &c.i
take the positions, Ec?, G/j &c. ; the cor-
responding ties /T), AF, &c, the posi.
tions/E, AG, <fcc; braces reaching from
MAXIMUM STRESSES IN FRAMED BRIDGES.
153
C to b and from K to I), we multiply S
by sec. i to find the strains on them as
well as the ties that are equally inclined.
In the trellis, as in the triangular, some
web members near the center take ob-
verse and reverse strains.
74. It is implied in the previous com-
putations that the reactions at the abut-
ments of each partial truss are to be de-
termined by the simple law of the lever
independently of the other partial truss.
Unless the counter rods have little or no
strain on them for a uniform load this
assumption may be incorrect.
To prove it: take the extreme case,
that the main ties Be, Ce, Kg, are too
long to be in action, and that counters,
from c to E, eG, g\ are taut (malicious or
ignorant persons might screw up the
counters so as to relieve the main ties
above from strain), then the loads c, e
and g must inevitably go to m. Xow
conceive panel cD severed. The total
shear on this panel (art. 71) is,
Tr n Uw 7E 9/>
2 T 12 r 12
2w = 146500
=s.
But since the shear w on the supj:>osed
rod c E acts up, the actual shear on tie
b D is S + w= 160500 lbs.; whereas ice
shall proportion it for 97750 lbs. shear as
previously found? Similarly for other
panels. Practically, the counters are
loose when the truss is first set up; the
main ties are then necessarily in action;
for even if a little long (^ inch say), the
roadway sinks the apex and thus brings
them into action (as the upper chord
apex sinks too, the chord at this apex is
thus unequally strained). Xow, if the
counters are tightened, part of the
weight at c, e, . . . will go to m, from
the law of decomposition of forces; and
the greater the initial strain on the coun-
ters, the larger the weight on the partial
truss, «BcCeE . . . that is transferred to
the right abutment. The counters being
of much lighter section than the main
ties will stretch more and thus counteract
this tendency, especially on the partial
truss on which the locomotives bear.
95. As stated then, the partial trusses
cannot act independently except when
the counters are not strained for a uni-
form load. If they have a slight initial
strain on them, the strains may be in-
creased on the web members somewhat—
an additional reason for supposing the
second locomotive to bear upon the same
system as the first, as we have done. It
is then not only useless, but may be
prejudicial to put counter rods, screwed
taut, in panels where there is never any
j reversion of strain, as from c to E etc.
j With the loads assumed, S is — , (art. 73)
{ for counters d F and j H, but a slightly
greater load would bring them into ac-
; tion, hence they should be retained and
their section assumed, say at 2 sq. in.
76. The preceding reasoning applies to
I all compound systems. In finding S for
the simple systems, as figs. 5, 6, 7, no
I assumption was made as to the abutment
! to which any particular weight was
\ transferred. But S is the total shear,
; and for figs. 5 and 6, if the counter car-
I ries any strain (as explained in art. 74)
the shear on the main tie or brace is in-
creased by that strain.
In the triangular truss, fig. 7, there is
no uncertainty as to the strains; as the
same piece, where necessary, takes ten-
! sion and compression both.
77. It is recommended as good prac-
tice, where separate counter rods are
used, " to put a light load on the bridge
and then strap the counters down taut.
They should not remain taut under full
symmetrical loads, but should be tight
enough to keep quiet under unsymmetri-
i cal loads; a medium that can be struck."
j " Practically the counter ties remain
| tight if adjusted intelligently and are not
j tampered with." Similar remarks apply
to " keeping wooden counterbraces "
I recommended by Haupt. As any deflec-
tion of a truss is accompanied by an in-
! creased length of main ties, and a short-
ening of the counter diagonals, if the
counters are strapped down when there
j is a light load on the bridge, for a full
i symmetrical load they will be loose; for
a dead load only, they will be tight.
This is as it should be.
(Remark. The whole of the rear-
most loc. excess was supposed to bear
at one apex only, thus giving slightly
larger strains than the true ones, to alloio
somewhat for improperly adjusted coun-
ters.)
78. Chord Strains. — Suppose the truss
loaded at each lower apex with {to -hp)
=w' (the weights below the fig. can now
be taken for w') and of the two weights
154
VAN NOSTRAND7S ENGINEERING MAGAZINE.
30,000 lbs. each, either 3 panels (50 ft.)
apart, or a greater distance, if the chord
strains are thereby increased.
As before, we assume that each partial
truss acts independently of the other;
find the strains on any chord piece as
CD, due to each partial truss and add
them for the total strain on that mem-
ber. If it is simpler, the reader may
draw the two partial trusses separately
to estimate the effect of each.
79. The Locomotive Excess, E=60,000
lbs., is made up of the two weights,
30,000 lbs. each. For convenience call
the foremost P, the rearmost, P'.
Now the chords may receive their
maximum strains when P and P' act in
the same system, 4 panels apart; or in
different systems, 3 panels apart. The
principles of art. 34 are of some assist-
ance, but we can only determine by
actual trial, for each chord panel in turn,
the proper relative position of P and P'
that give the max. strains for that panel.
Hence I have estimated the effect of P
and P' separately, and have taken those
positions of P and P', either 3 or 4 pan-
els apart, that gave the greatest strains
for each chord panel. The height of
truss was taken as before at 28 ft. The
results are as follow:
Piece.
Pat
P' at
Max.
Strains.
P, 4 panels
from P'.
lbs.
lbs.
ac
b
e
28274
—
cd
c
g
47619
47619
de or BC
d
h
62500
62500
ef or CD
d
g
75893
71433
fg or DE
e
h
84821
74410
EF
f
I
87798
71433
FG
f
I
87798
71433
Thus for cd, de and BC, the weights
are 4 panels apart, for the others 3.
Note again, that for some panels P is ad-
jacent, and for others a panel distance
from, the panel considered. It will be
noticed above that for panels near the
centre the strains are considerably great-
er when P and P' are 3 panels apart,
than when they are 4 panels apart.
80. To illustrate the method of com-
putation, call a panel length=ab—l ;
the height of the truss is then 28-f-^-=
With P at c, its reaction at a is \%
84
50'
P.
If de is cut, rotation about, C would
occur. The moment about C is ^f P. 2
= 50000. Next suppose P at d, the re-
action is f P. If de is cut, D is the point
of rotation, and the moment is thus f P
3 = 67500.
Now when P is at c, conceive P' at//
its reaction is TyP; and with D as a cen-
ter of moments for de cut the moment =
-fa P 3 = 52500. (It is needless to consid-
er P' at g, in this case, as V is less, also
the point of rotation, for de cut, being
C, for the truss g E e V . . ., the lever
arm is less too).
Next with P at d, let P' be at g .*. V=
i P. Then for de cut, the moment about
C is i P. 2 = 30000.
Lastly with P at d, conceive P' at h .*.
V=T52 P. For ~de cut, D is the point of
rotation for truss h F/D . . . ., hence
the moment is fa P. 3 = 37500.
Collect now the moments for the piece
de.
Piece.
Pat
Moment
P' at
Moment
Total.
de
de
de
c
d
d
50000
67500
67500
/
9
h .
52500
30000
37500
102500
97500
105000
With P at d and P' at A, the actual
moment is greatest. Divide it (105000)
by the height of truss -££ and we get the
strain in de= 62500 lbs.
81. We see how much simpler the
treatment of the simple systems is than
the compound; still, if we desire to know
the " true inwardness " of the compound
systems, extra work is unavoidable.
It may be urged that when P' passes
to the right of all the counters none of
its weight can be transferred to a : true,
but with the uniform load in addition on
the bridge, the law of the lever holds
for each partial truss, since counters are
designed in those panels where loads
have to be transferred to the farthest
abutment and the effect must be the same
in the final summation whether the two
engines and the uniform load are treated
separately or conjointly.
82. For the uniform load, w'= w+p=
14000 + 16666 = 30666 per panel; as- be-
fore we assume that the partial trusses
act independently and afterwards com-
bine their effects for the same chord
panel.
MAXIMUM STRESSES IN FRAMED BRIDGES.
155
Thus to find the strain on BC due to
the black weights: V=%Q w\ with d as
a center of moments,
(Strain on BC) X dD =Y xa~d-iof X~o~d
Similarly for the other partial truss,
conceive be, Be and BC cut and take the
intersection of the first two, c, as a cen-
ter of moments (art. 36). The reaction
at a is V=|V
.". (Str. onBC)xCc=V'xoc
The sum of the strains on BC thus
found, added to that found for the loco-
motive excess, gives the total strain on
BC which is evidently the same as that
on de.
83. The following is a more conven-
ient method. The reaction at a due to
the black weights is 3io'; hence (art. 7),
the shears on &A, dB, fD are 3io\ 2wf>
w', respectively as is marked, on the half
truss with vertical end-posts, Fig. ]0.
The shearing forces on the ties of the
other partial truss are as marked on
Fig. 10.
-~- id tan:i
A tyiio B 2w C \y2w D
E H*C
pi:
■2}2u\
*& X-
K
b c\ d\ t\ ju y
& $± 1 1 r a
in.' »«' )/i w in in
them 2j?//, ljw', %w'. In fact | of the
w' at g (Fig. 9) goes to either abutment
(if the counters do not act). At E the
pull on the tie # E is decomposed into
\w' acting down the post Ee and
\w' tan. i, compressing EF, (i=g Ee).
At e, the \w' + wr(ate) acting verti-
cally, is _decomposed in the directions
Ce and ef thus giving the strain on
ef= 1 \w tan. i. The shearing force on Ce
is thus ljw'. Hence the pull on Ce at C
gives 1-^w/tan. i7 strain on CD, and ljw'
strain on post Cc; and so on for all the
weights, except that the pull on A£,
causes a strain on AB of 3 w' tan. aAb
=fw'tan. i. Put aAb=i1. The total
strain on AB=(f + 2£)w' tan. i— 3w'tan.
i1 + 2^w' tan. i.
Strain on BC=strain on AB + 2w' tan. i.
Strain on CD = strain on BC + 1-kw' tan. *.
<fcc, &,Q.
Similarly,
strain in bc=3w' tan. i^^w' tan. i.
strain in cd— strain in bc + 2^iofta,n.i, &c.
Hence the rule.
Multiply the shear on each inclined
web piece by the tangent of its inclination
to the verticcd. The summation of these
products from the abutment to any chord
piece gives its toted strains.
If the chord strain at center agrees
with that found by moments the whole
work is correct. This method can be
applied to any truss.
83. Now by the principle of moments,
the expressions for the strains in BC,
CD . . . , cd . . . are the same for Figs.
9 and 10. In fact the same method may
be applied to Fig. 9, regarding the in-
clination, &c, at the ends, and the above
rule deduced. The strains for the truss
Fig. 9 are entered in the following table.
By computation, we find, tan. £=1.19;
tan. ^ = .595.
84. The total strain on ac Fig. 9 is the
same as for Fig. 7, 128669 lbs. Since
the shear on «B is *£- w' we find the
strain on ac due to uniform load ^-w'
tan. ^ = 100354.
From table, art. 79, the max. strain
due to E is 28274 which gives 128628
lbs. strain on ac. The difference, 41 lbs.,
between this result and the former is
due to carrying tan. i to two decimal
places only.
Piece.
Increments.
Strains.
be
5iw' tan. i1
100354
100354
cd
2\io' tan. ix
45616
145970
de or BC
2 w' tan. i
72984
218954
ef or CD
liio' tan. i
54738
273692
fg or DE
to' tan. i
36492
310184
EF or FG
\w' lan. i
18246
328430
156
VAN NOSTRAND7 S ENGINEERING MAGAZINE.
Taking moments about g we have
Strain in FG=(4f w.l00-5w.50)-^28
= 328550 lbs.
The slight difference between this re-
sult and that given in the table, shows
the correctness of the work. The "in-
crement " column can be " run up " from
the bottom, adding — tan. i each time
until we reach cd.
85. Combining these results with those
in art. 79 we enter them, also the web
strains in the following table:
Piece.
d.
I
Ti
til
//
Strain.
e.
b.
Area.
Length.
No.
k.
Weight.
Totals.
//
D"
'
lbs.
U. Chord, BO
13*
15
3
4
281454
.39
9050
31.1
100
— 6~
4
10
IT
6911
CD
11
1
349585
a
9270
37.7
1 1
< i
1 1
8378
DE
"
"
il
395005
"
a
42.6
"
ci
«
9467
EF
it
a
416228
a
<<
44.9
<(
"
((
' 9978
FG
30
416228
251766
ti
.36
It
5340
44.9
47.15
t i
32.6
n
<<
((
it
9978
44712
Posts, aB
20495
Cc
10
34
i
78800
.17
4400
17.9
28
«(
<«
6683
J)d
u
i
61240
0
3750
16.3
"
"
a
6085
Ee
n
<<
A
43680
0
"
11.62
"
<<
it
4338
F/
8#
40
1
27510
0
3140
8.76
it
ti
u
3270
Off
a
11340
1476889
46000
0
.39
0
10420
7500
8.76
141.73
6.13
100
28
2
4
1 1
tt
n
1635
42506
Lower Chord
31496
31496
Suspender Bb
2288
Ties, Be
135955
.3
9750
13.94
32.6
< <
a
6064
Bd
151806
.25
9370
16.2
43.5
< <
n
9396
Ce
122376
.17
8780
14
1 1
ti
it
8120
w
95106
0
7500
12.7
"
it
ft
7366
Bg
67835
0
7500
9.04
"
1 1
< t
5243
¥h
42723
0
7500
5.7
1 1
-'
"
3306
Qi
17611
0
7500
2.35
i c
1 1
t<
1363
Hj
2.
a
it
<(
1160
44306
86. The value of 6 for the chords is
the same as in the previous truss ex-
amined, also for a& and bB. From the
table of shearing forces (art. 7 2), we
find the following values for 6, accord-
ing to the principles of arts. 26, 27:
Piece.
Maximum S.
Minimum S.
6.
aB
216108
77000
.36
cB
116700
35000
.3
dB
97750
24110
.25
Cc, Ce
78800
13220
.17
Dd,D/
61240
940
0
Ee, Eg
73680
11340
0
The black weights were regarded as
acting on the same partial truss. Min.
S on cB is then due to dead load only,
and is 35000 lbs. = 2jw. Min. S on dB
is the same as for L/ when front engine
is at I (art. 72). Similarly min. S on
Cc, Ce is the same as for &K, Ki when
"front engine is at k" The dotted
counters and hence the posts F/ Gg
sustain no strain from a uniform load.
Hence for them 6=o. It will be noticed
that for the same panel 6, and hence b
is less for the " compound " than for the
" simple " systems. In the foregoing
table the posts were regarded, as " hinged
at one end."
87. The following is the
Bill of Materials.
Whipple Truss— 200' span— 28' high.
lbs.
Posts 42506
Upper chord 44712
20 p. c. for castings, &c 17444
Ties, counters and suspenders. . . 44306
Lower chord 31496
15 p. c. on two last, for bolts, &c. 11370
Floor beam loops 5000
Lateral bracing 11400
Floor beams (iron) 24500
Iron stringers 60000
Rails, cross ties, &c ■ 33200
Total weight of bridge 325934
Assumed weight 336000
Assumed weight too great by 10066
MAXIMUM STRESSES IN FRAMED BRIDGES.
157
The weight of this Whipple truss
(325934) is thus 3915 lbs. less than the
weight of the Triangular Truss (329849)
allowing y as the least thickness of
metal. If, however, as seems more
proper, the vertical posts of the triangu-
lar truss that only sustain 2500 lbs. dead
load, be given a thickness of ^ inch,
their section will be 4.5 square inch; and
the weight of the triangular truss is re-
duced 4200 lbs. making it the lightest of
the two. The weight of flooring, rails,
loops, lateral bracing, etc., was assumed j
the same in both trusses. See art. |
108 for a further comparison.
88. The Quadrangular Truss however,
is more built than any other in this
country, on account of its economy in
first cost, the square joints being more
easily and accurately machined than
others; the posts too are vertical, thus
ensuring less flexure under their own
weight than inclined posts, and with cer-
tain details they can be made " flat at
both ends," bearing against the upper
chord and the upper flange of the floor
beam.
It is evident from what precedes that
" compound systems " require greater
accuracy in filling than simple systems;
and where counter rods are used, they
should be properly tightened and often
inspected, or grave consequences may
ensue. It is evident, likewise*, that the
greater the number of systems used, the
more care is required to make the actual
strains agree with the computed; in
other words, to cause each partial system
to act independently of every other.
The investigation of the maximum chord
strains is more troublesome the greater
the number of partial systems used.
Many of the largest spans built or being
built in this country, varying from 300
to 525 feet in length, are " double inter-
section," although treble and quadruple
intersections are by no means unknown.
In latticed bridges where the diago-
nals are connected at their intersections,
the strains are perfectly indeterminate,
It would certainly then seem advisable
to use those patterns of web in which
the strains go where they are computed
to go.
The weights computed above are, so
far as I know, above average. Are they
too great for a first-class road ? The
effects of high speed, with snow, great
cold and side wind (for which no pro-
vision is made in the chords), ill fittings
and perhaps some counters unadjusted
should be considered conjointly with the
statical loads in answering this question.
89. Let us now suppose the live load
uniformer'y distributed, and ascertain
what percentages are necessary to add
to the chord strains induced to equal
the maximum chord strains (see art. 52).
The uniform live and dead load per
panel is now (168000 + 200000 + 60000)
-7-12 = 35666 lbs. which causes the fol-
lowing strains in the chords (see art. 84
for method of ascertaining strains):
BC = 254654,
CD=318317,
DE = 360759,
EF=381980
FG=381980
whence comparing with the maximum
strains given in the table, we find that
for BC and CD, we must add 10 p. c,
for DE, ty and for EF and FG, 9 p. c.
to strains just found to get the corre-
sponding maximum strains. The per-
centages are greater, except for end
panels, than for the simple systems (see
art. 52); hence a comparison of weights
based on the same percentage, is favora-
ble to the compound system, as drawn
in Fig. 9, at least.
90. It is worthy of note that the strains
in the chords are greatest where the shear-
ing force is zero.
This is evident from the reasoning in
art. 83 : for as the increment of strain is,
the shear 07i the tie X tan i; where the
shear on the tie is zero, the chord strain
is a maximum. Thus, in Fig. 10, since
5=o on tie FA, there is no increment of
strain to add to the strain on EF, at F.
At E, -J- w tan i is added to the strain on
DE etc. We see then, that EG is more
strained than any other part of the up-
per chord.
Similarly for irregular loading.
The above result is true, irrespective
of the number of panels, hence for an
indefinitely great number, as we may
suppose a solid beam made up of.
This result must not be confounded
with that of art. 64, where the object
was to find that position of the load for
which a particular chord piece would be
strained most.
91. Let us now estimate the Whipple
as a deck bridge with leaning end ties,
158
YAK" NO STRAND'S ENGINEERING MAGAZINE.
trusses 14' apart from centre to centre.
Thus in Fig. 9 extend the upper chord
to the abutments at A and M, discard
Be aB and ab; draw the ties 5 A, cA and
the post Bb (similarly at the other abut-
ment) and conceive the load on the up-
per chord. The chord strains are the
same as for the through bridge, Fig. 10;
the maximum shear on the ties is the
same as before, but the maximum strain
on a post now is when the front engine
is directly over that post, or two panels
nearer the abutment than before, thus
increasing the strains on the post over
those formerly obtained. On this ac-
count 0 is not the same for the posts as
before. The results are entered in the
following abridged table of weights,
from which the Bill of Materials is made
out as before. To avoid mistake in de-
termining " min. B" the partial trusses
may be drawn separately, when the
principles of art. 27 apply directly:
Piece.
d
I
d
th
Strain.
e.
b.
Area.
Length.
No.
k.
Weight.
Totals.
"
"
lbs.
U. Chord, AB
m
15
193589
.39
9050
20.1
100
~~5~
4
AIL
4467
BG
12
28
1
1858500
137000
< t
.3
9270
5840
200.5
23 5
1 1
28
a
<<
44556
49023
* Posts, Bb
8773
Cc
"
"
T9*
116700
.3
5840
20.
"
"
7466
T>d
"
u
*
97750
.25
5610
17.4
"
<(
6496
Ee
10
34
#
78800
.17
4400
17.9
( c
< <
6683
F/
<(
"
±
61240
0
3750
16.3
'<
"
6085
Gg
46000
1346987
159605
0
.39
.3
3750
10420
9750
12.3
129.2
16.4
100
32.6
2
4
1 1
2296
37799
Lower Chord
28711
28711
Ties, Ab
7128
Ac
181235
.3
9750
18.6
43.5
"
"
10788
Other ties (as
before)
43 5
<<
35954
53870
Bill of Materials.
Whipple Truss (Deck)— 200' span— 28' deep.
lbs.
Upper chord and posts 86822
20 p. c. for castings, &c 17364
Ties and lower chord 82581
15 p. c. for bolts, &c 12387
Lateral tie rods and struts 11400
13 floor beams, 24" deep 22630
Iron stringers, 26" deep 60000
Rails, cross ties, &c 33200
Total weight 326384
Assumed weight 336000
9616
MINIMUM MATERIAL.
92. The most economical inclination
of the web ties, irrespective of the rest
of the bridge, is easily found to be 45°.
Thus call x the height of truss, d the
horizontal distance between the extremi-
ties of the tie, i its inclination to the
vertical, and s the shearing force on it.
The strain on the tie is thus s sec. i; the
cross section s sec. i-^-b, and as its
length is *J d* + x* its volume, is since sec.
v=
S cF + x*
which is a minimum for x=d, or when
^=45°: i. e., the material in the web ties
is a minimum when they are inclined ^45°
to the vertical.
93. The same would be true for the
web struts, if b was assumed constant
for them, but b = the strain per square
inch allowed, diminishes with the length
of the strut, and the above simple rela-
tion does not hold. The general law of
maxima and minima is this: that any
function of a single variable is a maxi-
mum or a minimum for those values of
the variable derived by placing the first
differential coefficient of the function
equal to zero. Thus, v= a maximum or
a minimum in the eq. above when
dv 2x2-di-x'i
— — =o .'. x=a
dx x
I It is evident that x=d gives a min.
MAXIMUM STRESSES IN FRAMED BRIDGES.
159
. , d3v 2d* .
It is proved by noting that -=-% = — 3 is
CltlC <)C>
positive; for as the second differential is
[±1 the function is \ a mm- i for that
L J (a max. \
value of the variable.
94. Having given for a trass with
parallel chords, the span, loads, panel
lengths, pattern, details, and formidce for
" b " — the unit strains required the most
economical height of truss ? Denote
the weight of the material that varies
with the height of the truss (since it is a
function of A), by F (A). This material
is such as given in preceding tables, as
computed from the strains on web and
•chords. The castings, both etc., trans-
verse bracing, flooring system, pins and
loops, do not vary perceptibly with A,
hence F (A) = weight of material com-
puted on chord and web strains only;
which is easily selected from the table of
weights. Now, if F (A) is a minimum
we must have
d¥h
dh '
lim
F(A + A A) -FA
A A
(10)
95. Denote the weight of upper and
ower chords, that varies with A, by
Fig. 11.
Wc ; also denote the variable part of
the weight of a web member by to, its
inclination to the vertical by i and its
length by /.
Now change the height of the truss
(see Fig. 11) to A + A A and call the new
value of I, I -\- A I.
96. As by assumption, the panel
lengths remain the same as well as the
diameter of the upper chord, the strains
in, and hence the weight of, the chords
are now ^ of the first, A and A + A A
h + A
being respectively the former and
present lever arms of the chord strains.
.'. New weight of variable material in
chords,
W'c =WC 7— h— = Wc - Wc
A + a A
AA
A + a A
(11)
97. If S denote the shear on the web
member, whose weight (the part that
varies with A) was w, inclination to
vertical i and length I, the former strain
on it was sec. i=S 7- and hence its vol-
h
S A\ ^
ume was __l«=7-r.
b bh
The new volume is similarly,
s(i+Aiy
b'(h+ A A)
in which, for struts (see art. 53)
38500(1 + 0)
and ^^equals the same expression on
changing I to (1+ Al). For ties b = bf=
7500(1 + 0).
Hence the new weight of the variable
material in the loeb member =ioX ratio
of new to old volumes
h b
(12)
_ (i+ Aiy _
w r 'h+Ah'b'
Actually dividing b by b'; for struts, we
get
*-+
«4)('+^)
= l+kAl,
For ties this ratio is 1. Hence to
avoid complication, simply notice that
for ties the fractional term k, in the
value of ,, for struts is zero, and as a
consequence, when a tie is considered,
the term m given below is zero. Now
substitute the above value of j-, in (12)
and reduce.
The first term of the 2nd member
must now be written,
{i+Aiy a
w
r h+A/i
:W-hlV
2hlAl + hAl'i-l2Ah
Fh + l2Ah
So that the new weight of the web mem-
ber is
160
VAN NOSTRAND'S ENGINEERING MAGAZINE.
w + w-
2hlAl + hAl3 — I2 Ah
Th + FAh
(1+ AlY hkAl
+ w-
\=w'
r h+Ah
and the sum of these, for the whole web
we indicate by 2io' = 2w + 2, &c.
98. Now, F(A)=WC + 2w
F(A+aA) = W'c +2io!
F(h+Ah)-F(h)_ Wc
A A
h+Ah
2w'-
Ah
Now by the principles of limits; Urn.
— -=cos. i. as A A and therefore A^di-
Ah •
minish indefinitely.
Hence for a minimum weight
bridge,
dFh_—Wc ^/2h cos. i—l
dh ~ h \ lh
of
+ cos. ixlim. k)
— O
The Urn. k we find by making Al=o
in the value of k. Now since cos. i=
— , the above becomes on multiplying
through by h
Wc= 2\^-l+l(Um.k)l\
to
2h*
Now, -75- — 1 = 2 cos.V— l=cos. 2 1
And
(Urn. k)l=
II l2\ , /. , - l\ 2c^a
(»4) (■«>)
Or putting (lim.k) l=m, and reducing:
m= i
+ 2
l40+5
1 + c-
1
. . . (13)
whence we find the following simple re-
lation:
Wo = 2i
(cos.2 i + -—m) .... (14)
.*. When the truss has the most economical
height, the variable weight of the tivo
chords must equal the sum of all the terms
found by multiplying the variable weight
of each iveb member by the cosine oftiuice
its inclination to the vertical plus a term
varying ivith the ratios of h to I and of I
to d; noting that for ties, or 2^osts where
b is taken constant, this last term (-^ m J
becomes zero.
For vertical members, i=o, cos. 2 i=l
and h=l.
99. For i<45°, cos. 2 i is +; fc450,
cos. 2 i=o; i>45°, cos. 2 i is — .
The above result is true for any pat-
tern of truss whatever with parallel
chords in which the strain on the chords
varies inversely as the heights and the
shear on any web member is not altered
by a change of height.
The result then, it seems, applies to all
usual forms of trusses with parallel
chords.
100. Let us draw a few general con-
clusions from our formula :
1/. The depth of deck bridges with
vertical end posts should be less than
that of through bridges of same design,
since the posts are heavier and thus W c
must be greater to satisfy eq. 14, which
requires a lower truss. With no end
posts for the deck bridge, if the web is
thereby lighter the reverse may be the
case.
2/. The greater the number ^of panels,
the heavier the web, for the same height,
which requires a lower truss to bring
about, the equality of eq. 14 (supposing
Wc for the same height to be the same
for any number of panels, which depend
upon the relative unit strains of upper
and lower chords).
3/. Continuous girders should have a
less depth than simple girders, since for
same weight of web, it is known that
Mc is less than for a simple girder.
4/. Trusses with two or more web sys-
tems should be built deeper than similar
designs with one web system, since cos.
2 i is nearer 0 in the first case, hence
Wc should be less and the truss higher.
101. If we suppose b (^strain per
square inch) constant for braces as well
as ties m=o and eq. 14 becomes
Wc =2w cos. 2 i
(15)
In Van Nostrand's Magazine for Jan.
1877, p. 42, is an article by Emil Adler,
C.E., on the most economical depth of
girders, in which he deduces the equiva-
lent of eq. 15. The general method fol-
MAXIMUM STRESSES IN" FRAMED BRIDGES.
161
lowed above is founded upon that of
Mr. Adler; but it will be found that the
supposition that b is constant will not
give correct results in practice, hence I
gave b the variable value, art. 97, and
find the results to agree closely with
practice. This should be so, since the
value of b assumed agrees closely with
values now used in America.
102. If all the web members are in-
clined 45°, as in the Warren girder cos.
2 i=o .'. Wc = o or the height of the
truss is co . Hence 45° is not the most
economical angle — on the supposition
that b is constant — for this truss. It is
hardly probable that eq. 14 would change
this conclusion, which is different from
that often given in text books.
103. Applications. — In the Triangular
Through Truss, Fig. 7, it was assumed
that the unit strains are constant for all
members but the three braces in the
half truss, hence m=o except for braces
1, 3, 5.
From the table art. 42 we find
Weights of chords =WC = 74,947
" vertical members = WV = 14,336
" ties and counters=Wt = 29,580
" 3 braces=Wb = 46,879
Now, z=30°46' .*. cos.2z=.477; and for
3 braces, -7=30'y also in eq. 13 for
the new weights of chords and web from
eqs. (11) and (12). -^g
Thus in eq. (11) making AA= — 1, we
find the new weight of the chords to be,
W'c = 7494"/ ff=77723.
Similarly, the new weight of vertical
members is,
W'y = 14336 ||=13824.
From eq. (12) making -77= 15 we get the
new weight of ties and counters,
W't = 29580 (|l^y.f$=29000.
And from the same eq. (12) we find the
new weight of braces 1, 3 and 5 to be
w'b = 46880(S)!#T'= 44455-
The braces were assumed, as before, of
13_i_" diameter. The new length of a
brace is 31 '.7; hence
d
9000V
±)\n&,
"hinged ends," &c, e-a:
/i2
?=.738. Hence for the 3 braces, m:
+4=1;
h%
2w(cos. 2/2 + -ym) = 46879(.477 + .738)
= 56,958
Also
Wt cos. 22' = 31280X. 477 = 14920
For the vertical members cos. 22/=^l
Now summing the results, we should
have according to the rule of art. 98,
Wc =WV +Wt cos.2i + Wb (cos.2iy?il
But the numerical values give,
Wc = 74947<14336-»-14I10 + 56958
= 85404.
104. With a less height Wc would be
larger. Let us then try A=27 ft.
It is far more direct now to compute
Vol. XIX.— No. 2—11
ay
n b 393
29 and —. — — — .
b' 406
We find, cos. 2 £=.448.
Apply eq. (14) again to the new
weights :
W'c =77723 (13824 + 29000X.448
+ 44455(.448 + . 706) = 78117
The truss may be one or two-tenths of a
foot lower there for economy. The
amount saved though is not worth the
computing, for in the change from a
height of 28' to one of 27' the amount
saved is only 740 lbs. as we find from
the above.
The time may more profitably be
spent in ascertaining the best diameters
of compression members for economy,
regard being had to the castings and
pins at the same time.
105. For the Whipple through truss,
Fig. 9, we get from the table, art. 85
Wc = 76208
Tie Be X cos. 2 £=6064x.477 = 2892
(Other ties and counters) X cos. 2if
= 36000 X— .174= — 6264
.-. 2tVt cos. 2i= — 3372
Regard b as constant for posts F/", G^
v Wv=B6 + F/r+G^=7i93
Also Wp =Cc + D5+Ei=17106
162
VAN NOSTRAND'S ENGINEERING MAGAZINE.
For these posts-= = 34, and for a "one
1 r
pin end," c —2 = ^Jqq ^and Wp (cos. 2i
+ m) = 17l06 (1+ff + H) = 34469
For the brace B«, we have as before,
//A2
Wb(cos. 2^+(t) w) = 20495(.477 + .738)
= 24901
Now from art. 98 we should have for
economy
Wc = 2wt cos. 2z + Wv + Wp (1+m')
+
Wb (cos. 2^ + (- ) wi)
whereas we find,
Wc = 76208>— 3372 + 7193 + 34469
+ 24901 = 63191
Wc is too great, hence the height should
be greater. A height of 29 feet may
now be tried.
The influence of the diagonals is very
small in our equation, since tan dBb=
50° or nearly 45° (art. 92). In a similar
manner it is found that the height of the
Whipple Deck Truss should be increased
to 29 feet.
106. The Pratt Truss, through bridge,
was next computed, for same span,
loads, No. panels and height (28') as be-
fore. The strains have already been
given. The end brace was inclined, as
in Fig. 9. Using the lettering of that
Fig. the posts Ce, T)d were given a di-
ameter of 12"; the other of 8" to 10",
the end brace and chord as before.
On making out a " Bill of Materials,"
the total weight of bridge was found to
be 333,800 pounds.
From the table of weights,
Wc =75,095 pounds.
Ties and counters =Wt = 36914,
also cos. 2i=A1*I
Wv =B6 + Ke+Iy+G^=18654
(b constant)
End brace, Mb =20495 (as before)
Posts -S^1=WP= 18174.
I
For these posts
d
28 and,
Wp (cos. 2i + wi') = 18l74(l + ^ + 1)
= 33374.
Then for economy we should have
Wc = Wt cos. 2t + Wv + Wb
(cos. 2i+-^m )+Wp (1+m).
Actually we find,
Wc = 75095<17608 + 18654 + 24901
+ 33374 = 94537
The height is too great, /i=26 may be
tried.
107. On computing, by eqs. (11) and
(12), the new weights of the Whipple
Truss for a height of 29' and of the
Pratt Truss for a height of 26', we find
a saving in the former of 544 pounds,
and in the latter of 714 pounds over the
weights of the respective trusses 28'
high.
From eq. (14) we also ascertain that
the Whipple Truss, for the diameters
take?}, might have a height of -^ foot,
say over 29' with economy. The Pratt
has within a tenth of a foot of the most
economical height for the dimensions
given.
Errata in July, 1878, Number. —
Page 81, art. 43 (14 + 1 J) should be
(14 + 3).
On page 82, 2d column, line 3, for
63866 lbs., read 63886 lbs.
On page 82, 2d column, line 4, for
33693 lbs., read 38963 lbs.
A correspondent of the Times writing
upon tests for diamonds says : "The
late Mr. Babinet of the French Institute,
in his 'Etudes et Lectures (Vol. 3, p.
38), has the following : 'I shall mention
a very delicate optical character that im-
mediately draws a line of demarcation
between diamonds and all colorless gems
— I mean double refraction. In looking
through a transparent stone at any small
object, such as the point of a needle or a
little hole made in a card, one sometimes
perceives the object double, as if the
hand held two needles, or the card had
been twice perforated. Such is the case
with all white or colorless gems; but
never with the diamond. Every stone,
therefore, that exhibits double refraction
is thereby excluded from the rank of
diamonds."
GEOGRAPHICAL SURVEYING.
163
GEOGRAPHICAL SURVEYING.
By FRANK DE YEAUX CARPENTER, C.E., Geographer to the Geological Commission of Brazil.
Contributed to Van Nostra^d's Magazine.
II.
THE ODOMETER.
The distances from station to station j
of the meander are measured by the
odometer, an implement of survey which, j
in some of its forms, has been long in
use in Europe, and has of late years re- 1
ceived especial attention and improve- j
ments in the reconnoissances and other j
geographical surveys carried on by the
War Department of the United States j
of North America. In this service it
has been adapted to the severe condi- j
tions of travel in a new country. It has |
been strengthened so as to withstand I
any shock or fall to which it may be j
subject. The recording apparatus is j
made so compact and simple that there
is no danger of disarrangement there.
Instead of the old laborious process of
pushing it by hand, the wheel has been !
fitted with shafts, so as to be drawn by
a mule, and so efficient is the method of ]
attachment that the odometer can follow
any route, however rough, precipitous, j
or narrow, that will admit of the passage
of a pack-mule.
In its simplest and best form the j
odometer vehicle is a solitary wheel, a
little more than a meter in diameter, or ;
about the size of a light carriage- wheel.
It is strongly constructed of the best
material, and is braced by opposite in-
clinations of alternate spokes, so as to be
uninjured by the heaviest jars and col-
lisions. A pair of shafts are attached to |
it, and into these a strong and steady j
mule is firmly harnessed by straps from
above and underneath. The vehicle is ;
close in the rear of the animal, and the j
shafts are made short and heavy, and in
this manner the wheel is preserved in a
plumb or upright position as it runs, not
swaying from side to side. The length
of the circumference of the wheel being ;
accurately known and tlie number of
revolutions being recorded by the at-
tached apparatus, it is a simple matter
to learn the distance between any two
points.
The recording instrument hangs in a
cylindrical box which is strapped to the
wheel. It consists of a mechanical com-
bination attached to a heavy block of
metal, whose center of gravity is at one
side of the axis to which it is suspended.
As it is free to revolve upon this axis it
always maintains a vertical position,
while its box turns with the wheel, and
the apparatus scores the number of
revolutions, of which it is capable of re-
cording 9900, or a distance of about
forty kilometers, when it begins anew.
USEFULNESS OF THE ODOMETER.
This detailed description of the odo-
meter is in accordance with the promise,
made in the early part of this article, to
dwell upon the novel features of this
work, even to the exclusion and apparent
neglect of others, already well-known,
which are really of greater importance.
Still it would be difficult to over-esti-
mate the usefulness and practical value
of this instrument. It requires but little
technical knowledge to use it and to
conduct the meander survey which ac-
companies it, and any person educated
in the simplest rudiments of surveying,
is competent for this kind of work.
For this reason every party of scien-
tific exploration and reconnoissance,
every preliminary survey for railways,
and every marching body of troops
should consider its outfit incomplete
without the implements of an odometric
survey. Aside from the mass of notes
and sketches that would be accumulated
by them, and the itinerary maps that
would result, in the item of distances
alone, the country would be more than
repaid for the cost of these surveys. As
a means of mensuration the odometer
will determine distances en route, as the
wagon travels, more truthfully than the
chain itself. These, being published,
are of profit, not only to the ordinary
traveler, but also to the general govern-
ment, whose agents and officials, in one
capacity or another, are constantly pas-
sing to and fro.
164
van nostrand's engineering magazine.
ERRORS OF THE ODOMETRIC SURVEY.
Nor is there any very great error in
the ordinary surveys which the odome-
ter is likely to be called upon to perform.
Having the geographical positions of
two towns forty kilometres apart, they
may be connected by an odometric sur-
vey, the plot of which can be adjusted
between these two positions so that no
intermediate points will be appreciably
out of place on a map of the usual scale.
Since this is a map for practical use and
for the public good, it fulfills its pur-
pose as well as if its distances had been
measured by the most refined methods.
The great objection to its use is the
tendency towards the accumulation of
error in an odometric meander, and the
farther it is from the known point which
is its origin, the greater is the probable
error of any position determined by it.
Therefore, in a prolonged journey, or in
a general survey of the country, the
odometric position should frequently be
verified, or checked and rectified, by con-
nection with known points. This can be
accomplished by making a station at
some point on a railway, boundary, or
other line of accurate survey ; by astro-
nomical observation, which, however, if
taken with a sextant, is often less relia-
ble than the meander itself, or by mak-
ing a meander station dependent upon
the accompanying triangulation, by
means of the three point problem. The
last method, which is by far the most
reliable, will be explained further on.
ERROR OF DIRECTION.
The meander is affected by error of
two kinds, of direction, and of distance.
The former, in its most serious nature, is
incurred in the survey of a tortuous val-
ley, whose general course must be ac-
cepted, or in crossing a timbered coun-
try, or a pathless plain, where the sur-
veyor is in a constant state of uncer-
tainty as to whither he is to go, or, tak-
ing a back sight, as to whence he has
come. Sometimes the engineer is
obliged to keep his eye on the sun and
get a general idea of the course from
that. Or, in traversing a dense forest,
he may find himself compelled to resort
to the paradox of sighting upon a sound;
that is, he allows the pack-train to keep
a certain distance in advance, and from
time to time he directs his telescope to
the tinkling of the bell which is carried by
the horse that leads the train. It must
be confessed that these make-shifts are
loose methods of survey, but they are
better than none, since they give the
prominent directions and the distances
between streams, divides, etc., and
months afterwards, when the engineer
comes to make the map and lay down
upon it the trail of that day's march, he
will find the poorest and most incom-
plete notes more reliable than his present
memory and judgment.
Even under the most favorable cir-
cumstances it will seldom be possible to
direct the telescope with greater pre-
cision than to the nearest degree, nor, as
a consequence, will it ever be worth
while to record any fraction of a revolu-
tion in the odometer. A road does not
usually change direction by an abrupt
angle, but by a gradual curve, and the
bearing is made approximately tangent
to that curve. Or, in the survey of a
stream, it is not known on which side
the trail will run at some point a kilo-
meter in advance, and so the approxi-
mate center of the valley is accepted.
But if there should be a solitary tree,
bush, house, rock, or other prominent
object fortunately situated for a station,
the course will be made closely tangent
to that, a reading of instruments will be
taken upon arriving there, and, going on
to the next station, the engineer will
take a back-sight to the same point. In
general the system of back-sights will
be found more satisfactory than that of
foresights, as it is easier, on a strange
route, to tell whence you have come than
to decide where you are going.
ERROR OF DISTANCE.
This error of direction, it will be seen,
is thrown by the law of chance alter-
nately to the right and left of the true
line, and so has a tendency in its elements
towards mutual compensation, and in a
measure it corrects itself. But not so
the error of distance, which is always
plus, and cumulatively so. The test of
the odometer wheel, by which its num-
ber of revolutions per kilometer is ascer-
tained, is made upon a level surface and
along a staked alignment, giving a re-
sult almost absolutely correct. In prac-
tice, however, the vehicle climbs acclivi-
ties of every grade, tacks hither and
GEOGRAPHICAL SURVEYING.
165
thither as it follows the trail up the
mountain, winds incessantly in its route
through the forest, and is disturbed by-
frequent jolts and collisions along the
rocky flow of the canon. In a theo-
retical traverse the straight line between
any two stations is determined, but in an
odometer survey the measuring imple-
ment usually follows a beaten path, and
the route distance, by road or trail, is
rarely the shortest distance between two
points. Hence, an " overrun " in its
record, which can only be remedied, and
that approximately, by the judgment of
the surveyor, who is taught by experience
to estimate very closely the surplus in a
given run, and who applies a correction
accordingly.
Still, to such perfection has the odo-
meter survey been brought, that it is a
common occurrence for a skilled worker
to meander a closed circuit of one hun-
dred kilometers, and plotting the route,
to find the plot also close within a small
fraction of a kilometer. Even this error,
being judiciously distributed in the pro-
cess of adjustment, different weights
being assigned to different runs, accord-
ing to their probable accuracy, may be
reduced so as to be practically imper-
ceptible.
OCCURRENCE OF MEANDER STATIONS.
No general rule can be given for the
frequency of meander stations, but in
ordinary country they will average per-
haps one to the kilometer. In this all
will depend upon local circumstances
and exigencies. In the survey of a long
and hidden valley, affording no opportu-
nity for checks, especial care must be
taken to preserve the integrity of the
meander, and the stations must be espe-
cially frequent; but in a survey by a
direct line across the plain two or three
stations a day may be sufficient. In a
winding path up a mountain side a
dozen stations may be necessary if there
are no chances for checks; but if the
ends of the trail, at the top and bottom
of the mountain, can be located by the
three-point problem, the intermediate
route can be neglected, being, at most
sketched in by the eye.
• There are two considerations to govern
the occurrence of stations; first, to pre-
serve the continued accuracy of the sur-
vey, and second, to note the local
geographical features which may be
encountered. For the latter purpose
stations will be made at the center of
every village, at every country-house of
importance, at the crossing and diverg-
ence of streams, roads and trails, at the
opening of a valley, at the foot and
summit of a mountain, and at the
many other geographical vantage-
grounds which the practical engineer
will know how to select. But in this, as
in the other departments of the survey,
too punctilious zeal may defeat its own
interests by causing delay, and the sur-
veyor who is too scrupulously exact in
the forenoon may have to virtually
abandon his task in the afternoon, in
order to reach a suitable camping-ground
by night.
SCOPE OF THE MEANDER SURVEY.
The zone of country considered from
a meander line may extend to the
farthest visible point, as a series of sights
upon a mountain even twenty-five kilo-
meters away will give its position to a
close approximation; but its principal in-
tent is the preparation of a narrow route
map, the areas encompassed by whose
windings will be filled in from the topo-
graphical stations. Since, from its nature
and narrow scope, it is fuller and takes
cognizance of objects more minute than
can be noticed in the other systems, in
this the engineer is liable to a charge of
partiality, reproved in the early part of
this article. But this is not partiality in
one field at the cost of neglect in
another, and the greater excellence of
this work is so much clear gain. More-
over, since the meander is usually by
way of roads of frequent travel, and
since a map is useful, and should be ex-
cellent, exactly in proportion to the num-
ber of people who are guided by it, it is
well that the meander plot should excel
in completeness those almost inaccessible
parts which will never be seen except by
the hunter or bandit.
MAKESHIFTS IN THE SURVEY.
In a forced march of forty kilometres
or more, the meteorologist and odometer
recorder, the safe carriage of whose im-
plements requires a slow and steady gait,
may proceed at a walk after taking their
readings at a meander station, which task
will occupy them but a few minutes,
while the surveyor lingers behind to make
166
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the necessary sketches and observations,
and then, riding at gallop, overtakes his
comrades before the next station is
reached. Many such shifts as this are
known to the practical and energetic
geographer, who learns to emancipate
himself from too close dependence on the
text-books of surveying, some of whose
rules are very common-place and pedan-
tic, and brings into play his powers of
ingenuity and invention, to adapt, himself
to the peculiar circumstances by which
he may be surrounded. If he finds him-
self alone, out on some trip of hasty
reconnoissance, or on some hunting ex-
cursion on which he could not carry both
rifle and transit, he draws from his watch
pocket an aneroid, and from his saddle-
bags a pocket compass or an altazimuth,
and his equipment for survey is com-'
plete; as for distances, he can estimate
them, or determine them by the time
they take, calculating at the rate of five
kilometres an hour, or, better still, by
counting the steps of his horse and allow-
ing six hundred double paces for a kilo-
metre.
In a geological survey of Brazil very
much of the travel* and exploration is
necessarily done by water, as the outcrop
of the various formations is most favora-
bly shown upon the banks of the rivers,
along which there is frequently no passa-
ble route by land. Here the stadia may
be used, provided there are two or more
boats in the party, or, in the less import-
ant instances, the methods of obtaining
distances by estimation or by time would
have to suffice. In either case the sur-
veyor should lose no opportunity to
emerge from the trough of the stream,
or to ascend some eminence, and insure
his position by observations upon three
or more known points. Should these be
wanting, he should resort to the sextant
and to its use in astronomical determina-
tions.
Since the attention of the geologist is
in great part absorbed in the duties pe-
culiar to his profession, he cannot usually
carry any but the lightest and most con-
venient implements of survey, and since
these are amply sufficient for his geologi-
cal notes of dip, strike, trend, etc., it is a
matter of expediency to make them an-
swer for his geographical work as well.
With the engineer, however, there rarely
comes a necessity for being separated
from his portable transit, which admits
of being firmly set on its tripod, and from
which angles, either horizontal or verti-
cal, may be accurately read to the near-
est minute. And in the general geo-
graphical plan it is wise to deprecate as
far as possible the employment of unreli-
able pocket instruments, or of the devices
for learning distances that have been de-
tailed above. Since nothing is to be
gained in time by their use, and very
much may be lost in accuracy, the engi-
neer should teach himself to consider,that
any method less complete than that of
the portable transit and odometer is but
a temporary expedient and makeshift,
serving an excellent purpose when all
other means fail, but not to be relied
upon as a permanent constituent of the
survey.
CO-OPERATION OF THE TRIANGULATION
AND MEANDER.
While the meander survey is an ex-
cellent apprenticeship for the young en-
gineer, it should not be despised, as an
occupation, by even the director of the
triangulation. Humble as it is, it per-
forms a task in the geographical plan
which no system of triangulation can be
relied upon to perform in a rapid work
of this nature. It enables the survey to
reach any point, however remote and se-
cluded, and to determine its positions it
makes the map complete in all of the
details which are so useful to the trav-
eler; and as an agent in what we may
call the practical, or economical branch
of geography it is without an equal.
It is dependent upon the triangulation,
it is true, but then the dependence is
mutual. The full benefit of either can
only be secured through the co-opera-
tion of the two. As without the trian-
gulation the map is unreliable, so* with-
out the meander it is incomplete. To
use a homely illustration, the triangula-
tion may be compared to the framework
of the dwelling, and the meander to the
intermediate filling of wall or other sub-
stance which makes the house habitable,
and is a shelter to the inmates. This
frame, if its lines are true and its angles
correct, is a beautiful thing for the arti-
san to contemplate, but without its com-
pletion of walls and furniture, it is of no
real benefit to the world. In the same
manner a bare triangulation scheme may
GEOGRAPHICAL SURVEYING-.
167
be an interesting study to the geographer
himself, but to the traveling public and
the people at large, it possess neither
interest nor value. On the other hand,
as the frame of the house is an absolute
necessity to it, securing and sustaining it
in its proper proportions, so is the trian-
gulation the rigid frame work of the
map and the skeleton to which the use-
ful data of the meander are attached.
CHECKS BT THE THREE-POINT PROBLEM.
Since the meander is from its very
nature so hasty and loose, the system of
frequent checks can alone make it relia-
ble, and at intervals of every few kilo-
metres, and especially at the crossing of
divides and other eminences from which
there is a broad scope of country visible,
connection should be made with the
triangulation. Each of these stations
then becomes a new initial point, at
which the survey begins afresh and the
error again begins to accumulate.
This rectification is accomplished by
the use of the three-point problem, a
geodetic determination which, as a
means of locating topographical stations,
and as a connecting link between the
meander and the triangulation, is of the
highest importance in geographical sur-
veying. Having three triangulation sta-
tions in sight, and favorably situated, it
is possible for the observer to determine
his position in a few minutes of time
and by the simple operation of reading
the two angles included by those three
stations. From these and the data per-
tinent to the triangulation stations he
can compute his distance from them, and
hence his present latitude and longitude.
Or, plotting these angles from any cen-
ter on a piece of tracing cloth, he can
lay this upon the projected map and
swing it around until each of the three
plotted rays covers its proper triangula-
tion point, when this center will indicate
the position of the three-point station, as
it is called. For this graphic determina-
tion not only three points, but four, and
even more, if they are visible, should be
observed, as a greater number facilitate
the operation and insure the accuracy
of the result.
This method of trilinear determinations
cannot be introduced too often. A
three-point station in the streets of a
settlement, at the forks of a road, or at
the end of a mountain range, will locate
these important places, and in camp,
even in the center of a broad and vacant
plain, there is no more profitable man-
ner in which the engineer can spend his
leisure time, before or after dinner, than
by making a three-point station there
and determining his position. Every
camp thus fixed is a new and reliable
origin at which the meander of the next
morning will begin.
A SURVEY BY THREE-POINT STATIONS
ALONE.
In some cases a ^successful meander
may be carried on by three-point sta-
tions alone, when all other means would
fail. Take, for instance, the rugged,
shores of a lake or bay, which are inac-
cessible except to a man on foot or in a
boat. In the mountains on the other
side of the water a series of triangula-
tion stations stand up in full view. By
means of these the engineer, working
his way, transit in hand, from bay to
bay, and from point to point, along the
water's edge, makes three-point stations
at all prominent changes of curvature,
and, sketching in the intermediate shore,
he determines its line by tangents and
intersections, and thus secures a good
survey of the coast. If there are islands
out in the water they may be surveyed
in the same way.
If the engineer was confronted with a
piece of geography like the bay and
islands of Rio de Janeiro, and if there
were no roads along the beach to make
direct linear measurements feasible, he
could extend his triangulation to include
all of the prominent peaks in the vicinity,
and then, by means of three-point sta-
tions, he could rapidly trace in the shore-
line. As the surroundings of Rio are so
broken and irregular, the triangulation
points could be made so numerous, that
it would be difficult to find a spot on the
beach, or mainland, or island, so secluded
that some three of these stations would
not be visible from there.
THE MEANDER PLOT.
Every three-point station, as well as
every other meander station, should par-
take more or less of the nature of a regu-
lar topographical station; that is, contour
sketches should be kept constantly on
the plotted page as it progresses, and a
continuous panorama of profile views,
168
VAN NOSTKAND'S ENGINEEEING MAGAZINE.
drawn in a separate portion of the book,
should accompany the survey, so that,
as some geographical features are left in
the rear, others may be introduced in
advance.
As from one topographical station to
its neighbor, so every distance from one
meander station to the next should be
considered a base to be used in the loca-
tion of points useful in the structure of
the map. The longer this base, the more
distant may be the range of these views.
In case several meander stations inter-
vene between one observation and the
following, this total intermediate dis-
tance becomes what is called a broken
base, but it is none the less useful for all
of that. The above considerations will
influence the engineer in his choice of
stations, which will always be situated in
such positions as may offer the best ad-
vantages for the accumulation of what-
ever information he most needs.
THE DECLINATION OF THE COMPASS
NEEDLE.
The variation of the compass needle,
or, more properly, its declination, will be
carefully watched throughout the sur-
vey, and determinations of its angle will
be made from time to time ; these will be
more than usually frequent wherever
there is suspicion of some attraction im-
mediately local, arising from the presence
of magnetite or other ore of iron, basaltic
rock, or other disturbing influence. These
determinations are important, not only
in the reduction of the meander notes
taken in this vicinity, but also for the
practical use, both present and future,
of the country at large. In addition, their
results will aid the general cause of sci-
ence in its investigation of the laws of
terrestrial magnetism, and in tracing the
course of isogonic lines around the world.
At every triangulation, topographical,
and three-point station, the observer
will note the direction of magnetic
north, as indicated by the pointing of
the compass needle. If his instrument
has a double movement in azimuth, as
all should have, it is well, for the sake of
convenience, to first set the zero of the
graduated limb upon the same point of
the vernier plate, by the upper motion,
and then, by means of the lower move-
ment, bring the north end of the needle
to the zero of its circle. His initial
entry in his note-book will then be
"Magnetic North, 0° 00' 00"." This
direction of the telescope being referred
to some line proceeding from here,
whose true azimuth will be found by
subsequent computation, the magnetic
azimuth or declination of the needle at
that place will be determined; it will
simply be the difference between the true
azimuth of the line, reckoned from the
north point of the horizon, and its ap-
parent azimuth, or the vernier reading
which he enters in his notes.
BY DIRECT ASTRONOMICAL OBSERVATION.
The declination of the needle will also
be determined directly by astronomical
observation in the evening at camp. For
this purpose the engineer will select such
nights, clear and still, as may appear to
him most favorable, and such camping
places as may most urgently require this
information. A star as near as possible
to the pole will be chosen, as, from its
greater declination, an error in the lati-
tude of the observer's place, and, from
its slower motion, an error in the time
of the observation, will result in less
serious errors in the azimuth; and the
smaller the polar distance of the star, the
more convenient will be the observation
and the computations which follow, and
the more exact is the result likely to be.
In the northern hemisphere CC Ursoe Mi-
noris, or Polaris, is almost always used,
as it is at present only about 1° 20' from
the pole, and it possesses the additional
advantage of a brilliancy of the second
order. But south of the equator there
are no available stars so favorably situ-
ated as this. The most southern one of
any considerable size is j3 Hydri, of the
third magnitude, whose polar distance is
a little more than twelve degrees.
This would have to be accepted in a
survey of this nature in preference to
any of the less brilliant stars of greater
declination, as the observations would
have to be made frequently by engineers
of little astronomical experience, and
with instruments not especially adapted
to this kind of work. Indeed, it might
be necessary at times to use the small
meander transit for that purpose; and it
is seldom that the telescopes of even the
theodilites for triangulation, as now con-
structed, are provided with the hollow
rotation axis requisite for a proper illu-
GEOGEAPHICAL SURVEYING.
169
mination of the diaphragm, without
which it is difficult to see both cross-
hair and star, unless the latter is of con-
spicuous magnitude.
Knowing, at least approximately, the
latitude of the place, and also the decli-
nation of the star and its hour angle at
the time of observation, its azimuth
angle from the south point can be com-
puted. But as the hour angle depends
upon the local time at that place, and
there is great room for error there, the
observer, unless he has full confidence in
his ability to make an accurate time-de-
termination, should find the approximate
minute of the star's greatest elongation,
and follow it with the transit thread
until it reaches the dead point in its
azimuth motion, where it seems to stop
a few moments between its advance and
retrogression. Then, being at its
greatest elongation, the sine of its azi-
muth angle is equal to the cosine of its
declination divided by the cosine of the
latitude of the place.
Should the star /3 Hydri not arrive at
its east or west point at a convenient
hour, as at certain seasons of the year it
will not, the star Canopus, differing in
right ascension about six hours, or OC
Trianguli Australis, of about sixteen
hours greater right ascension, may be
employed. These are respectively of the
first and second magnitude, and hence
are very well adapted to this purpose,
but, owing to their greater polar dis-
tances, it would be necessary, in their use,
for the observer to be especially sure of
the correctness of his latitude.
The sun is not usually available for
determinations of azimuth or time, as
the engineer is generally upon the march
throughout the day. The use of a star,
however, admits of greater precision in
the observations, while the resulting
computations are less complicated, and,
in the case of an azimuth determination,
a south star is doubly convenient from
the fact that its two daily elongations
always come above the horizon, and
whichever one occurs most opportunely
may be used; or it may be possible at
times to observe both, in which case it
becomes unnecessary for the engineer to
know his latitude. The same difficulty
of latitude, may also be avoided by the
method of equal altitudes of a star, taken
at several hours before and after its
meridian passage; the middle point be-
tween the two corresponding azimuths
will be upon the meridian.
THE METEOROLOGIST AND HIS INSTRU-
MENTS.
In all of his travels the meteorologist
will be the constant companion of the
engineer, so as to be prepared to take
observations at any point that the latter
may designate. At the beginning of the
field season he will be furnished with, at
least,two complete sets of meteorological
instruments, to be carried by himself and
by others who may be appointed to as-
sist him. Each set will be composed of
a cistern barometer, an aneroid, maxi-
mum and minimum thermometers, pocket
thermometers, and a psychrometer, con-
sisting of two similar thermometers, one
with its bulb capable of being moistened
by the capillary attraction of a loose cord
of cotton filaments leading to it from a
cup of water, and the other dry, as in the
ordinary instrument.
Prior to taking the field he will com-
pare these barometers by a series of
readings extending through several days,
with some standard barometer whose er-
ror is known, in order to obtain the in-
strumental errors of the instruments at
hand. Throughout the season, also, he
will lose no opportunity for comparisons
with any reliable barometers that may
be encountered, as well as for frequent
comparisons between these two. In this
manner the time of any possible disloca-
tion of the scale, or other source of error,
will be determined.
As in the rough and rapid travel of a
geographical survey, there is great lia-
bility to break the fragile glass tube
which contains the heavy mercurial col-
umn, an extra supply of barometer tubes
and mercury should be transported with
the party, and also an assortment of
tools and material for the filling, boiling,
and fitting of a fresh tube. This is a
j delicate and difficult task, but it is one
| in which every meteorologist should be
! proficient. As full instructions for the
j use and repair of meteorological instru-
ments have already been prepared by
the Commission, it is needless to repeat
them here.
METEOROLOGICAL OBSERVATIONS.
At every station of the survey, the
meteorologist will read from his instru-
170
VAN NOSTRAND'S ENGINEERING MAGAZINE.
ments the data from which the elevation
of that point may be subsequently com-
puted. Nothing more is then needed
for the precise determination of that
station's position. The engineer has fixed
it in latitude and longitude; the mete-
orologist, in its altitude above sea-level.
The meteorological data will be more or
less comprehensive and will be read from
instruments more or less reliable, accord-
ing to the geographical importance of
the place at which they are taken. The
more frequent the readings, and the
more prolonged the series, the more
trustworthy will the resulting mean be,
and the less liable to be materially
affected by errors of observation, and
by those erratic fluctuations to which the
barometer is subject, owing to the con-
stantly varying atmospheric currents and
other disturbing physical conditions to
which it is exposed, and whose effect
cannot be entirely eliminated by any
formulas that it is possible to devise.
Beginning at the point t)f outfit'
which, on account of the work of pre-
paration and the measurement of the
base-line, may be occupied some weeks
or a month, hourly readings will be taken
throughout the clay and night for as
long a time as possible. The cistern
barometers will be read, as the height of
the mercurial column is the basis upon
which all barometrical determinations
rest. The attached thermometer will
be read, to learn the temperature of the
mercury, and hence what correction
must be applied to reduce it to the
freezing point, at which all barometrical
heights are compared. The isolated
thermometer will give the temperature
of the surrounding atmosphere, to be
used in determining the mean tempera-
ture of the stratum of air intermediate
between this and the reference station.
And the psychrometer will reveal the
amount of aqueous vapor in the atmos
phere, and the influence of its pressure
upon the height of the column of mercu-
ry. In addition to these, note will also
be taken of the direction and force of the
wind, the condition of the sky, the proxi-
mity of storms, and other atmospherical
phenomena, as this information may
give the key to some abnormal baro-
metric oscillation which would otherwise
have to remain unexplained.
HORARY AND ABNORMAL OSCILLATIONS.
The hourly observations will be con-
tinued throughout the day and night for
the purpose of determining the amount
of the horary oscillation at that place.
This horary oscillation is a somewhat
regular rise and fall of the barometer,
occupying a period of twenty-four hours.
The range of this fluctuation in some
parts of the world is so great, that its
effect upon the mercurial column may
equal that which would be produced by
a change of fifty meters in altitude. It
is such that, if the successive heights of
the column be represented graphically
by a curve, this curve will show two
daily maxima and minima, occurring at
intervals of about six hours, the morning
maximum being attained at about ten
o'clock A. M. This horary curve, as it
is called, varies with the latitude, alti-
tude, and climate of a place, as well as
with the different portions of the year.
The value of the horary variation for
any hour of the day is revealed by a
study of the prolonged series of observa-
tions at that place, and may be assumed
to be the same for all observations taken
in the vicinity of that station" and in the
same season of the year.
The barometer is also influenced by
the abnormal oscillation, apparently re-
sulting from the progress of great atmos-
pheric waves across the country, affect-
ing the mercurial column by a gradual
rise of several days, followed by a period
of subsidence of about an equal duration.
The effect of this disturbance can be
eliminated, approximately, by taking the
difference of the barometric readings at
the beginning and ending of any one day
of its rise or fall, and considering this as
its amount for that twenty- four hours, a
proportional part of which will be its
value for one hour.
DETERMINATION OF HEIGHTS.
To obtain the altitude of the first
station of the survey, a mean of the cor-
rected heights of the mercurial column
is compared with a corresponding mean
of the same hours of the same days at
some permanent station, whose elevation
above the sea is definitely known, as, for
instance, the Imperial Observatory at
Rio de Janeiro. This, by a process of
computation, gives their difference of
GEOGRAPHICAL SURVEYING.
171
altitude, and hence the total elevation of
the point in question.
Now, making this point of outfit a
reference station, at which an observer is
left with meteorological instruments to
be read at stated intervals throughout the
day, the party takes the field, and the
traveling meteorologist reads a series of
barometrical and other observations at
the first camp and at all others to which
they may come during the season.
These will be compared, as before, with
synchronous* observations at the refer-
ence station, and the differences of alti-
tude will be calculated. At every topo-
graphical station, and station of import-
ance along the meander survey, such as
villages, f azendas, mines, mountain passes,
divides, etc., and at all other points that
may be designated by the engineer, the
meteorologist will read the cistern baro-
meter, the watch, the thermometer, and
the psychrometer,vand, for the purposes
of comparison, the aneroid barometer as
well. These isolated observations will
also be referred tp the main barometrical
station at a distance.
But, on the occasion of the ascent of
a mountain peak from a fixed camp, bet-
ter results will be obtained by consider-
ing the camp a reference station in the
determination of the altitude of the
mountain. This ascent will necessitate
the occupancy of the neighboring camp
for two nights and a day at least, and
perhaps longer, while the peak may be
occupied only a portion of a day, during
which time, however, there will be cor-
responding hourly observations at camp
and mountain-top. Hence the altitude
of the mountain will be most truthfully
ascertained by referring it, by these syn-
chronous observations, to the camp, and
then the camp, in a similar manner, to
the distant reference station.
HOEAEY CURVES AND EEFEEEXCE STA-
TIONS.
Whenever the party, or a portion of
* It is well to distinguish between the meanings, as now
understood, of the two words " synchronous " and '• sim-
ultaneous." The term " simultaneous " is applied to ob-
servations which are made at the same absolute instant
of time, as, for instance, upon the occultations and
eclipses of the heavenly bodies. Synchronous observa-
tions are taken at the same hour of the day, local time,
irrespective of the difference of longitude between the
two stations. Therefore, observations can be both sim-
ultaneous and synchronous only when the observers are
upon the same meridian. The word " simultaneous "
belongs especially to the province of astronomy, whilst
" synchronous " is most frequently used in connection
with the phenomena of physical geography.
it, remains stationary in camp for a few
days at a time, hourly observations day
and night will be taken to determine the
horary curve at that place; the longer
the series, the better will be the result.
Since the horary variations are constantly
changing with altitude, country and cli-
mate, it is important to have as frequent
determinations of them as can practically
be made, so that no very great distance
may intervene between the place where
a table of horary corrections is construct-
ed and the place where it is used.
For a similar reason it may be deemed
necessary to establish and sustain a sec-
ond meteorological reference station, if
the field of the season's survey should be
a wide one, or if it should vary greatly
in the atmospherical condition of differ-
ent portions of its area. No comprehen-
sive rule can be given to govern the num-
ber of these reference stations; all must
depend upon the judgment of the direc-
tor of the survey, and the resources at
his command. In general, the farther
the place of an observation from its
reference station, the less reliable will be
its result. But, as an exception, let us
take the example of a broad inland plain,
separated from the sea and its influences
by a wall of mountains, within which,
upon the plain, the reference station is
situated. In this case it may be more
justifiable to refer to this station a point
on the plain, five hundred kilometres dis-
tant, than one just over the mountains,
only one hundred kilometres away. This
is owing to the widely different climatic
circumstances of inland and sea-coast,
resulting in meteorological conditions so
dissimilar that equal amounts of pressure
cannot be relied upon as an indication of
equal thickness of the atmospheric enve-
lope.
THE ANEROID BAROMETER.
At the many stations of the meander
survey that are comparatively unimport-
ant, and that are occupied for a few min-
utes only, it will suffice for the meteoro-
logist to read only his aneroid, watch,
and thermometer. Although the aneroid
is not a reliable instrument, yet it serves
an excellent purpose where rapid and ap-
proximate work is sufficient. Since its
principal use is in obtaining profiles of
the meander routes, which will enable
the engineer to properly distribute the
172
VAN NOSTKAND'S ENGINEERING MAGAZINE.
contour lines upon his map, and since,
farther, the error of an aneroid will rare-
ly exceed the vertical distance between
two of these contours, the resulting inac-
curacy upon the plot will be quite inap-
preciable.
The aneroid is to the cistern barometer
what the meander is to the triangulation,
that is, a means of filling in, which,
while costing but little extra effort,
is productive of very valuable results.
The engineer who rejects the meander
and the aneroid because they are not
rigidly exact in their functions, will find
himself reduced to the necessity of
tracing in the roads and streams of his
map, locating many of the villages, cross-
roads, etc., and drawing in the contours
from his judgment and memory alone;
and it is safe to say that the conjectures
of the most able and trained topographi-
cal intellect are by far less reliable than
the figures of those humble instruments,
the aneroid and odometer, when judi-
ciously used.
At every camp the aneroids are com-
pared with the cistern barometer, their
scales are adjusted in compensation for
any error that may have crept in, and
the vertical element of the survey starts
from a new and true datum plane when
the march is resumed. At the end of
the day's journey, also, they are imme-
diately compared again, and the error
accumulated throughout the day is
noted, and, by a process of distribution
along the day's profile, may be reduced
to a minimum. Before and after every
side trip, reconnoissance, or ascent of
mountain, the aneroid is compared with
the mercurial barometer, and thus, by a
continual and careful watch over it, i,t
may be relied upon to give results not
seriously in error. But if left to itself
and unchecked for any great length of
time, or for any great distance of journey,
or great change in altitude, this fickle in-
strument may continue to go astray, by
a shifting of its scale, exhaustion of its
spring, or from other causes, until its
readings are hundreds of meters too
high or too low. Even then, however,
it may be of use to the geographer in
drawing in the relief of the country, as
the discrepancy is usually of gradual
growth, and the relative altitudes during i
the progress of the survey, as, for in-
stance, the height of a bluff above the
neighboring valley, are sufficiently exact
to be of much assistance to him in his
plotting.
BAROMETRICAL RESULTS.
As to the reliability of altitudes de-
termined by the cistern barometer, evi-
dences and opinions differ, but those per-
sons who are most thoroughly informed
are generally the most lenient in their
acceptation of results. Colonel Wil-
liamson, of the United States Army, who
has probably given more intelligent
study to the barometer than any other
man, has compiled a table of the maxi-
mum errors which occur in numerous
series of observations taken both in North
America and Europe. Among these are
many that exceed fifty meters in amount,
and he assumes that the barometer under
similar circumstances will be liable to
equal errors elsewhere. These, however,
are not to be considered as representing
the probable error of barometrical re-
sults, they are rather the extreme limits
of probable error, and "may be taken as
the error to which the barometer is liable
under certain rare and very unfavorable
conditions. While exact truth concern-
ing altitudes is something which no
barometer can be expected to tell, and
while it is never safe to guarantee the
accuracy of such a determination, even
within many meters, yet when baro-
metrical work is prosecuted judiciously
and systematically, as it would be in this
survey, and based upon formulas which
represent the latest and most complete
knowledge of meteorology, its tendency
is to give results that are seldom more
than a few meters wrong.
It is often difficult for the popular
mind to comprehend how an error of
meters may be inevitable in some of the
processes of barometric hypsometry.
Since the scale of a barometer may be
read to a thousandth of an inch, and that
amount of variation is supposed to cor-
respond to a change of one foot in alti-
tude, it would naturally be thought
possible to determine the elevation of a
place to the nearest foot. But this diffi-
culty will be better understood when it
is remembered that the barometrical
measurement of the difference of altitude
between two places depends upon the
determination of the weights of a column
of atmosphere at each of these stations;
GEOGRAPHICAL SURVEYING.
173
that this atmosphere is in a state of con-
stant change and perturbation, its press-
ure being modified by variations of heat
and cold, storm and calm, and the
absence and presence of moisture through-
out different portions of its extent; and
that, while some of these conditions are
quite unknown to the observer, those
that are apparent to him can be but in-
completely compensated for. There-
fore, since barometric hypsometry is not
one of the exact sciences, but is affected
by every change in the wind and
weather, any determination of altitude
that is true within a meter, is as much
a source of surprise as of gratification to
the meteorologist, who will be obliged
to confess that this closeness could
scarcely be possible without some coin-
cidence and accidental equilibrium in
the disturbing influences to which the
barometer is subject.
DIFFICULTIES IN BAROMETRIC
HYPSOMETRY.
At times men of little experience may
have to be accepted as meteorologists.
They work, perhaps, under the embar-
rassments of exposure, fatigue, and a
lack of appreciation of the responsibilities
that rest upon them. It may be long
before they can be taught to regard
those niceties of barometrical work with-
out which it cannot be truly successful;
although there is but little hope of
determining an altitude to the single
foot, yet they have to learn that this is
no reason for neglecting that thousandth
of an inch which corresponds to a foot.
Their instruments may be out of order,
owing to the hardships of travel to which
they are exposed; the readings may have
to be referred to a distant station of very
dissimilar physical surroundings; or they
may have been taken upon the top of a
lofty mountain, in a belt of the atmos-
phere with meteorological phenomena
quite different from those properties of
the lower strata of the air, for which
our formulas were framed.
These are some of the sources of error
which may have conspired to vitiate
those results which are fifty meters or
more at fault. In Brazil, however, it is
hardly necessary to anticipate discrepan-
cies so great as this, since it is a country
in which no very great change of alti-
tude is possible, violent and phenomenal
I storms are not frequent, and the atmos-
I phere is of comparatively steady tem-
' perature, and not liable to sudden transi-
tions from one extreme to the other.
BAROMETRIC FORMULAS.
Even if the observations have been
made under the most favorable condi-
tions of atmosphere, elevation and loca-
tion, and are perfect as far as human in-
telligence can make them so, that is, free
from all personal and instrumental er-
rors, there yet remains a consideration
which may materially affect the com-
pleted altitude. The same observations,
reduced by different formulas, will give
results in some cases widely different,
the discrepancy between the returns of
two well-authorized methods of compu-
I tation frequently amounting to the sum
of the real errors of both; this is ex-
emplified in the following determination
of the height of Corcovado, in which one
system of reduction gives an altitude
above the true one, and the other places
it too low.
The barometric formula is composed
of several terms, each of which is a com-
bination of some physical constants, such
as the relative weight of air and mercury,
or the variation of gravity with latitude,
and some of the barometrical data, as
the temperature or moisture of the at-
mosphere. Of these formulas, there are
two general classes, based upon the equa-
tions of Laplace and Bessel. Not only
do they differ in those constant quanti-
ties upon which all barometrical determ-
inations must depend, but also in the
presence or absence of an entire term, as
the formula of Bessel has a separate fac-
tor as a correction for the humidity of
the air, while Laplace includes the in-
fluence of the aqueous vapor with that
of temperature.
Thus it will be seen that the formula
of Laplace is more convenient, while that
of Bessel is more complete. The scien-
tific world has found it difficult to choose
between them, and while Delcros, Guyot,
and others have accepted the formula of
Laplace, that of Bessel has been adopted
by Plantamour, Williamson, and others.
But it is admitted, even by those who
are in favor of the former method, that
the constants in use in Bessel's formula,
as modified by the more recent arrange-
ment of Plantamour, are later and more
174
van nosteand's engineering magazine.
reliable than those accepted by Laplace,
and there is also a prevalent opinion
among scientists that some accuracy has
been sacrificed to convenience in La-
place's method, a concession which it may
sometimes be justifiable to make in the
application of a formula, but never in
its construction.
The advocates of each system have
published examples showing the close
accordance of their results with altitudes
determined trigonometrically or by spirit-
level. But as the number of these re-
markable coincidences is about equal on
each side, and as in each instance the
observations would have given results
considerably wrong by the application of
the other formula, they prove simply two
things; first, that they are coincidences,
and that to certain cases the method of La-
place is most applicable, while to others
that of Plantamour will yield better re-
turns, and second, that it is quite impos-
sible to devise any formula that will
yield an accurate solution of all problems
in the barometrical measurement of
heights.
Since there seems to be a preponder-
ance of evidence and a growing disposi-
tion in favor of Plantamour's formula, it
has already been adopted by the Geo-
logical Commission as a basis for its
barometrical work, and its several terms
have been developed into tables for the
convenient computation of altitudes.
After the preparation of those tables and
as a test example with which to prove
their efficacy, the height of Corcovado
Peak was determined barometrically
with the following results:
Metres.
Altitude of Corcovado, by tables of the
commission, based upon Planta-
mour's formula. 705.84
By Laplace's formula 702.15
Determined by triangulation 704.74
Metres.
Error by Plantamour's formula -f-1.10
" Laplace's " —2.59
Discrepancy between the two 3.69
The foregoing is a very creditable and
satisfactory barometrical result, and is
one more argument in favor of the use
of Plantamour's complete formula.
ALTITUDES BY VERTICAL ANGLES.
As a supplement to the barometric
hypsometry, every theodolite, whether
for meanders or triangulation, is fitted
with a vertical circle, from which to read
the angles of elevation and depression of
those points which are located by inter-
sections, in order to compute the heights
of the same. From this angle and the
horizontal distance between a'ny two
peaks, their apparent difference of alti-
tude is obtained by a trigonometrical
calculation, and then a correction is ap-
plied for earth's curvature and refrac-
tion. In the field these angles are
recorded as plus or minus, according as
the objective point is above or below the
observer's station, whose altitude is in-
variably determined by barometric read-
ings.
In this manner the heights of hund-
reds of points throughout the field of
survey are found with an accuracy
nearly equal to that of the peak from
which the angle is taken. Indeed, a
mean altitude derived from the three
angles of elevation, read from three
different triangulation stations, will give
the altitude of the point of intersection
with less probable error than that of
either of the mountains from which it
was derived.
METEOROLOGY IN THE SOUTHERN HEMI-
SPHERE.
Brazil stands almost alone as a great
civilized country lying in the Southern
hemisphere. It is comprehensive in its
latitude, reaching from north of the
equator far into the south temperate
zone. From this unique and favorable
position upon the earth's surface, as well
as from the liberal patronage bestowed
by its government upon the de-
velopment of science, it needs no
prophetic eye to see that this em-
pire is destined to become one of the
busiest and most fruitful fields of scien-
tific research. Especially is this the case
in the investigation of those great ques-
tions concerning the terrestial shape and
dimensions, and those others, still more
numerous, which from the form of the
earth, or from other and unknown
causes, vary with geographical position.
Important among the latter is the science
of meteorology, whose general laws are
not the same all the world over, but
which are largely influenced by latitude
and by proximity to either pole.
The following extract from Colonel
Williamson's valuable treatise on the
GEOGKAPHICAL SURVEYING.
175
barometer and its uses, will illustrate
the absence and the need of meteorologi-
cal observations south of the equator:
" It has been determined by actual ob-
servations, and confirmed by theory, that
the sea-level pressure varies in different
latitudes by a definite law, modified in
practice by local peculiarities of climate.
It has been found that the mean baro-
metric pressure is less in the immediate
vicinity of the equator, and it increases
towards the north to between latitude
30° and 35° where it is greatest. It then
gradually decreases to about latitude 60°,
and from there towards the north pole
there is a slight increase. In the south-
ern hemisphere, where the observations
have been less numerous, the mean
pressure seems to increase to between
20° and 30° of south latitude, when it
gradually decreases to about 42°, and
then commences a remarkable fall, so
that towards the south pole, the mean
pressure is said to be less than 29
inches."*
In the table of mean heights of the
barometer at the sea-level, given in
various works on meteorology, there are
but two stations south of the equator;
these are Rio de Janeiro and the Cape of
Good Hope. In north latitude, however,
the list comprises more than thirty
places at which this determination has
been satisfactorily accomplished, by
years of observations, and these are
favorably situated at intervals between
the equator and the pole.
Again, while the horary oscillation in
the atmospheric pressure is greatest
near the equator, and diminishes thence
each way to the poles, the abnormal
oscillation is least in regions of small
latitude, and increases with the distance
from the equator. As the latter is
the more incomprehensible and less
regular of the two, and consequently the
greater source of error, it would appear
that, in general, barometijcal work would
be most reliable in tropical regions, and
hence this system of hypsometry would
be especially applicable to Brazil. And,
in addition to their immediate and prac-
tical use in the construction of maps, the
meteorological results of a survey of the
proposed nature, taken at low and high
altitudes, at the sea-coast and in the
736.6 millimetres.
remote inland, with permanent stations
at intervals where long series of obser-
vations would be accumulated, would
form a basis upon which to establish the
general laws of barometric fluctuation
throughout this vast portion of the
Southern hemisphere.
CONTINGENCIES IN THE SURVEY.
The foregoing are the general divi-
sions and some of the novel features of
the geographer's work in the field.
While these are sufficient to carry the
survey across any ordinary country, cer-
tain districts may be encountered in
which these methods may not be easily
applicable. It is impossible, in a paper
of this nature and length, to foresee and
provide for all of the emergencies that
may arise; it is necessary for the geog-
rapher to first see his territory, and then,
if he is a true engineer, he will be able
to devise some means of survey which
will be competent to meet the difficulties,
however great they may be.
For instance, it may be asked how a
survey based upon triangulation, can be
carried across the smooth and unbroken
table-lands of a country. The answer
will be that the plains are not usually so
broad that they cannot be spanned by
the length of a triangle-side ; and,
furthermore, if there are no eminences
that can be used for triangulation points,
so much less is there need for this system
of survey. Over the smooth plain it is
possible to travel in straight lines, such
being the usual character of roads in a
level country, and since a meander by
direct routes is reliable, the survey can
proceed from one known point to the
next with comparative accuracy, tracing
in the rivers, lakes, and other geographi-
cal features as it goes. As a rough,
mountainous country is its own remedy,
furnishing a great number of advantage-
ous stations for the survey, so, with the
absence of these mountains, vanishes in
great part the labors and difficulties of
this work.
THE STADIA, OR TELEMETER.
Although the stadia, or telemeter pro-
cess, is too slow for the general prosecu-
tion of a geographical survey, there may
be occasional areas in which the previous
methods will fail, and this will suffice.
The direct linear survey of a river, by
176
VAJ5T NOSTRAND' S ENGINEERING MAGAZINE.
this means, has already been mentioned.
As another illustration, take the case of
a valley — as, for instance, the valley of
the Amazon — which is so broken with
lakes, swamps, and the many channels
and arms of the river, that its islands
and shores cannot be reached and located
by any means of direct measurement;
and where, farther, the vegetation is so
abundant and dense, that ordinarily no
three fixed points are visible from the
water's edge. Here the telemeter may
be the only instrument by which the re-
quired distances may be obtained. The
observer, establishing his instrument in
open ground, from which triangulation
stations can be seen, sends his assistant,
in a boat- or otherwise, to such points
along the water as may be in sight.
These he locates by single observations,
reading the distances from the rod held
by the assistant. Thus the telemeter
station is referred to the observer's posi-
tion, which, in its turn, can be fixed by
means of three- point observations upon
the triangulation stations of the border-
ing cliffs.
In this simple and ingenious way of
determining distances by single observa-
tions, it is necessary that the diaphragm
of the telescope of the observer's instru-
ment should be fitted with two horizon-
tal cj oss-wires, and that his assistant
should be furnished with a graduated
rod, or telemeter. Then looking through
the telescope, the projection of the cross-
wires upon the rod includes a certain
amount of the graduation. This is a
chord subtending a certain constant
angle in the line of collimation, and, by
a principle in geometry, this chord in-
creases directly with its distance from
the angle which it subtends.
THE PLANE TABLE.
With the use of the plane table, there
comes so great a temptation to go into
the details of the work, to linger over a
small area, and to finish the sheets with
a topographical completeness, that its too
general adoption will be found to retard
the progress of a geographical survey.
In addition, it is cumbersome in its
shape, offering a broad surface of ex-
posure, and for that reason is not well
fitted for service upon high mountain
stations, where the wind is strong and
storms are frequent. In its favor, how-
ever, it must be said that this instru-
ment has been successfully employed
upon the extensive geological and geo-
graphical surveys under Major J. W.
Powell, of the United States, and that
very favorable reports have been made
concerning its usefulness. The incon-
venience of its shape has been modified
in this service, the table being composed
of slats hinged together, so that it may
be folded into a small compass for the
purpose of transportation.
When, in the course of a work of this
nature, there is encountered a district
where the importance of the field will
justify a minute and laborious survey,
the plane-table will serve an excellent
purpose there. It is very useful in the
mapping of a populous district, the
suburbs of a city, a mining region, or in
the representation on large scale of a
piece of topography which is interesting
as a type of geological structure. It is
always an easy matter for the geogra-
pher to accommodate himself and his
methods to detailed surveys like the
above, and it is a mistaken idea to sup-
pose that the exploration of a province,
unfits an engineer for the topographical
delineation of a parish. In all work of
engineering there is a constant tendency
towards greater accuracy, refinement,
and detail, and it is not freedom which
the geographer enjoys, in neglecting the
minor features of the earth's surface,
but rather a necessary restraint that is
imposed upon him, to keep him from
sacrificing the important to the unim-
portant.
THE OFFICE WORK.
As for the computations and other
reductions of notes which follow a field
season of the survey, there is not space
to discuss them here, nor is there any
special need of such a discussion, as they
do not differ materially from those
which apply to geodetic work in general.
Nor are the duties of the draughting-
room greatly distinguished above the
customary routine of such office work.
This thing only, may be noticed, that
the hand to hand struggle which the
field engineer constantly sustains with
the forces and obstacles of nature blunts
the delicacy of his touch, and makes his
hand too heavy for the fine drawing
necessary in a map finished for publica-
GEOGRAPHICAL SURVEYING.
177
tion, and there should be in every office
a superior draughtsman who is accus-
tomed to the use of no heavier imple-
ment than the artist's pen.
This artistic finish is bought by some
sacrifice of accuracy, however, and be-
ween the field engineer and the final
draughtsman there should be few, if any,
middlemen to compile and replot the
work, because only the man who has
seen the country can reproduce its physi-
cal characteristics with truthfulness.
In every copy that is subsequently made
the face of the land grows more artifi-
cial and ideal; each mountain loses its
individuality of shape, and assumes a
symmetrical regularity which it does
not possess in nature; some of the nice-
ties of truthful representation are mag-
nified into exaggeration, and others are
overlooked and obliterated; the bed of
every canon grows broader in each suc-
cessive transcript; and the large hills
grow larger as the smaller ones dwindle
away. As in a popular parlor game, a
whispered story, passing current from
mouth to mouth throughout the round
of a circle, grows strange and distorted
beyond recognition, so in the successive
reproductions of a map by strange
hands, it loses its photographic truth of
execution as the idiosyncrasies of the
various draughtsmen are wrought into
the plan. Finally it comes to represent
a country that is unnatural in its regu-
larity, made not so much by the acci-
dents of nature as by the design of
man, and moulded by the rules of a uni-
form and rigid geometry.
PLOTTING THE NOTES.
It is necessary that each engineer
shall plot his own notes, as he alone is
familiar with their arrangement through-
out his books, and only he is able to de-
rive the full benefit from them. There-
fore during the office season he will be
engaged upon a contour plot of the area
which he has surveyed during the pre-
ceding half of the year. Here he will
collect and compile in graphic shape all
of the information which lies scattered
throughout the dozen note and sketch-
books which represent his labors in the
field. Upon this map fine drawing will
not be so essential as truthful representa-
tion and the utmost accuracy of position
that can be attained from the material
Vol. XIX.— No. 2—12
at hand; an inaccuracy that is barely
apparent upon the paper will correspond
to a very large error in the field, and so
a moment's oversight in the office may
invalidate the scrupulous care of a day's
or week's work upon the survey.
These sheets will be the basis of all
the maps of the survey, no matter in
what shape they may be published, and
hence the urgency of having them correct
in all of their positions, statements and
figures, and so complete as to include
every detail upon the pages of the
sketch-books, down to the shape of a
mountain-spur or village, or the presence
of a spring of water or dwelling place.
As the expense of sustaining an engineer
in the field is at least double the cost of
his office-work, he should confine himself
to what is absolutely necessary in the
collection of his notes, and then utilize
even the least of these in his subsequent
plotting and development of them.
CONTOUR PLOTS.
The plots will be constructed in con
tour lines, as that is the only method in
which the engineer can give precise ex-
pression to his information and impress-
ions concerning the heights, slopes, and
forms of the country that he has sur-
veyed. While a map executed in
hachures would be more artistic and
more pleasing to the eye, it cannot be
made so mathematically invariable in its
conveyance of ideas, that is, it cannot be
made to convey the same ideas to all
persons; the bluff that would seem high
to one observer would seem low to
another, and the depth of shade that
would represent a steep gradient to one
draughtsman would stand for a moderate
declivity to another, according to their
peculiarities of judgment, or to the
different schools of drawing in which
they had been educated. The most
skilled cartographer, with one of the
best of hachure maps before him, would
find it difficult to estimate the angle of
any mountain slope, or to tell which of
two neighboring peaks was the highest,
unless their heights were given in figures.
In a glance at a contour plot, however,
he could count the excess of lines in one
of these mountains, and so compute its
superior altitude; or note the number of
lines in a centimeter of space, and so
determine the gradient of the earth's
178
VAN NOSTRAND'S ENGINEERING MAGAZINE.
surface there. For this reason the con-
tour plot is the only true basis from
which subsequent maps can be made;
then, no matter how many field engi-
neers may contribute to this work, their
reports will all come to the compiler and
final draughtsman, written in the uniform
language of lines at regular vertical in-
tervals. Otherwise, if the plots were in
hachures, this draughtsman would find
it well-nigh impossible to so assimilate
them that his finished map would not
reveal traces of the many different hands
from which it originated.
FINAL MAPS.
Unless the contour lines are so numer-
ous and close together as to produce
striking contrasts of light and shade as
the slope varies, this map has no mean-
ing to the popular eye. The ordinary
observer sees in it only a maze and con-
fusion of lines, of whose design and
importance he is ignorant, and so it is of
no assistance to him. Therefore, since
maps are usually published for the in-
formation and guidance of the people at
large, it is wise that they should be
drawn with hachure shading, which
gives a more intelligible but less precise
picture of the country. In the construc-
tion of this, the contours of the engineer's
plot are so many guide-lines to the
draughtsman, who graduates the light
and darkness of the shade to accord with
the divergence or approach of these
wavering lines.
In addition to these a map in contours
may also be issued for the use of engi-
neers, the projectors of railways, and,
more especially, as a basis of the geo-
logical and resource charts, to which
this system is peculiarly adapted, as its
lines of equal level are of great assist-
ance in determining the extent of the
various formations, and for depicting
those areas of vegetable growth which
are bounded by fixed limits of altitude.
The dip and strike of a bed of uniform
slope being given at any one point of its
outcrop, it is an easy matter to trace
upon this map its line of reappearance
upon the farther side of a mountain-
range, or at any other point at which it
may be exposed again. Or, by counting
the lines of vertical equi-distance, the
geologist learns the thickness of the vari-
ous strata, the extent of a fault, or any
other fact in geological dimensions.
REVIEW OF THIS METHOD OF SURVEY.
In this paper the writer is at a disad-
vantage in appearing to advocate inac-
curate methods, and perhaps, at times,
actuated by a desire to give a perfectly
frank and honest expose of the subject
under discussion, he has magnified the
amount of inaccuracy to which the
operations described in these pages
would be liable; at all events he has
been very liberal in his allowance for
probable error. Indeed, to those who
have been in the habit of reading, and
believing, barometrical altitudes that are
given down to the tenth of a foot, or
sextant determinations to the hundredth
of a second, it may appear unpardonably
liberal to allow for an error of meters or
seconds in these classes of work, and
perhaps to some it may seem indicative
of professional unfitness in the engineer
who would acknowledge the liability of
such. But while results like the above
are frequently published, their authors
would be either sciolists or charlatans if
they were to claim that they were abso-
lutely reliable down to those small
fractions; it is often the custom among
the most conscientious and intelligent
engineers to make their reports in that
elaborated form, since those are the
figures at which their computations
finally arrived, and hence there are cer-
tain weights of probability in their
favor.
In like manner, in the computations of
a survey of the proposed nature, it would
never be allowable to neglect or throw
away any odd figure or fraction, on the
plea that it was probably exceeded by
the error of the whole. By following
this system, not only are habits of accu-
racy inculcated and sustained among the
assistants of a survey, but the closest
possible approximation to the truth is at-
tained.
In the ordinary branches of his profes-
sion, habits of rigid precision, at what-
ever cost of time and money, are the
best recommendations for an engineer.
In a geographical survey, however, to
enforce this rule beyond the triangula-
tion, upon which the integrity of the
whole depends, and to continue it in full
force throughout all of the subordinate
GEOGRAPHICAL SURVEYING.
179
branches of the work, would be to make
such a survey impossible in Brazil, owing
to the enormous expense that would at-
tend it. Viewed theoretically, the best
of maps, even those produced by the
tedious processes of the European topo-
graphical surveys, are but approxima-
tions to the truth; the question now
arises as to how close it is profitable to
bring this approximation. Viewed prac-
tically, the maps that would result from
the proposed system of survey would be
seldom, if ever, in error to a perceptible
degree, and it would seem that this is
the limit of accuracy beyond which this
country cannot well afford to go.
To condemn a method of surveying
because it is not absolutely accurate
would be to condemn all of the survey
of the world, and especially all of the
systems of ordinary land surveying,
which are so faulty that it is very sel-
dom that a purchaser of land does not
get either considerably more or less than
he pays for. Still, that has not been
deemed sufficient reason why all buying
and selling of real estate should cease
until its boundaries could be determined
by the instrumentality of such rods, com-
pensated for temperature or packed in
ice, as are used in the measurement of
geodetic base-lines. In one respect the
proposed system is far superior to the
land survey, as it is founded upon the
principle of triangulation, which, secur-
ing it in its true proportions, prevents
any great accumulation of error. In the
United States of North America, where
surveys of this nature are in active and
successful operation, it has been earnestly
advocated that the triangulation of the
geographical survey should be made the
basis of the land survey, the different
triangulation stations serving as initial
points from which to run the land bound-
aries, and it is very probable that, with-
in a year or two, this plan will be
adopted there.
There are different degrees of accu-
racy, each adapted to the end which it is
intended to serve; this degree, explained
here, is sufficient for the rapid prepara-
tion of a very useful and complete
geographical map. It would not suffice
for the measurement of an arc of the
meridian, such as has been proposed for
this empire. That is a work in which
ho error, however small, that is not be-
yond the cognizance of the human
'• senses and judgment, can be excused or
j overlooked. To publish a wrong result
I here would be not only a national dis-
grace, but a misfortune to the whole
world, as it is upon the shape and dimen-
sions of the earth that many of our
geodetic and other scientific formulas
rest, while it is from the same source
that the world derives its standard unit
of length, by which the interests of all
civilized people are affected. Or, if
Brazil were prepared to enter into that
honorable rivalry in geodetic work, in
which some of the older nations are en-
gaged, each seeking to produce instru-
ments, methods, results, discoveries, and
developments that may be in advance of
everything hitherto achieved, this sys-
tem of survey would not be recom-
mended. It is not impossible, however,
that, from this as a beginning, there
might grow, keeping pace with the gen-
eral progress of the country, a geodetic
institution that would be equal to the
1 best.
ORIGIN OF THIS SYSTEM.
The writer by no means pretends to be
the inventor of the combination of
methods described in these pages, al-
though hitherto there has been but little
description of them in print. An effi-
cient system of survey cannot be the in-
vention of any one man; it must be the
outgrowth of years of practical expe-
rience, resulting in the gradual accumu-
lation of ideas and improvements con-
tributed by those who have been en-
gaged upon it. This one is the result of
a growth of at least a quarter of a cen-
I tury, and therefore is not open to the
; serious objection of being new and un-
| tried. During that length of time, the
! enterprise of geographical surveying
[ has been receiving more and more en-
j couragement from the government of
| the United States, which has wisely
I adopted that plan, in connection with
1 geological and other scientific research,
as a means of opening and illustrating
' its vast public territory.
At the present day there are actively
| engaged upon this duty in that country
I three important commissions of survey.
| That of Dr. F. V. Hayden, geologist in
I charge, is known throughout the world
' bv its extensive and important work, not
180
van nostrand's engineering magazine.
only in geology and geography, but in
all their kindred sciences as well. A
second is under Major J. W. Powell, the
intelligent geologist and intrepid ex-
plorer who was the first to descend the
great canon of the Colorado River. An-
other, more strictly geographical in its
nature, is under the auspices of the War
Department, and is conducted by Lieut.
George M. Wheeler, an officer of envia-
ble reputation in the United States Corps
of Engineers. While the general plan
is much the same throughout these
three commissions, it is especially to his
former associates, the geographers and
officers of the last-named organization,
that the writer wishes to acknowledge
his indebtedness for whatsoever of value
there may be in this paper.
BRAZIL AND THE UNITED STATES.
Although, as has been stated hereto-
fore, it is not wise for any nation to copy,
blindly, and without adaptation to its
own peculiar needs, the system of sur-
vey employed by any other country, yet
it would seem that the processes that are
fitted to the United States would require
but little modification to be adapted to
use in Brazil, so analogous are the two
countries in many respects. They have
equal amounts of territory as near as
may be, but, peopling this territory,
there are four times as many inhabitants
in the United States as there are in
Brazil; thus it would seem that the me-
thods that are deemed sufficient for the
former would certainly suffice for the
latter. In each country the population
diminishes from a thickly-settled sea-
coast back into an uncivilized and almost
unknown interior. In each of these
there is a great amount of wild land
which the government is anxious to open
to colonization and cultivation. To ex-
pose and popularize the natural wealth
of this public domain, the U. S. Govern-
ment resorted to the plan of scientific
surveys, to which the Geological Com-
mission of Brazil is very similar in all
respects, and so efficiently have they
accomplished their purpose that it has
become a noticeable fact in the cartog-
raphy of the United States that its maps
of some of the remote and unsettled dis-
tricts of the Rocky Mountains are
superior to those of its oldest and richest
States, and, therefore, there are now
plans on foot looking to the extension of
these geographical surveys over the en-
tire surface of the country.
As the American manner of railway-
building, more expeditious and involving
less first cost than the European methods,
has been found practicable in Brazil, in
some instances, in which all other plans
would fail, so with this question of geo-
graphical surveys, it may prove to be the
American system or none.
RESULTS OF THIS SYSTEM.
Considering now the results that could
be expected from such a geographical
survey of Brazil, this question can be
best answered by referring to areas sur-
veyed in the same manner in the United
States. From Lieut. Wheeler's annual
report, which the writer has before him,
it appears that in six years' continuance
of his commission an approximate extent
of 800,000 square kilometers has been
surveyed. Allowing an average of five
parties in the field during that time, the
season's work of one engineer reduces
itself to about 25,000 square kilometers.
Allowing proportional returns from the
various other geographical surveys at
present in commission, or that have been
in existence during the last ten years in
the western portion of the United States,
it appears that one-third of the area of
that great country has been thus sur-
veyed in that period.
This is at a total expenditure which,
while including the cost of all other
concomitant scientific labors, to which
the geographical work has been in large
part incidental and tributary, has never
exceeded four hundred contos ($ 200,000)
per year. There is probably no other
department of public enterprise which
has yielded so extensive and valuable re-
turns for an equal amount of money.
AN ESTIMATE FOR ONE SEASON.
In general, an area of from 10,000 to
30,000 square kilometers, varying ac-
cording to the geographical nature of
the country, is assigned to each party
for a season of four, five, or six months,
and its ability to satisfactorily cover
that district in that time is conceded.
To illustrate the possibility of such rapid
progress, let us take a typical area of
20,000 square kilometers and see what
can be done with it by one party and
GEOGRAPHICAL SURVEYING.
181
one geographer in one season's work of
six months in duration. Of this time
the first month will be consumed in the
measurement and development of the
base, and in other preparation. Of the
remaining period one month more will
perhaps be lost in unavoidable delays
resulting from storms or other causes.
There will then remain four months,
which, at twenty-five available days in
each, will afford one hundred days for
active service in the field.
Allow one half of these days for the
meander survey, and the other half for
the occupation of mountain stations.
Fifty mountain stations will thus result,
and, in addition to these, there will be a
topographical station either upon or
adjacent to each day's meander. So
there are one hundred triangulation and
topographical stations distributed at
judicious intervals over this territory.
That is, there is one for every two
hundred square kilometers of ground, or,
typically, they are but about fourteen
kilometers apart, and the piece of coun-
try to be sketched in contours need not
extend more than seven kilometers in
each direction; this estimate ignores the
meander surveys, to which fifty days of
the season will be devoted, and by which
these stations will be separated and sur-
rounded.
At twenty-five kilometres a day, a very
reasonable allowance, the total distance
of meander route will be 1250 kilometres.
This distance would reach across our
area nine times, cutting it into strips of
sixteen kilometres in width. Hence, in
order to include the entire country from
this survey, the typical zone of each
meander would not reach more than
eight kilometres on either side of its
path ; but, since it would be superfluous
to sketch from this base the country in
the immediate vicinity of the mountain
stations, these plots en route need never
extend more than four kilometres from
the central line. Of course, in practice,
these surveys will not be thus distributed
in straight lines at equal distances apart,
but will communicate, intersect, and
duplicate in every possible way. Still
the meander will serve its original pur-
pose of penetrating those regions and
traversing those border-lands that are
remote from the mountain stations, and
will trace out the roads, trails, and im-
portant streams, whose entire length in
this area will not be likely to exceed
1250 kilometres.
Returning to the office at the end of the
season, the engineer will have material
enough to make a plot of the country on
a scale of one centimetre to the kilo-
metre (ioo1ooo)> or one-half a centimetre
to the kilometre (8oo1ooq)« ^r» t0 Put
this statement with more precision, he
will have so much and so detailed mate-
terial,that he will not be able to portray
it conveniently and intelligibly on a scale
of less than 1 0 £ 0 0 0 . But when the
final draughtsman comes to copy these
plots, he may condense them, if it be
thought expedient, to proportions of
4 0 o1 0 0 0 , or even smaller. On the oth er
hand, portions of this area may be plot-
ted upon a much larger plan than any
here noticed, should such be found nec-
essary for the clear and complete geo-
graphical and geological representation
of the same.
E UK OPE AN SURVEYS.
Now in contradistinction to the above
showing, let us take up the reports of
some European surveys. In Prussia,
12, ('00 square kilometers, a little more or
less, are surveyed annually, at a cost of
800,000 marks, or, as near as may be,
four hundred contos of Brazilian money,*
exclusive of the salaries of military as-
sistants; notice that in the United States,
with a total annual appropriation not
greater than this, at least 300,000 square
kilometers are geographically surveyed
each year, this territory being studied at
the same time by the geologist, the
chemist and the naturalist.
Upon the Ordnance Survey of Great
Britain there were over 1800 assistants
and employes engaged during the year
of 1874; the total area surveyed by them
was not more than 8,000 square kilome-
ters. With the methods in use in Austria
an experienced topographer can survey
in one field season of six months five
hundred square kilometers at the farthest.
In Switzerland the topography is in large
part done by contract, and it alone, ex-
clusive of triangulation and publication,
costs 700 or 800 francs per square stunde,
or about twenty-two mil reisf per square
* A conto of reis, in Brazil, is equal to about five hun-
dred American dollars, or a hundred pounds sterling.
t Eleven American dollars.
182
VAN NOSTEAND's ENGINEERING MAGAZINE.
kilometer. So with the surveys of Italy,
Spain, Sweden, and the other European
countries of comparatively small extent;
they are so slow, detailed, and withal so
expensive as to be inapplicable to the
great empire of Brazil.
AN ADVANTAGEOUS DEVELOPMENT.
So vast is the extent of this empire
that the idea of a geographical survey
of its territory, as a whole, is an astound-
ing one, and is liable, in itself, to forbid
all further consideration of the subject.
But this plan does not necessarily imply
the regular extension of this survey over
the whole country, irrespective of popu-
lation and wealth. On the contrary it
would devote itself at first to such areas
as, from geological or other economical
reasons, might most urgently require it,
and a region of especial interest to the
geologist would be surveyed first and
with especial care, to the neglect or even
exclusion of those great stretches of
country whose structure is unvaried and
monotonous. In a few conditions of its
plan, as, for instance, in the system
adopted in the projection of its maps, it
might provide for any possible ultimate
extension, but in other respects it could
operate with equal facility, in whatever
districts might be assigned to it.
Nor does this plan imply the necessity
of any great outlay at the beginning, but
would ask to start upon a small scale at
first, with a view to gradual growth as it
proved itself worthy of encouragement.
As the aim of this project would be not
only the production of much-needed
maps, but also the introduction of these
methods of survey from abroad, and the
training of Brazilian engineers in the use
of the same, any very extensive initial
basis would prove not only embarrassing
at first but also probably disastrous in
the end. A survey inaugurated upon a
grandiose scale is too liable to exhaust
the patience and liberality of its official
patrons before it can exhibit results ap-
parently equivalent to the expenditure
that it has caused, and the frequent fate
of such enterprises is that they are dis-
continued at about the time when, then-
organization being successfully com-
pleted, they are prepared to enter upon
an area of efficient and fruitful labor;
hence, all of the expense of organization
and other preliminaries becomes a total
loss to the government.
On the other hand, some of the most
important surveys of the world have
arisen from humble beginnings. Such an
enterprise educates its own members, the
assistant engineer of one season becom-
ing the engineer of the next, and so on.
It develops gradually and with a healthy
growth, perfecting its own methods, and
always experimenting upon a small scale,
so that it is never liable to serious disas-
ter. And, above all, by its early pro-
duction and exhibition of results com-
mensurate with its size, and with its
cost, which is insignificant at first, it
buys the right to be continued, en-
couraged and increased from year to
year.
A GEOLOGICAL AND GEOGRAPHICAL SUR-
VEY.
There are two very good arguments
for such a geographical survey in connec-
tion with the Geological Commission of
Brazil; first, its necessity to the geologi-
cal survey, as explained in the early part
of this paper; and second, because in
such a connection it can work most
economically and profitably. With a
combination of these elements comes
much valuable co-operation between the
representatives of the various branches
of science, and this is constantly acting
to lessen the expense and increase the re-
turns of such a survey. For instance, as
the meteorologist of the engineering
corps, an assistant with some acquaint-
ance with geology, could be chosen. As
his meteorological duties upon the march
would be but light, he could devote
much of his time to a geological study
of the road, leaving the regular geologist
at liberty to go from camp to camp by
any other route that he might select.
Again, the meteorologist, or even the en-
gineer himself, may make stratigraphical
sketches upon every mountain, and bring
specimens of rock from the same, while
the geologist is away upon some detour
to regions of interest in another direc-
tion.
Or, reversing this illustration, the
geologist, whose profession is so closely
allied to that of the geographer, is con-
stantly making notes of direction,, dis-
tance, slope, and altitude, which are of
the highest importance and use in the
WOKK OF EXGLNEEKS IN KEFEKENCE TO PUBLIC HEALTH.
183
construction of a map. These are lost
to the world if there is not an accom-
panying geographical survey into whose
plots they may be assimilated.
In witness of the sympathy with
which the present members of the Geo-
logical Commission regard geographical
work, and of their skill in the prosecu-
tion of the same, the writer would men-
tion their intelligent and extensive sur-
veys of the valley of the Amazon, from
Monte Alegre westwards, and of its
tributary, the Trombetas; of the island
of Fernando de Noronha; and of many
localities along the Atlantic coast and
elsewhere in the empire. These are evi-
dences of a willingness and an ability to
collect geographical information, which,
in themselves, assure the success of a
system of geographical surveying in
connection with the Geological Commis-
sion of Brazil.
ON THE PRESENT AND FUTURE WORK OF ENGINEERS IN
REFERENCE TO PUBLIC HEALTH.*
By Mr. W. DONALDSON, M. A.
From " The Builder."
Inteemittent downward filtration by
irrigation over wide areas affords the
only means of readily overcoming all the
difficulties of sewage purification. Puri-
fication by continuous drenching of the
land, generally called intermittent down-
ward filtration, cannot be successfully
carried out without the use of settling-
tanks; that is, not without the necessity
of piling up heaps of sewage sludge
which has very little manurial value.
The getting rid of this sludge must,
therefore, entail a yearly loss. It is true
that on many, probably on the majority
of irrigation farms where utilization and
purification are combined, these tanks
are used for the clarification of the sew-
age before it is turned on to the land,
but there is, however, not the least neces-
sity for their use. If the sewage is kept
in motion, the fine sediment is deposited
evenly over the surface of the land
during the process of flowing, and does
not leave any visible indications of its
presence, if there is an adequate area of
land under irrigation. It is, of course,
necessary to separate all solid bodies
from the sewage by means of screens,
but the total of these screenings is very
small. At Reading, including the de-
posit of heavy sand in the screening
tanks, the average daily quantity does not
exceed three-quarters of a cubic foot per
thousand, but at Reading the duplicate
system is strictly carried out, and the
* Abstract of an Address before the Sanitary Institute.
sanitary authority has not to deal with
the road grit nuisance.
Colonel Jones has adopted these set-
tling-tanks on the Havod-y-Wern Farm,
and is now engaged experimenting on
the sewage sludge with the hopes of
making it salable at a profit. He may
possibly find a profitable market for the
small quantity deposited in the tanks at
Wrexham, but his success will only be
partial. Until manure made from sludge
can be sold at a price which will admit
of carriage to a long distance, the use of
settling-tanks must entail a yearly loss.
In my opinion, the want of success on
irrigation farms has been in no incon-
siderable degree owing to the half-heart-
ed way in which the advocates of utiliza-
tion have taken up the question. They
ought to have regarded purification as
quite a secondary consideration, because
utilization must necessarily accomplish
successful purification. The problem
which they have hitherto attempted to
solve has still been, how few acres will
effectually purify the sewage of 1,000
people ? The exact converse ought to
have engaged the whole of their atten-
tion, how many acres will the sewage of
1,000 people effectually fertilize. The
nuisances occasionally experienced on
sewage farms, which are the main cause
of the difficulty of acquiring land, need
never occur except in those cases in
which the minimum standard of acreage
requisite for purification has been
adopted.
184
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Sir Joseph Bazalgette at the discussion
by the Sanitary Institute in March, 1SV7,
upon the mode of treating town sewage,
arguing from the example of London,
came to the conclusion that it would not
be possible to obtain land in the neigh-
borhood of large towns in sufficient
quantity and suitable quality and free
from residences, for the purpose of sew-
age farming. He comes to this conclu-
sion because London with a population
of 4,000,000 would require an area of
sixty square miles, which, expressed in
another way, is an area less than eight
miles square. London is, however, about
ten times larger than any other town in
the kingdom, so that arguments against
the adoption of irrigation derived from
the example of London, even if well
founded, are not applicable to any other
case. In my opinion, however, the argu-
ment is not in any other respect well
founded. Surely in a food-importing
country like England, the more acres the
sewage manure will not only fertilize,
but render at least doubly more pro-
ductive than they can be made by any
other manure, the better for the people.
It is not necessary that the area required
for irrigation should be either in the im-
mediate neighborhood of the town from
which the sewage has been sent, or free
from residences. If a sufficient area is
used, no nuisance will be occasioned, and
sentimental fears on that head can easily
be allayed by interposing a belt of un-
irrigated land.
If the Town Council of Manchester
can bring water from Thirlmere to Lan-
cashire and sell it at a profit, it is clear
that sewage may be conveyed to an
equal distance and also sold at a profit,
if its commercial value is equal to that
of the water. For the purpose of com-
paring the values of the two commodi-
ties we must not adopt as the standard
of the value of the water the price at
which it is sold, after having been dis-
tributed throughout the district to each
set of premises, but what it is worth in
the service reservoirs. In order to as-
certain its value in the service reservoirs
we must deduct the cost of distribution,
which includes nearly all the cost of
management and maintenance, not from
the price at which it is sold for house-
hold purposes, but from that at which it
is sold in large quantities for commercial
purposes, because Waterworks Com-
panies do not sell any water at a loss.
Taking all these points into considera-
tion we cannot assign a higher value
than 2d. per thousand gallons to the
water in the service reservoirs previously
to distribution.
In the Reports of the Rivers Pollution
Commissioners the manurial value of
sewage is said to vary from a maximum
of 2d. per ton in dry weather to a mini-
mum of -|d. when the sewage is diluted
with storm water. According to these
estimates the value of crude sewage
varies from 2jd. to 9d. per thousand
gallons.
I am well aware that you will not re-
gard the theoretical estimates of analy-
tical chemists as evidence of much value
in support of my views as to the actual
value of dry weather sewage, because it
is the general opinion that this value can
never be realized. I shall therefore en-
deavor to show you that this view of the
question is erroneous, that in reality the
smallest value is in all cases actually
realized by the production of magnificent
crops, and that the failure takes place in
the next stage. The full value of the
crops is not realized. Irrigation farms
in the hands of practical farmers, who
understand the art of making the most
of the farm produce, cannot fail to pay
handsome returns in hard cash, but prac-
tical farmers keep their balance-sheets to
themselves.
On the basis that the sewage of 100
people can properly fertilize only one
acre, and at the rate of twenty gallons
per head of sewage, which is a high esti-
mate where the separate system is in
force, one acre will acquire annually
730,000 gallons. We have now to con-
sider what that acre of land under sew-
age irrigation is capable of producing.
One acre sown with rye grass will pro-
duce five or six crops a year, — fully sixty
tons of grass. This is sold at prices
varying from 10s. to 20s. according to
the demand and the locality of the farm.
Estimated at only 10s. per ton the gross
return would be about £30 per acre.
From corn and root crops the gross re-
turn is worth from £20 to £30 per acre.
Against this amount is to be debited
rent, taxes, working expenses, and in-
terest on farm capital. If the land is
let at an ordinary agricultural rent, £12
EEPORTS OF ENGINEERING SOCIETIES.
185
a year ought to cover all the yearly
charges under these heads, and a balance
of from £12 to £14 per acre would be
left to divide into tenant's profits and
payment for the sewage as & manure.
If this be divided equally between them
the amount paid for the sewage would
be over 2d. per thousand gallons. If £3
a year per acre in addition to interest on
sunk capital be considered a fair tenant's
profit, the value of the sewage would on
that basis be more than 3d. per thousand
gallons.
In Colonel Jones's pamphlet on the
Havod-y-Wern Farm it is stated that the
average net profit for five successive
years amounted to £3 4s. 4d. per acre.
The rent paid by Colonel Jones is near-
ly £5 per acre, so that the rates and
taxes must be proportionately heavy. As
he is only tenant, he puts on the debit
side a yearly sinking-fund, to recoup
himself for capital sunk in permanent
improvements, which amounts to about
Vs. per acre; with this addition the total
net profit made by Colonel Jones is about
£3 lis. per acre. This, however, rep-
resents only part of the whole profit.
The cows fed on the farm are owned and
kept by another man, who is presumed
to live on his profits, but publishes no
accounts. There are only ninety-two
acres, so that the profit made by the
cow-keeper cannot well be less than 30s.
an acre. If the rent paid by Colonel
Jones had been an ordinary agricultural
rent, his profits would have been in-
creased by a deduction of fully £3 10s.
from the debit side in the amount
charged for rents, rates and taxes. Mak-
ing these allowances, the total net profit
made on the Havod-y-Wern Farm has
been, on an average of five years, fully
£8 per acre.
The successful disposal of sewage crops
is at the very root of the whole matter.
To state that there is a difficulty in find-
ing a market for them in some cases is
tantamount to saying that there is no
home demand for milk, butter, cheese
and beef. The produce must be con-
sumed on the farm and converted into
food for man before it is brought into
the market. This work can only be suc-
cessfully carried out by private enter-
prize. So far, therefore, as the interest
of Sanitary Authorities are concerned,
the only point to be considered is the
question of the rent at which they will
be able to let irrigated land.
REPORTS OF ENGINEERING SOCIETIES,
American Society of Civil Engineers.—
The annual convention of this society was
held at Boston, beginning the 18th of June and
adjourning on the 22d. The discussions and
the excursions to neighboring localities were
carried out in accordance with the programme.
The last number of the "Transactions"
contains the following papers :
156. On a new method of detecting over-
strain in Iron and other metals, and, on its
application in the investigation of the causes
of accidents to bridges and other constructions.
Bv Prof. R. H. Thurston.
"157. Steam Engine Economy. A uniform
basis for comparison. By Chas. E. Emery.
158. The Inclined Plane Railroad at Madi-
son, Ind. Its history and operation. By M.
J. Becker.
S
IRON AND STEEL NOTES-
el v. Iron.— There is nothing in which
modern progress is better exemplified than
! in the manufacture of steel for all purposes for
I which iron was formerly used. Thanks to the
i inventions of Bessemer and Siemens, we have
arrived at the stage, where best quality steel
rails, in some cases guaranteed to remain sound
during a wear of ten years, are sold at prices
j very little higher than ordinary iron rails. A
similar result is likely to follow with respect
i to the plates used for boilers and shipbuilding.
Steel is now produced by the Bessemer and
the Siemens-Martin processes, which with a
tensile strength one fourth greater than iron,
gives such superiority in elongation, reduction
of area at point of fracture, bending, flanging
and twisting, as have not been even approxi-
mately approached by the very best Yorkshire
iron at considerably higher prices. We have
seen specimens, showing results which might
have been expected of copper, but not of iron
or steel. " We are surprised at hearing that the
world-renowned best Yorkshire iron seems
destined to be superseded by this mild steel in
the same way as steel rails have taken the
place of the iron ones.
We have obtained from Messrs. John Brown
and Company (Limited), some interesting in-
formation on the subject of the manufacture
and the capabilities of this material manufac-
tured at their works by the Bessemer process,
and the systematic care taken in the different
stages. Each heat is tested chemically and
mechanically, and each plate is also tested be-
fore being sent out, thus insuring that unifor-
mity which is so much to be desired, and pre-
venting the possibility of any unsuitable mate-
rial being supplied. For this class of steel
only the best and purest pig-irons are used in
the proportions which long experience and the
continually repeated analyses show to be most
suitable. As soon as the operation of conver-
sion is completed, and the preliminary bend-
ing-test and the analysis of the steel show that
186
VAN NO strand's engineering magazine.
it is of the desired "dead-soft" temper, an in-
got is hammered and rolled into plates, which
are annealed and then subjected to tensile,
bending and welding tests. For the tensile
test, strips planed out of the plates are placed
in a lever-testing machine specially con
structed for this purpose, and the load is in-
creased until the pieces are torn asunder. The
strain at the point of fracture should be be-
tween twenty-six and thirty tons per square
inch. If found higher than this last-named
strain, the heat is not used for boiler plates. In
steel within the above limits of tensile strength,
the test piece, eight inches long, will be found
to have stretched at least twenty per cent, be-
fore breaking, and its sectional area at the
point of fracture reduced about fifty per cent. ;
showing very great ductility as well as great
strength. For the bending test similar strips
are heated to a cherry-red heat, and quenched
in cold water until quite cold, and then bent
over close. This they must do without signs
of fracture. Other strips are heated to a weld-
ing heat and lap-welded in the same way as
iron is welded, the square ends of the strips
not being in any way prepared for welding.
On the sample ingot satisfying all these tests,
the whole heat, varying from eight to ten tons,
is used for boiler plates, which may be re-
quired to weld. If only the two first tests are
satisfied — which is sometimes the case — the
steel is used for ship-plates or shell plates of
boilers, where it is not required to weld.
When the plates have been sheared to the size
ordered, they are annealed, that is to say, put
into a heating furnace heated slowly and uni-
formly and allowed to cool slowly. A strip
cut off every plate is subjected to the quench-
ing test above described, and being stamped
with the corresponding consecutive number of
the plate, a record is kept of its quality before
being sent out. Should any one of the tests
not be fully up to the standard, the plates to
which they belong are rejected. Thus the
quality of each plate sent out is known and
approved, and the fact of the plates being sent
is an assurance to the consumer that the quality
has been fully ascertained to be suitable for
the purpose required. We understand there
has been a prejudice against steel for boilers,
owing to the want of uniformity which ex-
isted in years gone by, but this uniformity is
now completely obtained. In answer to our
inquiries if any difference of treatment is
necessary in the use of this steel in place of
iron, we are informed that, like all steel, it
should not be heated as much as iron for flang-
ing and welding, and that after recent careful
experiments, Lloyd's surveyors have arrived
at the conclusion that plates up to ^-inch
thickness inclusive may be punched without
more damage to the material than is caused by
punching iron plates, but that plates above \
inch thick should be drilled, or, if punched,
afterwards rimed at least ^-iuch, or annealed.
Either of these operations w ill leave the mate-
rial at the original strength per square inch of
sectional area, and it is therefore recommended
to treat all plates below ^-inch thick when
possible, as well as thicker plates, in one of
the three ways described. It is also recom-
mended that all plates which have been flanged
should be annealed to restore the material to a
state of rest, as the annealing will effectually
remove the various and considerable strains
set up by the present method of flanging the
plates — by heating the plates locally first in
one place and then another for flanging.
Among the samples illustrating the preced-
ing remarks, shown us by John Brown and Co. ,
are some very extraordinary ones. One is a
finch steel plate dished cold, the inside dia-
meter being 10 inches, and depth, 5f inches.
A similar plate was bent five times upon itself
without a crack. Another plate was punched
with sixty-one holes of £ inches diameter, with
only ^-inch spaces, showing very little distress
to the metal. Ordinary twists and bends are
hardly worth quoting, but a ^-inch square bar
subjected to six complete twists without a
crack is so exceptional a test that it must be
mentioned. These, however, are tours deforce.
A practical fact in the same direction is that
steel angles, 9 inches by 4 inches by -J inch,
are rolled in forty feet lengths for Midland
Railway coaches, and that beater-bars for
thrashing machines are rolled in great numbers
for Messrs. Garrett, and other eminent makers,
and every satisfaction is given by the material.
— Iron.
RAILWAY NOTES.
VI ew Transportation Car. — The Ashbury
\S Railway Carriage and Iron Company,
Openshaw, have constructed a novel kind of
railway wagon, specially adapted for convey-
ing dead meat, fish, fruit, or other perishable
goods. The vehicle, which externa] ly resem-
bles an ordinary wagon, is built with double
walls, and the intervening space is filled with
layers of non-conducting substances — namely,
sawdust and paper. The whole of the interior
is lined with galvanized zinc, which also com-
poses the bars and hooks upon which the meat,
&c, would be hung. Along the roof runs a
semicircular chamber capable of holding
twelve cwt. or fourteen cwt. of ice, and into
this chamber the air is first introduced, after
the freight has been deposited in the van and
the door hermetically sealed. After passing
through the ice, the air is forced through a
receptacle filled with charcoal, which dries it,
and then circulates among the contents of the
wagon. It is afterwards discharged through
an automatic discharge pipe. This is the first
wagon of the kind built for any English rail-
way, and it is intended for service between
Scotland and London. With this contrivance
meat can be kept perfectly fresh for rive or six
days, and in case of the market being over-
stocked the meat may be kept in the van,
which is thus converted into a temporary
storehouse. The arrangements for cooling
and drying the air have been designed by
Colonel W. D. Mann, of the United States
army, who has had considerable experience
upon the railways of America and the Conti-
nent.
C cheapest Railway in the World. — The
; cheapest railway in the world is to be
KAIL WAY NOTES.
187
found in the peninsula of East Frisia, in the
extreme north-west of Germany. The penin-
sula has the thinnest population anywhere to
be found in central Europe, and the soil is
almost completely moor. A railway was,
some years ago, built with Government assist-
ance, connecting Bremen and Oldenburg with
the town of EmdeD; but this line had to be
laid down absolutely straight, to save expenses.
This left the village of Westerstead five miles
from its track, to the distress of the inhabitants,
who tried to persuade the Government to
deviate from the straight line. When they
found that all petitioning was useless, they
determined to make a railway of their own.
It appeared almost impossible to construct a
line that would pay its expenses, among a
population of ten inhabitants per square mile,
wholly agricultural, exporting nothing but
cattle, pigs, and the scanty produce of the soil,
and importing Utile else but a few articles re-
quired for domestic consumption. But the
parish of Westerstede may now, says the Rail-
way News, boast, probably beyond challenge,
of possessing and maintaining the cheapest
railway in tne world. The line, which is a
single one throughout, is about five miles long,
running from the hamlet of OcholL, and to the
village of Westerstede, the terminus here being
the yard of the principal inn. It has a gauge
of 2 feet 5-£ inches, and the rails, made of Besse-
mer steel, and weighing twenty-five pounds to
the yard, are of the Vignoles shape, connected
by fish-plates only, so that they rest directly on
the sleepers. Although the country is per-
fectly level, consisting principally of moorland
and heath, the earthworKs were not altogether
unimportant, as considerable drainage worts
had to be carried out to protect the railway
from occasional floods, to which the wThole of
East Friesland is liable, since it rises but little
above the level of the North Sea. Tne line
has its own earthworks, but runs for some
distance close alongside the ordinary road,
separated from it by a ditch and a quickset
hedge. There is but one station on tne line,
half-way between Ocholt and Westerstede;
but, strictly speaking, this is no station at all,
but merely a halting place for the trains. A
forester's cottage stands here, the owner of
which allows intending passengers to sit down
in his room and await the arrival of the trains.
The rolling-stock consists of two small tender-
locomotives, three passenger carriages., two
closed goods vans, and four open trucks. The
locomotives, four-wheeled, with a wheel base
of 5 feet, and a heating surface of 172 square
feet, weigh seven and a-nalf tons when loaded
with fuel and water; they only bum peat,
abundant in the district, and have, instead of a
whistle, a bell, which is rung at every level
crossing. The passenger carriages each hold
twenty-eight passengers, sitting omnibus fash-
ion, with a door at each end, which arrange-
ment is necessary as the trains cannot turn,
there being no turntable on the line. The
working staff consists of four persons, an en-
gine driver, a fireman, a guard, and a plate-
layer, their total wages not amounting to more
than 13s. a-day. The entire working expenses
are returned as exactly £ 1 9s. pei diem, the
items of expenditure being, besides wages, 6s.
for peat-fuel, and 10s. for maintenance of per-
manent way, repairs, grease, and other indis-
pensable matters. There are no buildings on
the line, except a rough shed for the cover of
engines and carriages at each end; nor are
there any signals. The passenger fares, which
are low, being 6d. first-class 4d. second-class,
are collected by the guard. He also accom-
panies the goods trains, collecting the charges,
which are Is. for a beast, 3d. for sheep and
pigs, and at the rate of 2s. per ton for general
goods. Pigs are the chief article of export of
the district. The company, composed entirely
of inhabitants of the disirict, including agri-
cultural laborers, raised a total capital of
£11,200, and of this only £10,450 were dis-
bursed in the building of the line, purchase of
rolling-stock, and erection of sheds, leaving a
surplus of £ 750, which sum was placed aside
as a reserve fund. To aid in starting the
undertaking, the parish of Westerstede, by
vote of the communal representatives, sub-
scribed £ 1500 as a gift, to be returned only in
case of the repayment of the whole of the
debenture capital. From the returns as yet
published, it appears that, in the first seven
months during which the line was open for
traffic, the gross receipts came to an average of
£2 8s. per diem, so that, with working ex-
penses of £ 1 9s. , the net earnings were at the
rate of 19s. a-day.
ENGINEERING STRUCTURES.
A Great Engineering Feat.— The new rail-
way bridge over the liver Tay was opened
with much ceremony on the 31st May. The
first movement to bridge the Tay was made
about forty years ago by the Edinburgh and
Northern (afterwards the Edinburgh, Perth <fc
Dundee) Company. It was not till 1871, how-
ever, that a project destined to be fulfilled was
initiated. In 1S70 the necessary Act of Parlia-
ment was obtained, and on the 8th of May of
the following year the contract for the erection
was signed. The contract was transferred in
1873 to Messrs. Hopkins, Gilkes & Co., of
Middlesborough; and Mr. A. Grothe, who was
engineer and manager to Mr. De Bergue, and
had shown very great professional skill in the
manner in which he proceeded to erect so
i gigantic a structure was continued by the new
: contractors, and the admirable, thoroughly
j substantial bridge which now spans the river
J is a proof of their wisdom in taking Mr.
Grothe into their service. The bridge is 10,612
| feet in length— or two miles and fifty-two feet
I —and is thus the longest railway bridge over a
| running stream in the world. The Victoria
'■ bridge, Montreal, comes next in respect to
! length, being 9194 feet, or 1418 feet shorter
j than the 1 ay bridge. A still more extraordi-
nary bridge than either is one on the Mobile
J and Montgomery Railroad, Called the Texas
and Mobile bridge, which is fifteen miles m
length; but as the greater part of it is carried
^ver immense morasses, it cannot be fairly
compared with the Tay bridge, which spans a
i tida^ river. The bridge starts from the Fife
188
VAN nostrand's engineering magazine.
side of the Tay, where the land is about
seventy feet above high water, and gradually
rises at a gradient of 1 in 356 until the highest
part of the bridge is reached, being 13(f feet
from the level of the rails to high- water mark.
The greatest altitude occurs at the center of
the large spans, and from this point towards
the north side there is a sharply falling gradi-
ent of 1 in 74. In the structure there are
eight3'-flve spans of the following dimensions :
eleven spans of 245 feet each, two spans of
227 feet each, one span of 166 feet, one span
of 162 feet 10 inches, thirteen spans of 145 feet
each, ten spans of 120 feet 3 inches each,
eleven spans of 129 feet each, two spans of 87
feet each, twenty-four spans of 67 feet 6
inches each, three spans of 67 feet each, one
span of 66 feet 8 inches, six spans of 28 feet 11
inches each. All the spans, with the exception
of that of 166 feet, which is made by a bow-
string girder, are formed of lattice girders, but
in addition to these spans, there are adjoining
the north end of the bridge : one span of 100
feet, bowstring girders; one span of 29 feet,
plate girders. The thirteen largest girders,
each being about 200 tons in weight, are in the
center of the bridge, and over the navigable
part of the river. The girders are arranged in
continuous groups, with proper provision for
expansion, and are all supported on piers of
varied construction. The permanent way con-
sists of double-headed steel rails, fished at
the joints in twenty-four feet-lengths, weigh-
ing seventy five lbs. to the yard, and secured
by oak keys in cast-iron chains. The chains
are fixed at intervals of about three feet to
longitudinal timbers seventeen inches wide,
and varying in depth from seven to fourteen
inches. Throughout the whole length of the
bridge each rail is provided with a guard-rail
to afford additional security to trains passing
over the structure. The rioor of the bridge
consists of 3-inch planking, and is covered with
a waterproof composition. On both sides of
the bridge, for its whole length, a strong hand-
rail is erected, and painted in a light blue
color. The foundations of the piers are
formed of iron cylinders, with brickwork and
cement. Fourteen piers at the south side are
built entirely of brick, and on rock foundation,
and consist of two cylinders of nine feet six
inches in diameter, connected by a wall of
brickwork three feet in width. At the four-
teenth pier it was found that the rock suddenly
shelved away to a great depth, under beds of
clay, gravel, and sand, and therefore another
kind of pier had to be resorted to which would
give an equally sure footing. The weight of
the pier was lighted by substituting for the
heavy brickwork above high water cast-iron
columns, fixed together by horizontal and dia-
gonal transverse bracing, and the cylinders
were increased to fifteen feet in diameter. The
whole of the piers after the fourteenth are
built in this manner, but in the case of the
highest pairs, supporting the 245 feet spans,
they have a cylindrical base of iron and brick
in cement thirty-one feet in diameter, and from
forty to forty-five feet in depth, standing a few*
feet above high water. The whole of the
cylinders supporting iron columns are finished
with a coping of Carmyllie stone. The first
stone was laid on the Fifeshire side on the 22nd
July, 1871, and on September 25th, 1877, six
years afterwards, the directors and engineers
had the satisfaction of crossing over the
bridge for the first time in a train. The con-
tract price of the bridge was £ 217,000, but the
actual cost is £350,000, the great increase
being caused because of the original plans
of the piers having to be departed from, and
plans prepared of another description of piers
adapted to the soil in the bottom of the river.
The quantities of materials used in the structure
are as follows: — 3520 tons of cast iron, 6281
tons of malleable iron, 90,600 cubic feet of
timber, 8600 of cement, 4,350,000 bricks,
27,000 cubic feet of dressed ashlar, and 355
cubic yards of rough ashlar. The engineers
engaged in the construction of the bridge
were: Messrs. Alfred Grothe (superintending
engineer) Frederick W. Reeves, G. G. Law-
rence, R. S. Jones, Theodore D. Delprat, G.
D. Delprat, and Thomas Templeton. On Mr.
Grothe devolved the responsibility of carrying
out the works, and he has done so with re-
markable success.
ORDNANCE AND NAVAL.
Monster Ordnance. — It has been known
for a fortnight past that the Government
was in treaty with Sir William Armstrong for
the purchase of four 100-ton guns which are
near completion at Elswick, but it was con-
sidered prudent to keep the negotiation secret,
as there were other bidders for the monster
weapons in the European market. Arrange-
ments are now completed by which these four
guns have become the property of the British
nation, and in the course of two or three
months they will be ready for mounting on
board any ship that is prepared to carry them.
It is not likely, however, that they will be
placed on shipboard for some time to come, for
the Admiralty have made no provision for
them, neither does it appear that the present
condition of naval armaments shows any de
mand for such miglny ordnance. The chief
argument for their acquirement was the appre-
hension that they might become^ the property
of another Power, and so enable it to dominate
the sea. At present, although Italy has 100-
ton guns for the two latest war ships, and
England has ready her 80-ton guns for her
Majesty's ship Inflexible, there is no armor
afloat which can resist the 35-ton and 38-ton
" Woolwich Infants," which have during the
last few years been produced at the Royal gun-
factories in the Royal Arsenal, Woolwich, and
employed in the national defences by land and
sea. The subject has fully engaged the atten-
tion of the Government, and the desirability of
manufacturing something heavier than the 80-
ton gun has been strongly advocated, but while
foreign nations plate their ships with anything
less than 19| inches of iron they are regarded
as at the mercy of the 800 lbs. Palliser projec-
tile fired by the 38 ton gun, and the authorities
have consequently hesitated about taking a
step still further in advance. The reflection,
ORDNANCE AND NAVAL.
189
however, that the Inflexible, with its 24 inches
of armor-plating, would be defenceless against
the 100 ton guns which Italy possesses, and
some other Power might have possessed, has
now induced the Government to conclude the
present purchase, and, furthermore, to consider
whether they should stop at this point. It is
pretty well authenticated that the Italians have
provided themselves with a steel-plated target
which even their 100-ton gun cannot penetrate,
and that they are preparing a ship which shall
be defended with this armor. In view of this
circumstance, the authorities were recently
deliberating upon the production of a much
more powerful piece of ordnance, and it was
anticipated that an order would be given before
long to the Royal Gun Factories for a gun of
over 200 tons. The drawings for such a
weapon were prepared long since, the^ ma-
chinery is all prepared for constructing it, and
all that is required is the order to proceed.
Such a gun would throw a shot of some three
tons weight, and pierce three feet of solid
armor. It m ould, however, take two years to
make, and perhaps another year for experi-
ments; but the manufacture of a ship which
would have a chance even with the guns of the
present day would take at least as long. It is
now, however, determined that a 200-ton gun
shall not be made at Woolwich. — Engineer.
ANew Piece of Heavy Ordnance. — The
Washington Herald says: — The Ordnance
Department of the Army has constructed a
large rifled gun, weighing about 90,000 lbs.,
with a calibre of 12.25 inches, which is now
undergoing proof at the Sandy Hook proving
ground, under the direction and supervision of
the Ordnance Board. So far the limited firings
have developed the most satisfactory results.
The gun is of cast iron, lined with a coiled
wrought-iron tube, with a length of bore of 227
inches, and is mounted on a carriage of late
design, with all the modern improvements to
control recoil and to facilitate loading and
maneuvering. Although as yet the firings have
been limited, still enough is known of the
power of the gun to say that for use against
ironclads it is equal, if not superior, to any gun
of the same calibre in any service. The essen-
tial features which contribute to any superiori-
ty over others in this respect are length of bore,
character of projectile and powder. In the
foreign services the English 12-inch wrought
iron gun has a length of bore of 198 inches; the
Krupp calibre 1-4.008, has 222.5 inches; the
Italian 12.6 has 252 inches; while the American
is 227 inches long. This length adopted .by
the Ordnance Department gives all the usual
effects that can be obtained from this source,
and secures a thorough consumption of the
maximum powder-charges, as has been practi-
cally proved by the absence of any uncon-
sumed grains of powder after the discharge.
The powders used have given marked supe-
riority in velocities and pressures over those
used in foreign services, the velocities being
greater for corresponding pressures, and the
pressures much less for the service charges.
No undue pressures have shown so far from
the use of the adopted system of projectiles,
no erosion or guttering are apparent, and per-
fect rotation has resulted from the rifling and
sabot employed; and this, with the absence of
any stripping, has given that accuracy of flight
so necessaryfor a successful rifled projectile.
The energies attained, or rather the capacities
for work — the gist of the whole subject — com-
pare most favorably with those of foreign'guns,
although the difference in charges and weights
of projectiles do not, so far, admit of a com-
plete comparison; but enough is known to
show that this gun has an equal, if not a
greater, capacity for work of any of the foreign
service rifles of like size. For instance, the
English 25-ton gun has given less energy by,
say, 450 foot tons, with 85 lbs. of powder and
a 600 lb. projectile, than the American; and
the Krupp, with 88 lbs. of powder and 664 lbs.
of projectile, 1254 foot-tons less; while the
Italian, with 100 lbs. of powder and 770 lbs. of
projectile, has only yielded a little over 400
foot-tons more; and in these comparisons the
American gun only uses 80 lbs. of powder
with a 600 lb. shot. But with 110 lbs. of
powder and 700 lbs. of projectile the American
rifle gives 9551 foot-tons muzzle energy, or 246
foot-tons per inch of shots circumference, an
energy about as great as any gun known for
this charge, and decidedly superior to Krupp's
and the Italian, using heavier charges. With
these encouraging results, by developing a
strong and durable system of gun construction,
with our superior powder and projectiles, and
with our rifling and length of bore, it would
seem that the Ordnance Department has pro-
duced a weapon able to cope successful!}' Avith
the best foreign guns, and at a much less cost.
The Electric Fuse and Heavy Cannon. —
It seems as if we were about to abandon
the old method of firing guns on board ship
with the lanyard, and to use the electric fuse
instead, at any rate, so far as heavy cannon are
concerned. For some years past experiments
have been carried on in the navy with electric
firing, but it is only since we have had to do
with very heavy guns, and particularly those
in turrets, that this method of discharge has
become almost indispensable. To be cooped
inside a close iron turret in company with a
pair of terrible weapons of 35 or 38 tons, and
to experience the full measure of their thun-
der, is scarcely to be contemplated with indif-
ference ; yet this is not the reason, or at least
not the principal reason, why the electric cur-
rent is to be employed in future instead of the
gunner's arm. The real cause is twofold; in
the first place it is possible to take better aim
\>y using electricity to do the work; and, sec-
ondly, the effect of the shots is more terrible.
The simultaneous discharge of three or four
projectiles against heavy armour has been
found capable of penetrating the latter, when
single shots are quite unable to do so. A
vibration is set up in the iron plating, it is pre-
sumed, and in this condition the armor is more
vulnerable. Simultaneous firing is impossible
by hand and word of command, in the same
way as gunners used to fire broadsides in the
old three-decker days. To the ear the thunder
of discharge might not appear otherwise in-
190
VAN nostrand's engineering magazine.
stantaneous, but the effect upon an ironclad is
vastly different if a volley is fired by lanyards,
or by a flash of electricity. The other reason
is more important still. The guns are so close
to the water, and the portholes so limited in
size, that sighting along the weapons is fre-
quently a matter of difficulty. The operation
is much more easily performed by an officer
stationed above, either in the rigging, or in the
armored tower, with which most of our mod-
ern ironclads are fitted. Provided with suita-
ble sights and electric wires which lead down
into the batteries, the captain, or other officer
of the ship, here has the whole of its armament
under his hand. He directs at what angle the
guns shall be laid, and, watching his oppor-
tunity, discharges them simultaneously at the
instant he thinks most fit. Situated above the
deck he is removed from the bustle and smoke
below, and can act with more coolness and
judgment, while obviousty no time is lost when
the critical moment for firing arrives. —
Standard.
The 6-inch Armstrong Breechloader. —
The experiments with a 6-inch breech-
loader, submitted to the test by Sir William
Armstrong, have been completed at Shoebury-
ness, to which place the gun was removed at
the close of the preliminary experiments at the
proof butts adjoining the Royal Arsenal, Wool-
wich, and the gun has been handed over to the
maker. It has made some excellent practice,
and the velocities recorded have been very
high, heavy charges of pebble powder having
been employed, with projectiles of from 60 lbs.
to 70 lbs. in weight. The breech arrangement,
which is on the French screw system, has been
greatly improved by the introduction of the
Elswick gas check, or "obdurator," a steel
cup which expands in rear of the chamber and
completes the gas-tight joint. The perform-
ance of the gun has satisfied the War Office
authorities of its merits, though the simpler
muzzle-loading system still has the preference,
but at the same time the antipathy to breech-
loading guns has so far abated that it has been
decided to make a wholesale conversion of the
old 32 -pounder smooth bore cast-iron guns into
breech-loading guns and to use them in flank
defences. It has also been found more con-
venient to load these particular guns at the
breech than at the muzzle, chiefly on account
•of its being necessary to mount them on car-
riages which do not recoil ; they will fire heavy
charges of case shot at short ranges.
Armor-Plate Tests.— On Tuesday, an ar-
mor-plate, manufactured by Messrs. Cam-
mell and Co., of the Cyclops Works, Sheffield,
and sub-carbonised according to the patent
of that firm, was tested, by order of the
Admiralty, on board the Nettle, target ship,
in Portsmouth Harbor. Its dimensions were
— 7 feet ten inches, by 6 feet 6 inches; its
thickness 9 inches, and its weight about eight
tons. It was fixed to a transversal wood bulk-
head, built from vertical and two horizontal
layers of oak bulks, making in all 3 feet 6
inches of thickness, the whole being shored by
substantial wooden spalls secured by a massive
wooden thwartship. The gun used was a 12-
ton 9 inch muzzle- loading rifle, and stood be-
hind athwartship wooden bulkhead, 30 feet
from the plate. The charges were 50 lbs. of
battering pebble powder, and the projectiles
shelled Palliser shots, 250 lbs. in weight; the
muzzle velocity being 1420 feet per second, and
the energy at the muzzle 3486 feet. The regu-
lation number of rounds was fired at the plate,
the experiments being conducted by Captain
Herbert, of the gunnery ship Excellent, and
the impact of the three projectiles formed a
triangular diagram, each impact being about
2 feet apart. The first shot struck the centre
of the right hand section of the plate, and
penetrated 7i inches, producing two cracKs
which extended from the point of impact to
either side of the plate, in a slightly downward
direction, and that of infinitesimal width went
through the entire thickness of the plate. The
second projectile was aimed at the middle of
the lower part of the plate. The penetration
was not only equivalent to the thickness of the
plate, but the shot entered 2| inches into the
wooden backing, and considerably enlarged
the two cracks, as well as loosened the left-
hand corner of the plate. The final shot,
however, was the most destructive in its con-
sequences. Besides penetrating through the
plate, and nearly 2 inches into the backing, it
brought away almost one-fourth of the plate.
The disjointure of this section commenced at
the impact of the first shot, and ran in an
irregular horizontal direction to the nearside,
and downwards in a zig-zag fashion to the
centre of the second shot, where it abruptly
branched off to the lower edge of the left side
of the plate. Two additional fissures were also
occasioned in the upper part of the target.
Mr. Wilson was present on behalf of Messrs.
Cammell, and the experiments, which, judged
by comparative data, was fairly satisfactory,
although substantially less favorable than those
with the last composite plate supplied by the
firm, were watched with much interest by the
captain and two chief officers of the German
iron clad Konig Wilhelm.
BOOK NOTICES.
ELEMENTS OP DESCRIPTIVE GEOMETRY. By
J. B. Millar. B. E. London : Macmil-
lan & Co. Price $2.00. For sale by D. Van
Nostrand.
This treatise begins with the elementary
geometry of the plane ; the first chapter con-
taining about the same range of propositions
as the sixth book of Davis' Legendre.
The common problems of, and straight line
and plane in space are given in the second
chapter.
Projections of plane and solid figures and
solution of the spherical triangle form the
topics of chapter third.
Curved surfaces, tangent planes and inter-
sections of curved surfaces occupy chapters
four and five, and complete the subject proper.
Axometric Projection is given in a brief
appendix.
Altogether, it is an excellent work. Con-
cisely written, beautifully printed, with excel-
lent diagrams interspersed in the text.
BOOK NOTICES.
191
METALS AND THEIR CHIEF INDUSTRIAL AP-
PLICATIONS. By Charles R. Alder
Wright, D. Sc London : Macmillan & Co.
Price $ 1.25. For sale by D. Van Nostrand.
This treatise affords a brief outline of the
metallurgy, natural history and industrial uses
of most of the metals.
Chapter I : Describes metals and their
sources. Chapter II : Metallurgy of the pre-
cious metals. Chapter III : Metallurgy of
the more important base metals. Chapter
IV : Metallurgy of the less important oxidiz-
able metals. Chapter V : Physical properties
of the metals. Chapter VI : Thermic and
electric relations of the metals. Chapter VII:
Chemical relation of the metals.
Thirty-three wood-cuts embellish the book.
tixposE des Applications de l'Electricite.
i Par Th. Du Moncel. Fifth volume.
Paris, Lacroix. Price $5.60. For sale by D.
Van Nostrand.
This large octavo is devoted as the title im-
plies to applications of electricity.
The divisions of the subject consider in
order the following topics : Railway Tele-
graphs ; Mechanical Applications ; Applica-
tions to the Arts ; Applications to Domestic
Economy ; Production of heat ; Electric Light-
ning, etc., etc.
Descriptions of machines and processes are
given in the fullest manner.
One hundred and seventy wood-cuts and
three folding plates illustrate the work, which
covers in all 672 large octavo pages.
Water, Air and Disinfectants:. By W.
Noel Hartley, F. R. S. E. , F. S. C. Lon-
don : Society for Promoting Christian Knowl-
edge. Price 50 cts. For sale by D. Van
Nostrand.
This is one of the Manuals of Health pub-
lished by the above society, and it is a work
which should be in every house, as the inform-
ation supplied is of everyday application and
nearly affects the wellbeing of all classes of
society. Much, but not too much, space is
devoted to water, and recent revelations have
shown that the rich as well as the poor in
London are liable to disease and premature
death from impure water. The propagation
of zymotic disease by water receives consider-
ation, and a chapter is devoted to its purifica-
tion. Next we have an inquiry into the pro-
perties and composition of air, and some valu-
able hints on ventilation. It may be thought
by some that it is out of the province of a re-
ligious society to publish a scientific work,
but it does not need much reflection to show
that it is of little use instructing people even
in common morality when their surroundings
are such as may be seen in London and every
large town. It is true that the study of this
work cannot remedy faulty coustruction, but
attention to its advice will do much to mitigate
it. To quote the words of Mr. Simon, lately
the Medical Officer to the Privy Council, " It
is to cleanliness, ventilation and drainage, and
the use of perfectly pure drinking water, that
populations ought mainly to look for safety
against nuisance and infection."
Le Massif du Mont Blanc. Par E. Viol-
let-le-Duc. Paris ; J. Baudry. Price
$ 12.00. For sale by D. Van Nostrand.
The structure, geological and lithological of
Mont Blanc andlhe group of which it is the
culminating point, is the subject of this inter-
esting volume.
It would seem from the amount of detail
in the illustrations, as though every acre of
the area had been carefully studied.
The action of the glaciers in recent times,
as well as the evidences of more extensive
wear by larger ice rivers in past ages, receives
a fairlshare of attention.
The volume contains 275 pages of text,
royal octavo size, and is illustrated by 120
wood-cuts.
There are also four charts exhibiting in
colors the topography of the entire region de-
scribed, with profiles across all the leading
summits.
fPHE Railway Buildeb. By W.vi. J. Nicolls,
I Civil Engineer. New York : D. Van
Nostrand. Price $2.00.
This is a "neat pocket-book for the use of
railroad men ; and is designed to afford ready
aid in estimating the cost of construction of
every portion of the equipment of an Ameri-
can railway.
Special pains have been taken by the author
to render the subject clear to readers who do
not find in the algebraic formula as satisfac-
tory expression of an engineering fact.
To quite a large class of practical railway
men, this plan will be considered as an accept-
able, if not a superior one.
An abstract of the table of contents is here-
with given :
Chapter I. Field Operations ; Corps of En-
gineers ; The Transit ; The Engineer's Level ;
Outfit ; Running a Preliminary Line ; Transit
Book ; Obstacles ; Crossing a River ; Curves ;
Table of Railway Curves. II. Preliminary
Surveys ; Locating the Line ; Grant of Right
of Way ; Form of Contract and Proposal.
III. Cost of Earthwork ; Maximum Grade ;
Staking out the Work ; Average cost of Exca-
vating ; Quantity of Earths equal to a Ton ;
Tunnels. IV. Permanent Way ; Ballast ;
Table of Ballasting ; Stringers ; Cross-ties ;
Iron and Steel Rails ; Tons of Rails required
to lay one mile of Track ; The Open Joint ;
Number of Rails and Joints per mile of Single
Track ; Fish Plates ; Fish Plates and Bolts
required for one mile of Single Track ; Weight
of Hot Pressed Nuts ; Weight of Nuts and
Bolt Heads ; Bolt Heads, and Nuts ; Spikes ;
Contract for Track Laying ; Trestles ; Bridges ;
Weight of Iron Bridges, Wooden Bridges ;
Foundations ; Culverts. V. Frogs and
Switches ; Main Track and Siding ; Switches ;
McCrea's Improved Chair ; Frogs ; Crossings ;
Signals ; Interlocking Signals ; The Block
System. VI. Equipment ; Locomotives ;
Railway Cars ; Sleeping Cars ; Average weight
of Car ; Coal Cars ; Wheels ; Table of Steel-
tired Wheels ; Wrought Iron Frames for
Trucks ; Couplings ; Springs ; Brakes ; Auto-
matic or Continuous Brake. VII. Depots
192
VAN nostrand's engineering magazine.
and Structures ; Passenger Stations; Freight
Depot ; Way Stations ; Flag Stations ; Turn-
table ; Water Stations ; Fuel ; Properties of
Fuel ; Coaling Platform ; Engine House ;
Road Crossings.
MISCELLANEOUS.
The Superintendent of the Westmoreland
Coal Co., writes that a superior form
of Air Duct to be used for ventilating mines,
in connection with a hand fan, is in successful
use in his district. It is a seamless cotton
tube made by the Penn. Cotton Mill, at Pitts-
burgh.
We understand that Mr. E. Roberts, of the
Nautical Almanac office, has been re-
quested by the India office to construct for use
in India a self-acting tide-calculating machine.
It will be designed not only to predict the
tides at open-coast stations, but also river and
shallow-water tides. It will be a great im-
provement on the tide- calculating machine at
South Kensington (now temporarily at the
Paris Exhibition), inasmuch as the tides
caused by the smaller lunar perturbations will
be included. Each component will be fitted
with a slide, so that no error will be caused
from the eccentricity of the pullies. The
ordinates of the curves traced by the machine
being as much as eighteen inches, the use of
the slides is imperative. Mr. Roberts has cal-
culated new numbers to represent the periods
of the many components, and with such suc-
cess, that the actual error of any one compo-
nent, after a run representing a year's predic-
tions, will not exceed the limit of error of set-
ting the component at the commencement.
The machine will be fitted with self -regulating
driving-gear, so that it can be set at the close
of the day and the whole year's curves be
ready for reading off by the next morning.
The machine is expected to be finished towards
the end of the year. Now that the immense
labor (the only objection raised against the em-
ployment of tidal predictions by harmonic
analysis) is superseded, it is to be hoped that
the Admiralty will avail themselves of an in-
strument, the results of which are so vastly
superior to those now obtained with consider-
able labor by actual computation.
A Practical test of a fire-resisting flooring
was on the 6th inst. made in Victoria
Street, Westminster, for the information of
the Metropolitan Board of Works. The Board
has the power to refuse leave to architects to
erect buildings of greater height than 100ft.,
an objection was made to the block called the
"Members' Buildings," in Victoria Street, on
the score of insecurity of life in case of fire.
The objection was met by the provision of fire-
resisting floors, and to prove that the means
taken were secure was the purpose of Thurs-
day's experiment. A square building with 9ft.
brick walls had been erected on the open space
to the west of Westminster Palace Hotel, the
building represented the floor of a house with
windows, doors, and a corridor. A room in
this building contained a quantity of materials
which were set on fire, and burned for up-
wards of an hour. The flooring to be tested
formed the roof of the building, consisting of
ordinary wooden joists, cased with terra cotta
tiles, and there are in the system three open
spaces between the ceiling of the one room
and the flooring of the room above, the room
above in the experimental room being, of
course, open. While the fire was raging in
the room and throwing out an intense heat,
the gentlemen witnessing the experiment
walked above the lighted room, and proved by
the application of the hand to the topmost
terra-cotta tiles that the heat had not pene-
trated, and that the fire was limited in location.
Mr. Francis Butler, the architect of the Mem-
bers'-Buildings, is the inventor, and it is stated
that the invention has the merit of being inex-
pensive, costing about 50s for 100 feet square.
Lieut. G. R. R. Savage, R.E., writing from
Rookee, North-West Provinces, India,
sends us an account of some interesting experi-
ments he has been making on long-distance
telephones. He constructed telephones ex-
pressly for long-distance work, and succeeded
in getting a bugle-call heard distinctly over
400 miles of Government telegraph line, the
wire being one of the four or five main up-
country telegraph wires which are carried on
one set of posts. The telephones used, Lieut.
Savage constructed with about 400 ohms of
No. 38 guage wire, vibrating disc about 2|
inches diameter, the sending vibrating disc
thicker a little than the receiving one. It
seems to him right to oppose the work done
at the receiving end as little as possible by
having a very thin vibrating disc ; while he
had noticed that, ceteris paribus, a thicker disc
approached to a telephone magnet gives a
greater deflection on a distant very sensitive
galvanometer, so long, of course, as it is not
too thick. Lieut. Savage asks the reason for
the following circumstance : Taking off the
vibrating disc of a telephone, and tapping the
magnet with any diamagnetic substance, brass,
glass, &c, the tapping sound is heard distinctly
at a distant telephone. This cannot be caused
in the same way as the current in Prof. Bell's
telephone ; it must be caused, he supposes, by
the particles of magnet being caused to vibrate
longitudinally, and as the coil does not vibrate
in unison with the particles of the magnet, the
permanent lines of magnetic force must be cut
by the coil, and hence a current. Hence, he
asks, if this is the case, might not there be two
causes combined producing the effect in Prof.
Bell's telephone, both approach of disc and
also longitudinal vibrations ? Lieut. Savage
constructed a small induction coil with soft
iron core, the outer and inner coil the same.
He heard and sent messages easily seventy or
eighty miles by joining the two coils separately
in eircuit with the sending and receiving tele-
phone. Of course there was no increase in any
way, as no energy was expended on the cur-
rent by the simple induction coil ; there was
a slight decrease in the sound. He thinks
about 350 ohms of No. 38 wire makes the best
coil for a telephone magnet |inch diameter.
PROPOSED p
/ CAai'leston ffarfivr, &C. at J?t
wiresjyondmq letters and smal§
tM&JViveremadfr wider authority //,
by Capt. XCPost under the orders A/,
PROPOSED
IN'
MOVEMENT OF CBATOEL OF ENTRANCE
RARBOR OFCHARIESTON S.C.
Plate HI
CROSS SECTIONS
Scale for cross sections.
zo 30 40 so 6t> rp so 90 /oe/t.
N?3
N?7
Jowir^txrlinf,
Low JVaterLine -*\*
JBorings at Charleston Harbor, S.C at Jfoints.
indicated by corres_poiidincf letters and smatt circles on Plat&I.
D E F G JL
!N"
[Lint of mean low water
Sklls,sandtdnif
Ctay,pariaSlt in
Surface of Ground
Mte: The- borings at M icJVwere made* under authority of the Light Houses .Board
All the other by Capt.dC.Post under the orders of Lieut Col. (rillmorc
>EDfl
INT
as c-x
/so 4-t
ON O-l
300
J&- 4>oo
0
tt
PROPOSED IMPROVEMENT OF CHANNEL OF ENTRANCE
INTO HARBOR OF CHARLESTON S.C.
Plate n
SECTION C-X
GAP X-Y
SECTION »-Y
Horizontal ScaU '"' ■ '"■ r^g , V, '?", , , ■ «?», , , ,f'A
Plate I.
CHARLES
statute
j
f=r
* . i i
| 4 2 4 0
Meai\ rise and fa
Rise and fall of s
Soundings in fee
mean low wat
VAN NOSTRAND'S
ECLECTIC
ENGINEERING MAGAZINE.
NO. CXVIL-SEPTEMBER, 1878-VOL. XIX.
A PROJECT FOR THE PERMANENT IMPROVEMENT OF THE
CHANNEL OF ENTRANCE INTO THE HARBOR OF CHARLES-
TON, S. 0., BY MEAN'S OF LOW JETTIES.
By Q. A. GILLMORE, Lieut.-Col. Corps of Engineers,, Bvt. Maj.-Gen. U. S. Army.
[ Condensed from Senate Ex. Doc. No. 71, 45th Congress, Second Session.]
THE CHARLESTON BAR.
The bar which stretches bow-shaped
across the entrance into Charleston Har-
bor, from Sullivan's Island on the north
to Folly Island on the south side, has
not varied much in either location, gen-
eral direction, or magnitude, within the
period covered by any trustworthy
knowledge which wTe possess on the sub-
ject.
A comparison of the chart of 1780,
published in Des Barres' Atlantic Nep-
tune, with those of 1821, 1825, and 1851
-'52, "shows that according to the
earliest records the bar of Charleston
has varied comparatively but little in
extent, direction, or in distance, from
the mouth of the harbor."
Measured along its crest, or line of
least depths, the bar is ten miles in
length, its north end on Sullivan's
Island being close up to the entrance or
throat of the harbor, while its south end,
resting on Folly Island, is six miles dis-
tant therefrom. Its average width be-
tween the 18 -foot curves is about If
miles.
In many places the highest points of
the bar are only three to four feet below
the level of mean low-water, although
Vol. XIX.— No. 3—13
the average depths along the crest are
considerably greater.
The main central body of the bar, ly-
ing nearly due north and south, is almost
straight for a length of over five miles,
has its crest parallel to the main shore,
south of the entrance and at a mean dis-
tance of about two miles from it, and is
not at the present time, and, so far as
we know, never has been traversed by
practicable ship-channels.
The northern and southern extremities
of the bar are formed by rather sharp
curves, which connect the straight por-
tion already mentioned with the shore
above and below the harbor.
So far as we can now ascertain there
appears never to have been less than
four, nor more than six, ship channels
across the bar at any one time. The
greatest depth of water has sometimes
been found in one channel and sometimes
in another, being rarely less than 11 J
feet, or more than 13^ feet, at mean low
tide.
The channels, whether four or more,
have always existed in two groups or
clusters, one in the northern and the
other in the southern curved portion of
the bar, and there has always been a
3fean rise and fall of tides
Rise and fall of spring „
Soundings in feet at
mean low water.
194
VAN NOSTRAND'S ENGINEERING MAGAZINE.
deep and broad anchorage inside the
straight reach of the bar abreast of
Morris Island.
This anchorage, sometimes called the
" main channel " and sometimes the
" outer harbor " varies in width from
one-third to two-thirds of a mile between
the 18-foot curves, and in maximum low-
water depths from 20 to 45 feet. The
direction of its central line is about
north and south, and its length from the
throat of the harbor between Morris and
Sullivan's Islands to its southern termi-
nus, where it spreads out in various
channels and shoals in crossing the bar,
is fully five miles. At the extremities
of this outer harbor or basin, several
miles apart, are found the two groups of
channels already mentioned, the most
northerly group being directly in front
of the gorge of the harbor.
The bar is essentially a drift-and-wave
bar, produced in part by the upheaving
action of the waves when they approach
the shore, and are converted by breaking
into waves of translation, and in pari by
drift-material carried along the coast by
surf-currents, especially by those pro-
duced by northeast storms. The pecu-
liar location of the bar, largely to the
southward of the gorge of the harbor,
and the conditions under which a very
large proportion of the ebb-flow is di-
verted from its most direct path, and
forced to skirt the main coast for several
miles before it can find a passage to the
sea, indicate the controlling power of
these storms.
The material composing the surface of
the bar closely resembles that usually
found on the sea-shore between high and
low water in that section of the country,
being shells and fragments of shells, or
silicious sand, or a mixture of them all.
It is easily thrown into suspension by
waves, and is moved by a moderate cur-
rent.
On the north end of the bar five bor-
ings were made in order to determine
the character of the substrata. The
points selected for boring, and the re-
sults obtained, are indicated on the ac-
companying drawings.
It will be seen that below the surface
there are some layers or lumps of mud,
as well as of mud mixed with sand, and
mud mixed with shells.
All the channels which traverse the bar
are, and, so far sa we know, always have
been, ebb-tide channels, produced and
maintained mainly by the scour of the ebb-
current, except Beach (formerly Maffitt's)
Channel, the most northerly of them all,
which lies close to Sullivan's Island.
This is a flood-tide channel, possessing
the usual characteristic of such channels,
that their least depths are always found
near their inner ends, and therefore in
comparatively quiet water. Another
distinguishing feature of such channels
is that from the cross-section of shoalest
soundings inward, toward the harbor,
the descent into deep water is sharp and
sudden, while outward, toward the
ocean, it is gradual and gentle.
The North or Cumberland Channel at
the entrance into Cumberland Sound,
Georgia, and the Coney Island Channel
of New York Harbor are of the same
character. In speaking of the prepon-
' derance of the flood over the ebb in
Cumberland Channel, in my report on
the jetty system as applied to the en-
trance into Cumberland Sound, Georgia,
submitted April 15, 1876, I say :
" The eifect is to make the inner slope
of this part of the bar very steep; the
sand which is rolled along by the flood-
current on the bottom of the outer slope
is first brought to rest in the deep water
of the inner basin. The ensuing ebb-
current, which receives its velocity and
direction from the large volume of
Cumberland Sound, sweeps the inner
slope of the northern shoals longitu-
dinally, and takes up this sand and car-
ries it out by the Amelia Basin, deposit-
ing it upon the main bar. The channel
next to Cumberland Island is therefore
a flood-tide channel, like the Sullivan's
Island or Beach Channel in Charleston
Harbor. They both possess in a marked
degree the steep inner slope which in-
variably characterizes a channel main-
tained by the flood-tide, which having
once passed in is so much diverted in its
direction on the ebb, by the axial line of
the tidal basin, that it cannot flow out in
full volume through the same opening,
but sweeps past its mouth in its passage
to some more direct outlet."
Beach Channel was gauged during
the months of May and June, 1876,
when it was found that on a section
taken 500 yards east of the inner end of
the channel, at the Bowman jetty, the
IMPROVEMENT OF ENTRANCE CHANNEL, CHARLESTON, S. C. 195
volume flowing out during an entire ebb
between the low water line on Sullivan's ;
Island and the 5-foot curve on
Drunken Dick Shoal, amounted to only
48.8 per cent, of the volume flowing in
during an entire flood through the same
section.
On a section taken 930 yards east of
the Bowman jetty, between the low-
water line on Sullivan's Island and the
10-foot curve on Drunken Dick, the vol- j
ume of ebb amounted to 52£ per cent, of
the flood.
CAPACITY OF THE TIDAL BASIN.
The area of the tidal basin formed by
Charleston Harbor, as computed from
the Coast Survey chart and Mills' Atlas
of South Carolina, is about 15 square
miles. This area is assumed to be rilled
during each mean flood-tide by a layer
or prism of water 5.1 feet in height
above the mean low- water level. In ad-
dition to this the adjacent reaches of the
tributary rivers will be filled above their
low-water stage by flood and back
waters, which at the period of slack
water-flood will form in each stream a
wedge-shaped mass resting on the sloping
low-water line of the river, and extend-
ing up to a point where the influence of
the tidal wave ceases to produce a rise
and fall of the surface of the water. The
equivalent of these wedge-shaped masses,
determined by simultaneous tide levels,
together with the water derived from
land drainage during the ebb flow, will
be added to the volume of the tidal
prism above mentioned.
In other words, the total volume of
outflow during each ebb tide, will be
measured by the volume contained be-
tween certain planes of low water and
of high water, throughout the area of
the tidal basin, and up the streams to
points where the tide ceases to be felt,
augmented by the volume derived from
land drainage during the period of ebb
flow.
In order to make a reasonably close
estimate of the volume of outflow, it
would be necessary to determine the
plane of low and of high water, by a
series of simultaneous water levels taken
in the tidal basin and its branches, sup-
plemented by a survey sufficiently in
detail to give the high water and low
water areas of the basin and branches,
and an accurate topography of the mar-
ginal low lands situated between high
and low water.
Xo investigations of this character
having been made at the harbor of
Charleston, the information derived from
the sources above named will be mainly
relied upon in this discussion.
From these data it is estimated that
the average discharge through the throat
of the harbor between Sullivan's and
Morris Islands, on each ebb during the
period of mean rise and fall of tides,
amounts to a little over 3,655,443,686
cubic feet. Of this volume only about
76,571,000 cubic feet is supplied by the
land drainage, on the assumption that
one-half the rain-fall reaches the sea.
This estimate is believed to be not too
large, in view of the fact that the streams
are short and in close proximity to the
points of discharge.
For two or three days during the
period of spring-tides, the average ebb-
discharge will be augmented to about
, 4,228,846,000 cubic feet. The neap dis-
charges, being in smaller volumes than
those pertaining to mean tides, require
no special mention, as any temporary de-
crease of scouring power in the new
channel beyond the jetties resulting
therefrom would be of short duration.
Even if slight shoalinsr ensued during
this period, the maximum depths estab-
lished by mean and spring tides would
be restored on the return of these tides.
The mean duration of the ebb-flow is
taken at six hours, that being the aver-
age of a number of observations made
by Civil Assistant George Daubeney, in
1870 and 1871, the longest flow being
6h 20m, and the shortest 5h 25m.
The average ebb-discharge per second
through the gorge of the harbor during
the period of mean rise and fall of tides is
therefore 169,233 cubic feet (A^j^^Ai.),
and during the period of spring-tides
195,7S0 cubic feet (-4H¥w0JUI), the aver-
age rise and fall at ordinary spring-tides
being 5.9 feet. Xo account is here taken
of the somewhat longer duration of ebb-
flow at average spring-tides.
During very high spring-tides the dis-
charge will be much larger. With a
rise and fall of 10.3 feet (which has
actually occurred), the prism amounts to
about 7,382,562,000 cubic feet, equiva-
lent to 341,780 cubic feet per second;
196
VAJS" NOSTRAND'S ENGINEERING MAGAZINE.
nor will this show the total discharge,
since the marshes will be flooded, and
their area being estimated at eight square
miles, every layer of water over them
three inches thick will add 55,965,870
cubic feet to the prism, or 2,590 cubic
feet to the average discharge per sec-
ond.
It has not been deemed expedient, or
likely to give trustworthy results, to at-
tempt to gauge the flow through the
gorge of the harbor by means of current-
velocities. Those taken some years ago
between Forts Sumter and Moultrie,
with a view of locating channel torpe-
does, proved the existence of eddies and
counter-currents, and other irregularities
of flow, to such degree, especially near
the Sullivan's Island side, that the requi-
site accuracy seemed hardly obtainable
by this method.
There is nothing specially exceptional
in this, for it is known that abnormal
conditions often characterize the flow of
water through the gorge of a large tidal
basin.
It is stated by Mr. D. Stevenson that
at Cromarty Firth, where the waters
pass to and from the sea through a nar-
row gorge, of which the width is about
4,500 feet and the depth about 150 feet:
The mean velocity due to the column of
water passing this gorge, as deduced from the
observed surface-velocity, was not sufficient to
account for the quantity of water actually
passed during each tide, as determined by
measuring the cubical capacity of the basin of
the Firth. This led to the observation of the
under-currents through the gorge by means of
submerged floats, and it was found that during
flood tides the surface-velocity was 1.8 miles
per hour, while at the depth of 50 feet the
velocity was not less than 4 miles per hour,
being an increase of 2.3 miles per hour. Dur-
ing the ebb-tide the surface-velocity was 2.7
miles per hour, and at 50 feet depth it was
not less than 4.5 miles per hour, being an in-
crease of 1.8 miles per hour.
Anomalous variations and irregulari-
ties between the surface and the sub-
current have also been found to exist in
the harbor of San Francisco, Cal., and
elsewhere.
For the foregoing reasons, mainly, it
has been thought best to use the cubical
capacity of the tidal basin and the rain-
fall upon the drainage-area in estimating
the average volume of water which flows
out and in through the gorge of Charles-
ton Harbor.
PLAN OF IMPROVEMENT RECOMMENDED.
It is proposed to construct two low
jetties, one springing from Morris Island
and the other from Sullivan's Island,
converging toward each other in such
manner that their outer ends on the crest
of the bar shall be one-half to five-eighths
of a mile apart. The outer ends of the
two jetties will rest respectively upon
the shoals lying to the northward and
southward of what is known as the
north channel, that being the middle
channel of the north group of three
channels, and having its line of deepest
water located more nearly than either of
the others upon the prolongation of the
axis of deep-water flow through the
gorge of the harbor between Cumming's
Point and Fort Moultrie.
Assuming for the purposes of dis-
cussion the sea ends of the jetties to rest
respectively at X and Y, it seems, in
some measure, immaterial whether they
be established upon straight lines as-
shown at AX and BY, Plate I, or upon
curved lines; and if curved, whether the
convexity be turned toward the central
channel as at CX and DY, or from it, as
at EX and FY. In either case, if kept
at the proper heights, they will produce
an ebb-flow through the gap able to
maintain a deep channel through the
bar. Neither the straight jetties, how-
ever, nor more especially those with
their convexity turned away from the
channel, act as training-walls to guide
the outflowing water. The curved jet-
ties convex toward each other, being less
open to this objection, are the ones
adopted in this project.
The north jetty starts from a point on
Sullivan's Island 1,800 yards east of
Bowman's jetty. The half next the
shore is curved to a radius of about Ij
miles, the outer half being very nearly a
straight line. The total length of this
jetty from C to X is 7,450 feet, and its
general direction is southeast.
The south jetty, having a total length
of 11,050 feet from D to Y, starts from
Morris Island at a point about 650 yards
from Cumming's Point, its general direc-
tion being east. The shore end is curved
to a radius of about three miles for a
little more than one-half its entire length-,
while the half next the sea is nearly
straight, as in the case of the north jetty.
The specified length of the jetties is
IMPROVEMENT OF ENTRANCE CHANNEL, CHARLESTON, S. C. 19?
taken for purposes of discussion. As
will be seen hereafter, they would not be
able to produce a channel of the requisite
capacity through certain materials which
are likely to be encountered in the bar,
although they would be expected to main-
tain such a channel if once established.
The outer ends of the two jetties
slightly converge toward each other as
they approach the crest of the bar, and
are intended to act as training-walls for
a distance, in each case, quite equal to
half its entire length. These portions
lie in the direction of the flood-currents,
and may be built to any height without
obstructing the inflow. For fully one-
fourth of their entire length the sea ends
could be carried above the level of high-
water, so as to be visible at all stages of
the tide.
The characteristic feature of the de-
sign—that of low jetties — is intended to
maintain the bar in its present general
location, with such moderate increase of
magnitude as may be expected to result
from concentrating upon a gap one-half
to five-eighths of a mile in width, a portion
of the water which is now dispersed over
a width Qf ten miles.
The complete success of the works is
believed to depend on three important
conditions, which they are expected in
great measure to satisfy, and which have
been kept in view in preparing the de-
sign, viz :
1. They should not impede the inflow
to such degree as to prevent the tidal
basin being filled as now at every influx
of the tidal wave.
To this end the inner half of each
jetty, more especially its central portion,
located in deep water across the thread
of the current, is kept several feet below
the water. The outer half, being nearly
parallel to the direction of the flow, is
built higher, and the sea end, for a dis-
tance of several hundred feet, may be
carried up to high water level, or higher.
2. They should control the outfloio to
■such degree and in such manner that a
channel of the required depth will be
maintained through the bar.
To this end, although a large portion
of the surface flow will spread out over
the tops of the jetties and thence over
the bar, the central flow, throughout the
entire depth along the axial line of the
gorge between Sullivan's and Morris
Islands, is aided in its natural tendency
to reach the sea along the prolongation
of that line, by the opening left for it
between the jetties. The bottom-flow
through the gorge of the harbor is de-
flected on converging lines by the jetties,
and is therefore forced in a measure to
concentrate itself in, and flow out
through the gap between them. The
outer half of each jetty and the adjacent
portion of the shore end act as a training-
wall for this flow.
3. They should not to any considerable
extent cause a movement seaward of the
main body of the bar y that is, the gen-
eral position of the bar shoidd be inde-
pendent of the effects produced between
and beyond the heads of the jetties.
It is believed that this condition will
be secured by making the shore ends of
the jetties low for at least one-half their
length, or throughout those portions
which cross the thread of the current in
deep water, so as to allow the tide to ebb
and flow somewhat freely over them.
The effect of high jetties, with a cor-
respondingly wide gap between them to
allow a full influx of the tide, would
tend to transfer the gorge of the harbor
from its present position to the sea ends
of the jetties, two and a half miles
distant, and move the shore line out to
that point, by causing a filling in of the
exterior angles between the jetties and
the shore. After reaching this stage, a
drift-and-wave bar would probably be
found to the seaward of the present bar,
in front of the jetties, rendering it neces-
sary to extend them in order to cut a
passage through it.
It seems essential, therefore, that the
agencies which maintain the present bar
should remain in as full force as possible,
consistent with the requisite concentra-
tion of outflow between the jetties.
The probable effects will be that the
bar will be raised somewhat throughout
its entire length, the waves will break
upon it more frequently than now, and
considerable shoaling will, of course,
take place in Beach Channel and in all
the southern group of channels. But it
is believed that the important condition
of keeping the bar generally in its pres-
ent position will be secured.
The drift- material carried along the
coast by surf-currents, as well as the
sand thrown up by the breakers on the
198
VAN nostrand's engineering magazine.
north and south shoals, instead of lodg-
ing in and filling up the exterior angles
between the jetties and the shore, as in
the case of high jetties, will be disposed
of in a harmless manner.
For example, a heavy northeasterly
storm, producing breakers along the
north shoal, and strong southerly surf-
currents along the shores of Long and
Sullivan's islands, would put in motion a
large quantity of material, a portion of
which would be carried in by the flood-
currents over the north jetty and through
Beach Channel, coming to rest in the
deep water of the main channel. It
would next be taken up by the ebb cur-
rent and rolled out to sea between the
jetties. Beyond the jetty-heads it would
encounter the littoral ebb-current, mov-
ing to the southward with a velocity
accelerated by the storm, by which it
would be again carried in a south-
westerly direction until finally, left to
the action of the south breakers, it would
be either deposited temporarily upon the
south shoal, or carried still farther to
the southward. This action, which
would be incessant during the continu-.
ance of the storm, is illustrated in
Figure 1, Plate III.
The action of a southerly storm would
be the reverse of this. In either case
some drift-material would be carried by
waves and surf-currents around the
jetty-heads, and would subside in the
deep water between them, to be swept
out by ensuing ebb- currents, and dis-
posed of to the northward or southward,
according to the direction of the storm.
This movement of sand was referred
to in my report on the improvement of
the Fernandina Bar, submitted April 15,
1876, from which the following extract
is made:
As a moderate assumption, a northeaster of
three days' duration might be expected to
lower the north shoal four inches within the
area covered by the breakers. The greater
part of the eroded material, amounting to up-
ward of 516,000 cubic yards, would doubtless
be distributed along the south shoal during
the progress of the storm. If the waves should
subside, or a southerly or southeasterly storm
set in before the bar channel had returned to
its nominal condition, the material subsequently
carried out would not reach the south shoal,
but in the former case would remain near the
outlet on the outer slope of the bar, and in the
latter would be carried back by the waves to
the north shoal. If as much as one-fourth of
it remained in the bar channel between the
inner and outer eighteen foot curves, a few
severe storms such as frequently occur within
the period of a single month would entirely
destroy it, by filling it up to the level of the
shoal on either side.
It would appear, therefore, that millions of
cubic yards of the material composing the bar
might be shifted back and forth from one side
of the channel outlet to the other during a sin-
gle season, without causing injury to the chan-
j nel by shoaling, and without producing any
| changes in the form and location of the bar
itself, that might not entirely escape the notice
I of the most careful surveyor. And yet this
j shifting of material of which no evidence may
be left behind, should enter as an important, if
not a controlling function in the project of the
j engineer, because the useful life of his works
| is more or less dependent thereon.
As no works can be expected to 3top
this movement of drift-material for any
| great length of time, they should, if
! practicable, accommodate themselves to
I it under conditions of a permanent char-
| acter. Those proposed are designed to
do this, by allowing the drift-sani to
I move from one part of the bar to the
other in much the same manner as now,
never remaining in the jetty channel
longer than a few tides, and never find-
ing a resting-place anywhere that the
next storm may not disturb.
PROBABLE EFFECT PRODUCED BY THE
JETTIES.
An attempt is made below to deter-
mine by the use of appropriate formulae
the principal phenomena of the ebb-flow,
after the jetties shall have been con-
structed and an enlarged water-way of
the greatest self-maintaining area has
been established between them, and the
hydraulic equilibrium has been restored.
The jetties in this discussion are first
assumed to occupy the lines CX and
DY, Plate I, with their respective crests
established at the varying heights shown
by the longitudinal sections CX and DY
on Plate II, the sea ends being half a
mile apart. The north jetty crosses the
deep water of Beach Channel at the level
of twelve feet below mean low-water,
I the crest being held at that level for a
I length of about 650 feet, whence it rises
gradually by gentle slopes to high-water
! at each end. On the sea end the part
! carried to high-water level is 1,500 feet
j long.
The south jetty, designed on a similar
1 plan, crosses the main channel on a level
IMPKOVEMENT OF ENTRANCE CHANNEL, CHARLESTON, S. C. 199
fifteen feet below mean low-water, the
seaward end for a length of 2,000 feet
having its crest at high -water.
The sectional area of the gorge profile
between Morris Island and Sullivan's
Island is as follows :
Square feet.
Area of low-water section. . . . 159,550
Area of high-water section. . . 195,350
Mean ebb-tide area 176,600
The width of the surface at half tide,
corresponding to the mean ebb-tide area
is 6,825 feet, and the wetted perimeter
6,927 feet. The hydraulic radius is,
therefore, 25.46 feet.
At mean low-water the surface width
is 6,750 feet, the wetted perimeter 6,851
feet, and the hydraulic radius 22.29 feet.
The area inclosed between the line of
gorge at Cumming's Point (Morris
Island) and that of the proposed jetties
and gap is 2.16 square miles.
The average discharge per second
across the proposed sites of the jetties
and the gap between them is, therefore,
183,451 cubic feet
73,655,443,886 + 307,1@8,434\
\ 21,600 /
or 14,218 cubic feet more than the
amount flowing out at the gorge.
The following are the sectional areas
in square feet now existing on the lines
proposed for the jetties and gap :
r=hydraulic radius in feet.
In the gorge at Cumming's Point the
grand mean of all the velocities is .958
, /169,233\
teet per second I— ).
1 \176,600/
The grand mean of all the velocities
with which the water passes through
the various compartments of the present
section along the line of the jetties and
i ojap is O.o9212 feet per second ( — - I.
|& F l \309,817/
The mean hydraulic radius of this
aggregate section is 14.0322 feet
/ 309,817
\ 7,574.3 + 2,679.7
i-
11,825,
Therefore
Y =0.59212 = 100 a/14.0322Xa/£
0.59212
Va=
: = 0.0015SO
Low water.
Mean half
tide.
Square feet. Square feet.
Line of north jetty, i 59,900 78,880
Line of south jetty.; 171,720 201,365
Gap 22,840 29,572
Totals '. 254.460
309,81'!
For the following calculations the
D'Aubuisson-Downing formula will be
used, not because it is the best, but
mainly because it is very simple and
easy of application. It is, moreover,
believed to answer very well in cases of
broad open streams.
The formula is
V=100 X y^X \A> in which
V= velocity in feet per second.
s= slope, or ratio of horizontal length to
vertical descent.
100 XV 14.0322
s= 0.000002498.
On the assumption that this slope is
! the same throughout the section (which
; in point of fact is not precisely the case,
I and we have no data for making the
'■ necessary correction for the several com-
partments), the total average volume of
discharge per second, amounting to
183,451 cubic feet, is distributed as fol-
lows, as determined by the various areas
and hydraulic radii:
Cubic feet.
Through present section on site of
north jetty 39,418
Through present section on gap 15,227
Through present section on site of
south jetty 128,806
Total as above 183,451
This will be assumed to represent the
present distribution of the outflow per
second through the section selected for
the sites of the works and the opening
between them at its narrowest point.
The changes of regimen which the
jetties will tend to produce, and the area
of the water-way which once established
they would be expected to maintain be-
tween and beyond the sea ends, will next
be considered.
The north jetty will reduce the half-
tide area of the water-way from its pres-
ent area of 78,880 square feet to 41,593
square feet, and the hydraulic radius
, from 10.41 feet to 7.59 feet.
The south jetty half-tide water-way
200
VAN NOSTRAND7S ENGINEERING MAGAZINE.
will be reduced from the present area
of 201,365 square feet to an area of
94,684 square feet, and its hydraulic
radius from 17.03 feet to 10. 7 7 feet.
These hydraulic radii are to be con-
sidered permanent, the crests of the
jetties being supposed to be able to re-
sist abrasion by the current.
In the gap, where alone erosion can
take place, the present mean half-tide
water-way is 29,572 square feet, and the
mean low-tide area 22,840 square feet.
After the jetties shall have achieved
their maximum scour, aided by dredging
or other artificial appliances wherever
clay-beds are encountered, and the
equilibrium of flow is resumed, the origin-
al general average slope S= 0.000002498
will be restored.
The aggregate average discharge per
second before the jetties were built will
also be restored.
From these premises the following
average discharges per second are found:
Cubic feet.
Across crest of north jetty 18,113
Across crest of south jetty 49,110
Total over the jetties 67,223
The balance of the discharge, amount-
ing to 116,228 cubic feet per second
(183,451—67,223), will go out through
the gap between the jetties, where at
present there is a mean half -tide area of
only 29,572 square feet and a mean dis-
charge of 15,227 cubic feet per second.
The formula already used gives for the
average velocity through the gap:
V=ioox V*x W
Substituting the value Vs= 0.0015807,
we have
V=0.15S07xA/r
The value of r is unknown. The width
of the gap being 2,640 feet, we have for
the wetted perimeter, by General Abbot's
rule, 2,680 feet (2,640X1.015).
If A represent the unknown half -tide
area of the gap in square feet, we have
_ A
~2,680
and VA
?; = 0.1580'7y
a/2,680
The calculated average discharge
through the gap per second being
116,228 cubic feet, we have
116,228=Av=.-Ax\/AX
0.15807
V2,680
=V(
116,228x^2,680'
0.15807 /
A= 113,160 square feet.
The mean hydraulic radius at the gap
will therefore be 42.22 feet (— 3-l^-0>i at
V 2,680 /
mean half tide, or 39.71 at mean low-
water. This implies very considerable
mid-channel depths.
In the profile between Fort Sumter
and Sullivan's Island, having a mean
low-water area of 177,620 square feet, a
width of 4,960 feet, and a hydraulic
radius of 35.28 feet, fully ninety per
cent, of the total area pertains to depths
of twenty-four feet and upward, occupy-
ing a width of 3,540 feet, in which the
maximum depth is seventy-six feet.
On the profile from Cumming's Point
to the Bowman jetty, the low-water area
is 159,550 square feet, the width 6,750
feet, and the hydraulic radius 23.29 feet.
The compartments of twenty-four feet
depth or more form eighty per cent, of
the whole section, and occupy a width of
3,000 feet, with maximum depths close
up to seventy feet.
In the new channel between the jetty-
heads, where the hydraulic radius is
39.71 feet, it may be expected that the
area of depths of more than twenty-four
feet will constitute a very large propor-
tion of the total area of the gap, and that
maximum depths of seventy-five feet
and upward would be maintained in mid-
channel.
The average velocity from which the
general average slope is derived is, of
course, less than the velocity that will
prevail in the deep channel compart-
ments of the profile, since with unaltered
slope the velocities in different portions
of the profile may be considered to vary
as the square root of depths. The grand
average velocity in the profile between
Cumming's Point and Bowman's jetty,
with a mean hydraulic radius at half
tide of 25.46 feet, is .958 feet, per
second; in the 50-feet compartments the
average velocity would be 1.33 feet per
second; while during the second and
third quarters of ebb the velocities will
vary between two and three feet per
second.
IMPROVEMENT OF ENTRANCE CHANNEL, CHARLESTON, S. C.
201
The bottom velocities will generally be
but little less, to judge from the results
of a great number of current observa-
tions made near Fort Sumter by Capt.
William Ludlow a few years ago.
Of the effects that will be produced to
the seaward of the jetties upon the
outward slope of the bar, by so large a
volume of outflow, it is impossible to
deduce from formula?, results upon which
reliance can be safely placed. We
know what kind of effects will ensue,
but we have no precise measure of their
intensity. The first and greatest diffi-
culty met with is the want of trustworthy
data concerning the rate at which the
water, as it issues forth from the gap,
will spread out and disperse over the
descending outer slope of the bar, with a
diminishing velocity and scouring power.
For the purpose of discussion, it will be
assumed that the currents having passed
the jetty-heads will spread out in a fan-
shaped area, at an angle of thirty
degrees on each side, with the axis of
the new channel. The chart seems to
indicate that this angle is not too small.
It is, however, largely conjectural.
Assuming, however, a total spread of
sixty degrees, the width of the profile lj
miles to seaward, through which the out-
flow from the jetties is supposed to pass,
is ] 0,933 feet.
By adding the fan-shaped water-prism
between the jetty-heads and the sea-
ward profile to the volume of flow
through the former, we find that the
average volume passing through the
outer profile will be 128,916 cubic feet
per second.
The half-tide sectional area of the pro-
file is found, by the method of calcula-
tion already employed, to be 172,312
square feet. Its wetted perimeter is
11,097 feet, its hydraulic radius at mean
half -tide 15.52 feet, and at mean low-
water about 13 feet, which implies more
than ample mid- channel depths through
the outer slope of the bar for vessels of
the deepest draught.
As this outer profile is taken upon the
seaward slope of the bar a little beyond
the eighteen foot low-water curve, the
permanent depths first secured there —
permanent because representing a re-
stored equilibrium — can, of course, be
increased at pleasure, and at a small re-
lative cost, by the moderate extension of
the jetties.
If the gap between the jetties be
widened, the submerged portions must
be raised to a greater average height,
thus diminishing the area of water-way
above them, in order that a channel of
the same mean depths in the seaward
profile near the outer eighteen foot
curve, above deduced for a specified
height, may be maintained. Considera-
tions of cost furnish strong arguments
for keeping the crest of the jetties low,
as the expense of added height in jetties
with side slopes increases much more
rapidly than the height itself. For ex-
ample, a wall ten feet high and ten feet
wide on top, with slopes of forty -five
degrees, contains 200 square feet in cross
section, while a wall of the same width
on top and only twice the height con-
tains three times that area of cross-sec-
! tion. By doubling the height the quan-
I tity of materials required is therefore
trebled in this case, and more must be
i still added to compensate for the in-
creased subsidence caused by doubling
the weight on the foundation. By
I trebling the height we get six times the
I area of cross-section.
With an opening between the jetties
| five eighths of a mile wide, established by
| swinging the south jetty to the south-
ward around its shore-end as a center
i until it occupies the line DZ, and leaving
' the north jetty located on the line CX,
■ as before, it will be necessary to raise
I the submerged portions an average of
! about 14 inches higher than the crests
I shown on the longitudinal sections CX
I and DY, Plate II, in order to maintain
j in the seaward profile l-£ miles from the
! jetty-heads, the same hydraulic radius
| deduced for the half-mile gap. Between
the jetty-heads the hydraulic radius
for the five-eighths mile gap would be
about 4.45 feet less than for the half-
| mile gap. Under both suppositions the
| sea-ends of the jetties rise to high-water
| level for a length of 1,500 feet on the
north jetty, and 2,000 feet on the south
| jetty.
There seems to be little room for doubt
| that a channel of ample capacity having
! been once established through the bar, it
| will be permanently maintained by the
| jetties, and that the materials more or
i less constantly carried out by the current,
202
VAN NOSTKAND'S ENGINEEKING MAGAZINE.
especially during the prevalence of drift-
producing storms, and immediately sub-
sequent thereto, will not be deposited
under conditions favorable to the forma-
tion of an exterior bar.
The outer slope of the bar, directly to
the seaward of the jetties, will perhaps
assume and maintain a salient form in
consequence of the materials being first
brought to a temporary rest at that
point ; but unless the main body of the
bar to the northward and southward of
the jetties also moves bodily to the sea-
ward in a marked degree, in violation of
all known or suspected laws, the move-
ment of drift will go on substantially as
at present, finding only a transient rest-
ing place in front of the new channel, or
upon any other portion of the bar.
Having assumed the width between
the jetties and the points on the bar at
which their sea-ends should rest, it is not
claimed that the corresponding height
capable of maintaining through the bar,
to deep water on the outside, a channel
of a specified capacity, can be determined
with precision by computations based on
the use of any known formulae. But it
seems quite clear, with the large surplus
of available water not needed between
the jetties, that we can by first building
them low throughout their entire length,
and then raising them gradually to the
required height, utilize the flow, and ac-
complish the desired results, not only
with certainty, but with the greatest at-
tainable degree of economy.
It will be expedient, from other con-
siderations, to proceed gradually in
raising the works to the requisite height.
It will be seen from Plate III, containing
a record of the borings, that at the point
D, nearly in the axis of the new channel,
and a little outside a right line joining
the sea-ends of the jetties, a bed of
" soft mud and sand," 7 feet in thickness,
is encountered at a depth of 5 feet below
the bottom, and 17 feet below mean low
water. It overlies a bed of sand 4j feet
thick. At E about 460 yards to sea-
ward of the point D, and also in the line
of the new channel, a layer or thin bed
of sand, shells, and soft mud, only 1 foot
thick, is found 1 foot below the bottom,
and 13 feet below low water. At
a depth of 6| feet, a 1-foot bed, or lumps
of stiff clay exist, resting on 10^ feet of
fine sand. At A, more than 1^ miles in-
side the jetty head, and a little to the
northward of the probable line of
deepest water, a bed of tenacious clay is
found 4 feet below the bottom, and 18
feet below low-water, while outside the
gap at F, about half a mile in a souther-
ly direction from D, no clay or mud is
found until a depth of 28 feet belpw
low water is reached, and there it is only
a foot thick, and rests upon 3 feet of
" shells and sand."
These borings show that the material
which may be found capable of resisting
erosion and removal by the currents does
not occur in continuous and regular
strata, but apparently in detached sheets,
lumps, and beds, varying greatly in
thickness and in depth below the bottom,
and below the water-level.
It is presumed that none of the mate-
rials which it would be necessary to re-
move, in establishing a deep water-chan-
nel through the bar, can be eroded and
carried off by the currents, except those
designated in the table of borings as
" shells," " sand," " soft mud," or a mix-
ture of two or all of them. Whenever
stiff clay is to be removed some method
of dredging or harrowing will have to be
adopted, and it may be necessary to re-
sort to harrowing in aid of the natural
scour, to get rid of some of the beds of
mud and softer clays. The sand and
shells will be carried out by the current.
When the jetties, supposed for the
present to be built of riprap resting on a
mattress of fascines, have reached their
full length, or rather their assumed
length, from the shores to the points X
and Y, respectively, with heights through-
out the submerged portions not much
greater than may be deemed necessary
to secure the foundations from injury by
undermining, the lower sections should
then be gradually built up until a suffi-
cient flow is established between them to
scour off the surface-layer of sand, shells,
and soft mud, and lay bare the beds of
stiff mud and clay between the heads of
the jetties, and as far beyond them as
possible, consistent with the safety of
the works themselves. The greatest
effect will naturally be produced along
the center line, and the volume of flow
should not be made large enough to
cause any considerable scour along the
faces of the jetties.
Dredging, if it becomes necessary at
IMPROVEMENT OF ENTRANCE CHANNEL, CHARLESTON, S. C. 203
all, should begin along the line of great-
est scour as soon as the removal of the
clay by that method becomes practicable,
and as greater depths are secured in this
manner the jetties should be raised to
higher levels.
The borings indicate that sooner or
later, during this stage of progress, it
will become necessary to determine in
what manner the needed depths to sea-
ward upon the outer slope of the bar can
best be established. It may be done
either by enlarging the area of the water-
way between and directly in front of the
jetties, so as to lengthen the outward
reach of the scouring power, or by ex-
tending the jetties themselves further out
on the bar, with only moderate depths
between them, thus carrying further to
seaward the point at which divergence
and consequent loss of power begin. In
the degree to which the first method, if
adopted, is carried into execution, will
the jetties approach the heights shown
in sections CX and DY, Plate II, and
they could not theoretically attain and
exceed those, heights until the channel in
the gap has a mean half-tide area of
113,160 square feet, and a hydraulic
radius of 42.22 feet. This implies, as al-
ready stated, a deep central channel with
maximum depths, which would perhaps
be impossible of attainment at moderate
cost by any known process of dredging
or raking.
The boring at D, in the line of the new
channel, indicates that very little dredg-
ing or raking would have to be done to
reach a depth of 31 feet below mean low-
water, there being only 6 inches of stiff
clay to penetrate in that distance, and
that is found at a depth of 2S-|- feet. At
E, farther out on the same channel line,
only 12 inches of stiff clay is encountered
in a depth of 30 feet. Whether this
material occurs nearer the surface, or in
thicker beds, at other points where its
removal would be necessary to give the
requisite water-way, cannot, of course, be
known from the examinations that have
been made. Very numerous borings
taken near each other would be necessary
before even a very general estimate could
be made of the quantity of materials of
different kinds that would require re-
moval by other agencies than the natural
scour, in order to attain any given area
of water-way.
It is probable that the thin deposits of
clay encountered in boring are only de-
tached lumps or small masses that will
be no obstacle to the prosecution of the
work, but will settle down to lower levels
as the sand is scoured away from around
and beneath them. The existence of
such lumps on the bottom of the inner
harbor has been reported by divers.
For the purpose of this estimate, max-
imum mid channel depths in the gap of
only 31 feet at mean low-water will be
adopted, because that depth appears to
involve only a small outlay for dredging,
and possibly none at all.
By fixing the crests of the submerged
portions of the jetties at the requisite
heights, we have the means of maintain-
ing in this water-way average depths not
much less than the maximum depths,
thus producing a wide channel with mod-
erate depths, instead of a narrow channel
very deep along the central line and
shoal toward the sides. Under these
conditions the hydraulic radius in the
gap can be made comparatively large.
It will be taken at 24 feet mean half-
tide.
It appears from calculations based, as
before, on an assumed divergence of 60
degrees in the ebb flow exterior to the
jetty-heads, that a normal flow through
the half-mile gap, with a hydraulic radius
of 24 feet, cannot maintain a channel ex-
ceeding 21 feet in depth at mean low-
water, for a greater distance than about
5,500 feet beyond the heads of the jetties
where the divergence begins. This
would require the jetties to be 2,400 feet
longer than jetties CX and DY, already
discussed, although their submerged
crests would be somewhat lower.
The north jetty, if kept generally paral-
lel to the bottom, would not exceed 1
foot in average height, its onice being
mainly to prevent the enlargement of the
i Beach Channel water-way by scour.
; The south jetty would have its submerg-
j ed crest at 10. 78 feet below mean low-
water, if kept level throughout. Under
these circumstances, with a 24-foot
hydraulic radius in the gap, and corre-
sponding hydraulic radii in the seaward
profiles, on the supposed total divergence
of 60 degrees, the original slope will be
restored. The mean average ebb velocity
through the gap will be 0.93 foot per
second.
204
VAN NOSTRAND'S ENGINEERING MAGAZINE.
By raising their submerged portions
above the calculated heights, last men-
tioned, greater ebb flow and velocities
would be established in the gap, with
correspondingly increased power and
outward reach, and, therefore, increased
depths through the outer slope of the
bar into the deep water beyond. But
this would give no greater depths in the
gap, under the supposition that beds of
clay exist there at and below the depth
of 31 feet, the only condition which ap-
pears to impose the necessity of low jet-
ties at all.
If the submerged crests be placed at
the varying heights shown in sections
CX' and DY', Plate II, the total areas
over the jetties and through the gap will
be somewhat diminished, and as the areas
are all fixed, while the volume to be dis-
charged remains the same, there will
ensue in the gap a banking up of the
waters and consequently an increase of
slope and of velocity. The computations j
show that the natural slope of 0.000002493
or about ^ inch to the mile, will be in- 1
creased to 0.000004963, equal to about
T5g- inch per mile; and the previous mean
average velocity of 0.93 foot per second
will be augmented to 1.09 feet per sec-
ond. At what distance beyond the jetty-
heads the original slope will be resumed
cannot be ascertained by any process of
computation, and consequently the dis-
tances beyond the points X and Y, to
which the jetties should be carried in
order to maintain a channel of the re-
quired depth through the outer slope of
the bar, is largely conjectural. It is cer- 1
tain that they will not have to be extend- !
ed as far as in the case of the low jetties |
last discussed. The calculations show,
however, that, with the assumed diverg-
ence of 60 degrees, the heads of the jet-
ties, or the point where divergence begins,
need not be located more than 1,390 feet
■to seaward of the points X and Y, Plate
I. This, theoretically, places their heads
at X' and Y', respectively.
The practical solution of this question
would of course be given by a gradual
and cautious building up of the jetties,
with frequent observations, of their
effects, care being taken that they are
not raised so high as to prevent the
complete filling of the tidal basin by
each flood.
Additional borings would of course be
made before definitely fixing the width
between the jetties, as it is possible that
beds of material incapable of removal
by natural scour may exist at such
moderate depths that the half-mile gap
should give place to a considerably
wider one, a question which will doubt-
less turn mainly on the quantity of
materials that may require to be exca-
vated by dredging.
No change of this character and for
this purpose, if judiciously made, would
materially alter the estimated quantities
of materials needed for the construction
of the works.
The volume of water, a little more
than thirty-six hundred and fjfty-five
millions of cubic feet (3,655,374,296),
which is supposed, in the foregoing dis-
cussion, to pass out through the gorge
of the harbor on each ordinary ebb-tide,
is believed to be less than the actual
outflow of one tide.
Computations, in all respects similar to
those given above, have been made on
the supposition that the volume of out-
flow during each or ordinary tide, is
4,834,000,000 of cubic feet, which is be-
lieved to be somewhat in excess of the
actual outflow.
The computed hydraulic radius in the
gap between the jetties, is the same in
both cases, which was to be expected, for
the reason that we have only the calcu-
lated slopes and mean velocities to deal
with, and that these vary with the vol-
ume of flow through the same section.
The actual slope and velocity may be
assumed to lie somewhere between those
deduced in the two cases, and therefore,
to correspond to the deduced hydraulic
radius. These theoretical results are of
practical value only when they point to
bottom velocities possessing a scouring
power of sufficient intensity to maintain
the new channel. In the case under dis-
cussion, they theoretically satisfy that
condition. Greater velocities could, of
course, be established between the jetties
by raising them higher, and in the sea-
ward profile by extending them further
out upon the bar.
It is quite likely that there would be
an advantage in locating the sea-ends of
the jetties about one-fourth of a mile to
the southward of the points indicated
on Plate I. This would place the center
of the half-mile gap at the point Y,-
IMPROVEMENT OF ENTRANCE CHANNEL, CHARLESTON, S. C.
205
where the sea end of the south jetty is
placed in the drawing, and would turn
the axis of the new channel more away
from the prevailing storms which come
from the northeast. The jetties in these
positions are shown in Plate I, by heavy
broken lines. It is not intended in this
project to fix definitely either the length
or the height of the jetties, or their pre-
cise location or distance apart, but to
submit a general plan of improvement
by means of submerged jetties that shall
have their crests, throughout those por-
tions which cross the thread of the cur-
rent, at a height corresponding to the
least width of the gap between them,
the objects sought by this method being
to lessen the first cost of the jetties, and
to obviate the necessity of their subse-
quent extension.
The foregoing discussion will be
revised, if necessary, in a supplement-
ary report, as soon as the actual veloci-
ties have been ascertained by observa-
tion, and the requisite borings have
been made.
CONSTRUCTION AND ESTIMATES.
The jetties to which the following
estimates apply are those last discussed,
located on the lines CX' and DY', Plate
I. The varying heights to which they
rise above the bottom are shown by
heavy parallel hatching in longitudinal
sections CXX' and DYY', Plate II.
Their sea ends for a length of 3,000
feet on the north jetty and 3,500 feet on
the south jetty have their crests at the
level of half flood of spring-tides, or 3
feet above mean low-water.
The total length of the north jetty is
8,480 feet, and that of the south jetty
13,040 feet. These are theoretical
lengths. In practice it will probably be
found necessary to give some additional
length. They are to consist of a super-
structure of riprap stones with rather
low side slopes resting on a mattress of
fascines 2 feet thick.
The slope on the exterior faces of the
jetties will be 1 upon 2 throughout their
entire length. On the interior faces it
will be 1 upon 1-J, except on the sea ends,
where, for a distance of about half a
mile, it will be 1 upon 2.
For the north jetty the minimum
width on top is 15 feet. This is in the
lowest portion where it crosses Beach
Channel. From that point outward, the
width increases to 24 feet, which is-
adopted for that portion which rises
above mean low-water level.
The south jetty has a minimum width
of crest of 12 feet where it crosses the
main channel, at depths varying from
10 to 15 feet belo^jv mean low-water.
Thence outward the width increases to
24 feet for the highest part, as in the
case of the north jetty.
It cannot perhaps be safely assumed
that beds of clay which may be encoun-
tered near the surface are sufficiently firm
to resist the weight of the works, with-
out considerable subsidence. Where
such beds, however, are overlaid by a
thick stratum of sand, or a mixture of
sand and shells, no great disturbance
may be expected.
Where the jetties are constantly sub-
merged, they will not exert a pressure
upon the mattress foundation exceeding
91 pounds per square foot for every foot in
height, to which must be added, where Ihe
work rises above low- water level, about 59
pounds more for each foot in height dur-
ing the time they are out of water. This
takes no account of any lateral distribu-
tion of weight, which must in a greater
or less degree take place in riprap con-
structions.
There being only two points where the
actual pressure upon the bottom will ap-
proach near to one ton per square foot,
while it will generally fall below one-half
ton, it is believed that no settlement or
disturbance of a very serious charac-
ter will be likely to take place. At the
two points referred to, in the main chan-
nel, both weight and cost could be re-
duced by replacing a portion of the
hearting of the jetty with mattresses
similar to those used for the foundation,
as shown in Fig. 2, Plate II, care being
taken to keep the wood well inside the
riprap, so that after -the voids in the lat-
ter have become filled with sand, it
would be safe from the ravages of worms.
During the progress of work the voids
could be filled at moderate cost by pump-
ing sand from the bottom near by.
Riprap suitable for the entire work,
except the facing of the sea ends of the
jetties, can be procured for $3.75 to $4.00
per cubic yard, measured in the jetties.
The stone for facing should be rather
large, and will cost $5.50 to $6.00 per
206
VAN JSTOSTRAND'S ENGINEERING MAGAZINE.
cubic yard. The foundations of mat-
tresses or poles, can be laid for about
$1.00 per square yard.
Twenty to twenty-five per cent, would
be a fair estimate for additional riprap,
required to compensate for subsid-
ence.
A liberal allowance of dredging and
raking in the new channel, in material
not susceptible of removal by the scour
of the current, would be $150,000.
Due account being taken of contin-
gencies, the total cost of both jetties
may be stated at $1,500,000 to $1,800,000.
EXPLOSION OF A WESTERN RIVER STEAMER.
By JOHN W. HILL, M. E.
Written for Van Nostkand's Engineebing Magazine.
On the night of May 17th, .876, the
steamer Pat Cleburne, of the Evansville,
Cairo and Memphis Packet Company, a
vessel plying between Evansville and
Cairo on the Ohio river, exploded three
of a battery of four boilers, completely
wrecking the vessel and killing and in-
juring more than twenty people.
The steamer left Evansville on the
afternoon of the fatal day, and between
ten and eleven oclock P.M., made a
landing at Shawneetown, several miles
below the confluence of the Wabash and
Ohio rivers : about one hour before mid-
night, the boat rounded out from this
port and pursued her course down the
Ohio. When within a distance of two
and a half to three miles from Shawnee-
town, the steamer was hailed to come
alongside by the Arkansas Belle, a vessel
of the same line lying to at Coles, a
landing said to be three to three and a
quarter miles below Shawneetown.
The Cleburne steamed down to the
Arkansas Belle, rounded in and drew up
alongside. When she came abreast of
the Belle, and about six feet separated
therefrom, the port and two central
boilers exploded with terrible violence,
killing among others the master and
chief engineer.
From the surviving officers of the
wrecked steamer, and the officers of the
Arkansas Belle, the following facts are
obtained : The Cleburne was running
with a pressure of one hundred and
twenty-five pounds steam (considerably
less than the U. S. certificate of inspec-
tion allowed) and blowing through the
feed water heater at time of explosion —
the furnace doors were opened to shorten
the fires— the doctor (feed pump) was
working at usual speed — the engines
were stopped or slowed whilst rounding
in. When the boats were nearly abreast
the port engine bell rang to go ahead —
the chief engineer who had previously
hailed the officers of the Arkansas Belle
from the engine room window, stepped
back on the foot board — dropped the
rods — opened the throttle, and the ex-
plosion promptly followed. The star-
board boiler was uninjured except the
breakage of connections, but after the
explosion it was found rotated fore and
aft on its seat. This boiler was shortened
after the explosion, and set up on the
steamer Idlewild for port duty. About
fifteen months after the explosion oc-
curred, the facts above were given to
the writer, with instructions from the
steamboat company to investigate the
explosion and report upon the probable
cause. No effort was spared by the offi-
cers of the company to arrive at the facts,
and every facility was offered to make
the inquiry as searching as the limited
materials permitted.
According to the certificate of inspec-
tion, the machinery of the Pat Cleburne
consisted of two non-condensing engines
each 20//x84// cylinder; steam was con-
veyed to these through b" copper pipes;
the doctor drove two cold water pumps
and two hot water pumps, each b" diam.
Xl2* stroke. The boilers, four in num-
ber, were of the return flue variety, each
24' long 37" diam. with 2—14* flues, the
clear space between flues, and between
flues and shell was 3". The shell courses
were of -£%" iron and the flues of J* iron.
All shell joints were single riveted. The
after ends of the boiler were concave,
and the mean length of flues about 22'
EXPLOSION OF A WESTERN RIVER STEAMER.
207
6*. Three boilers were furnished with
free safety valves, and one boiler with a
lock-up valve; each boiler had three
Mississippi gauge cocks and a low water
gauge; fusible plugs were inserted in the
fire courses and after ends of flues of
each boiler. The evaporation was col-
lected in a large cylindrical steam drum
lying athwartships and connected by 12"
legs to the second after course of boilers.
The steam pipes, (two), connected with
the steam drum, midway between the
first and second legs and the third and
fourth legs. Under the boilers, and di-
rectly opposite to the steam drum, lay
the mud drum; this was connected to
the boilers by 12" legs. The hot water
pumps delivered the feed through direct
copper pipes to the mud drum.
The boilers were built in Cincinnati
during the year 1870, and at time of ex-
plosion had been in use less than six
years. According to the U. S. inspector's
certificate, issued about five months pre-
vious to the disaster, the limit of work-
ing pressure was fixed at one hundred
and forty pounds by gauge, and every
detail of boilers and attachments com-
plied with the U. S. Treasury regula-
tions.
The exploded boilers were literally
torn to fragments, and no portions of
shells or flues were in existence at time
the writer began the investigation. The
fusible metal in the safety plugs was
Banca tin, and when found, nearly all of
these were melted out; but as the wreck
burned to the water's edge, within a very
few minutes after the explosion, the
probability is that these plugs were
melted out after, and not before, the ex-
plosion.
The officers in charge of the Pat
Cleburne, were of the best on the lower
Ohio, and the chief engineer was re-
puted without a superior in the manage-
ment of steam boat machinery. After
commencing the investigation, the fol-
lowing facts were obtained : from the
master of the wharf boat at Shawnee-
town ; that he was on the vessel, con-
versed with the engineer, and saw him
test the water level in the boilers within
fifteen minutes of the explosion: from
♦the second engineer of the Cleburne who
was asleep in the "Texas" when the
boilers let go; that he was on the boiler
deck within an hour of the explosion,
and no known derangement of doctor or
boilers existed, except a slight leak in
the second or third roundabout joint
upon the side of one of the central
boilers : from the master of the Arkansas
: Belle, who was on the starboard guard
I of his vessel when the Cleburne rounded
!in; that the port wheel of the wrecked
S steamer made a revolution or partial
j revolution before the boilers let go; in-
: dicating that the cam rods had been
dropped in gear, and the throttle opened
i to give steam to port engine; and that
the piston had begun its stroke. By way
of explanation it should be remarked;
that when a river steamer is under way,
and a necessity for stopping occurs, the
throttle valve is but partially closed, the
cam rods unhooked, and the valves set
to blow through.
Thus the surplus steam, instead of
wasting through the safety valves, is
blown through the cylinder into the
; heater, and utilized to elevate the tem-
perature of the feed water to the boilers.
The facts enumerated, from the sur-
viving officers of the wrecked steamer,
the officers of the Arkansas Belle, the
| superintendent of the steamboat com-
pany, and the inspection certificate, were
I the basis of examination. In the West,
and, so far as the writer is aware, in the
East also, when a steam boiler explosion
occurs, the first step is to secure a scape
goat to carry the burden of blame : if the
engineer in charge survives the disaster,
he is usually " honored " with the ap-
; pointment ; if he is killed, sympathy
overbalances public prejudice, and the
excoriation is discharged in some other
direction.
In the case of the Cleburne, however,
I the very excellent discipline maintained
! by the steamboat company, together
with the known qualifications of the
officers of the steamer, and especially
j the fact that the unfortunate chief engi-
neer was above suspicion of incapacity
or negligence, had an effect to stultify
wild speculation on the cause of the ex-
plosion.
The facts obtained support the follow-
ing assumptions :
First. No known defect existed in the
! boilers or feed water machinery of the
j Cleburne when she rounded out from
j Shawneetown.
Second. Upon leaving Shawneetown,
208
VAN NOSTRANIXS ENGINEERING MAGAZINE.
the Cleburne steamed up to the usual
running pressure; and the signal to come
alongside the Arkansas Belle was unex-
pected : (shortening fires and blowing
off were resorted to, to control within
safe limits, the steam pressure).
Third. No evidence of danger on the
Cleburne had presented before coming
alongside the Arkansas Belle : (the fire-
men having opened the furnace doors
and walked out on the port guards,
and when nearly abreast, the chief engi-
neer of the Cleburne came to the engine
room window and cheerily hailed the
officers of the Belle).
Was low water the cause of the explo-
sion ? When the Cleburne left Shawnee-
town, we are informed, the usual level of
water obtained in all the boilers; from
this port to the meeting with the Arkan-
sas Belle, not more than fifteen minutes
elapsed, during which time no steam
was blown off save through the engines.
Neglecting the leak, which we are in-
formed was insignificant, then the reduc-
tion of water level in the boilers (assum-
ing a total failure upon the part of the
feed pumps to supply during the interval)
would be that due to evaporation alone.
The aggregate heating surface to each
boiler is taken as 325 superficial feet, and
maximum evaporation per hour per
square foot of heating surface as six
pounds ; and maximum evaporation per
325 X 6
boiler for fifteen minutes =487.5
pounds, or 8.75 cubic feet at temperature
of 353 Fahr. This evaporation corre-
sponds to a reduction of water level of
less than one and one half inches; the
usual level of water over the flues was
four to five inches. All evidence went
to prove that no failure to* supply the
boilers occurred prior to the explosion;
the doctor was simply a small beam en-
gine, with a plain slide valve; driving
four pumps — two piston pumps for cold
water, and two plunger pumps for hot
water. The cold and hot water pumps
were in duplicate; in the event of failure
of one pump, the other was of, sufficient
capacity to supply the boilers. As
against a sensible reduction of water
level in the boilers during the fifteen
minutes run — whether from failure of
the "doctor" to supply, or from any
other cause — the frequent examination of
the water level is " second nature " to the
experienced engineers; hence the writer
is unwilling to believe that a person of
the experience *and known capacity of
the first engineer of the Cleburne, with
the doctor and water gauges directly
under his eye, would fail to detect a
fault in the working of the one, or test
the other, during the run from Shawnee-
town to the meeting with the Arkansas
Belle. Assuming, however, that no
water was supplied to the boilers after
leaving Shawneetown, then the reduction
of water level, by evaporation alone,,
could not have been sufficient to uncover
the flues. In fact, the water over the
flues at the time of explosion could not
have been less than two and a half to
three inches, quite enough for all pur-
poses of safety. The blow off, or mud
valves, as they are termed on the Western
rivers, closed under pressure, and could
have been opened only by manual
effort; no evidence offered to show that
these valves either leaked or were open-
ed, hence it is reasonable to conclude that
no water left the boilers by this outlet.
The leak, already noted in one of the
central boilers, was in a roundabout
seam forward of the bridge wall, and
had been noted from time to time by
the chief engineer for several days.
From the statements of the colored fire-
men who survived the disaster, this leak
was due to defective caulking of the
overlap, and was no evidence of weakness
in the boiler. (Boilers frequently leak
at the riveted joints, and a new boiler
absolutely free from seam leaks is a rare
circumstance. But a leaking joint in an
otherwise sound boiler, is no cause for
alarm; the caulking that makes a joint
tight under pressure adds nothing to the
pronounced strength of a boiler, and the
only effect of a seam leak would be to
impair the economy of performance, and
impose an increased duty on the feed
pump). This leak was in plain view
from the front of the boilers, and could
be seen by the fireman every time the
furnace doors were opened; these were
opened and fires banked within two to
three minutes of the time of explosion^
and it is not very probable that an in-
crease had taken place in the leak, with-
out the fireman observing it. The after
end of each flue contained a fusible plug,
and at this point the hot gas passing
forward through the flue is at the maxi-
EXPLOSION OF A WESTERN RIVER STEAMER.
209
mum temperature; the plugs were in-
serted in the crowns of the flues, where
the collection of scale is a slow process;
and it is very unlikely that of eight in-
dependent plugs supposed to be in the
same horizontal plane, not one would
have melted and given an alarm, had
the water level fallen below the crowns
of the flues before the explosion.
When found, the fusible metal in some
of these plugs was melted out, but the
fragments of the boilers lay on the wreck
of the vessel while it burned; and there
can be no doubt that these plugs were
fused in the raging Are which promptly
followed the explosion.
When the boilers of the Cleburne
ruptured the fusible plugs were intact ;
for the peculiar whistling sound, as the
steam and water rushes through the
orifice in the plug, could not have escap-
ed the attention of the engineers and
firemen on watch. Let it be supposed,
however, that the water level had fallen
so low as to uncover the crowns of the
flues and melt the metal in the plugs (as
it has been asserted in connection with
this disaster) ; would this have been a
sufficient cause for the explosion ? Evi-
dently not, if fusible plugs are possessed
of any virtue : for the plug, or rather the
core of the plug, is not supposed to melt
until the crown of the flue is uncovered,
and heated to a temperature of 420°
Fahr.; and as the fusing and blowing
out of the core is only intended as a
timely warning against danger, it follows
that the melting of these plugs would be
no argument in behalf of low water as
the cause of the explosion. As a further
argument against low water as the cause
of the explosion on the Cleburne : in
rounding in the vessel listed to port,
thus elevating the boilers to starboard,
and low water, if it obtained at all, ob-
tained to the greatest extent in the star-
board boiler; this boiler icas wholly un-
injured, and is now in daily use on an-
other vessel of the same line.
Without discussing " low water" as a
probable cause of explosion in boilers of
this class, set and fired as were these
boilers; the writer would suggest that
low water was not the cause of explosion
in this instance, and all the facts appear
to sustain this view.
Examining as to the probability of ex-
plosion by defects of materials, improper
Vol. XIX.— No. 3—14
construction or deterioration from use;
we find that the boilers (four in number)
were all made at the same time, of the
same brands of iron, of precisely the
same dimensions, and had been worked
together for six years, under like con-
ditions. During this time they had been
inspected many times, at different ports,
by different inspectors, and had defects
of materials existed, they would have, in
all probability, been detected before the
explosion. Whilst there is no doubt of
the reckless manner in which boilers are
put together being a fruitful source of
explosions, no evidence was offered to
show that the boilers of the Cleburne
were not well built; and if the surviving
boiler is an index of the workmanship,
they were in this respect considerably
above the average. The precise con-
dition of the boilers at time of explosion
is not known, except they had been care-
fully washed out a few days before.
But as the boilers had always worked to-
gether, and resisted the same strains,
and destructive action of fire and water,
it is reasonable to presume that the un-
exploded starboard boiler was no better
than the others. This boiler was opened
after the accident, and a careful exami-
nation revealed no special or dangerous
deterioration.
It has been suggested that over-press-
ure was the cause of the explosion. Un-
der the certificate of inspection the
boilers of the Cleburne were limited to
140 pounds by the gauge; but at the
time of the explosion, or more correctly
a few minutes before, the pressure was
125 pounds; the last inspection was
made less than five months prior to the
accident : and under the U. S. Treasury
regulations the working pressure is taken
at one-sixth the tensile strength of plates,
and the proof pressure at one and one-
half times the working pressure : hence,
the proof pressure of these boilers, ac-
cording to the inspector's certificate, was
210 pounds. It is scarcely possible that
their strength was diminished forty per
cent, during the last five months of use.
It might be supposed that the steam
guages were unreliable, and failed to in-
dicate the true pressure, which was con-
siderably higher than indicated by the
gauge. But from all the evidence fur-
nished the writer, the pressure that rup-
tured the boilers was less than that at
210
VAN NOSTRAND's ENGINEERING MAGAZINE.
which the safety valves were set to blow :
this was one hundred and forty pounds,
and the valves were frequently eased on
their seats to insure prompt action.
As the writer understands the term,
over-pressure was not the cause of the
explosion; that the strains at time of
rupture were in excess of the strength of
the boilers is evident; but that the steam
pressure steadily increased until the
strains were in excess of the resisting
powers of the boilers is scarcely possible,
in view of the testimony of the engineer's
assistant, and the surviving firemen, that
the pressure was, within two or three
minutes of the explosion, one hundred
and twenty five pounds, with furnace
doors open and fires banked.
Without adverting to other improba-
ble theories of explosion, as applied to
the ill-fated Cleburne, the writer will
endeavor to establish what, in his opin-
ion, was the cause, in accordance with
the facts related. When the steamer
left Shawneetown, the " regimen " of the
boiler was calculated for a long run.
The boiler capacity of river steamers to
reduce dead load is usually a minimum,
and active firing is frequently resorted
to, to maintain a running pressure. But
the flow of steam out of the boilers, and
the flow of water in, is usually cor-
respondingly uniform, and no evil effects
are liable to follow forced firing.
When the Cleburne was hailed by the
Arkansas Belle to come alongside, the
condition of fires and steam pressure
were unfavorable to a stop, and the
furnace doors were opened and fires
banked. But the time elapsing from
receiving the signal, to its coming along-
side the Bell, could not have been more
than four or five minutes; and the time
elapsing between the banking of fires
and the explosion not more than two or
three minutes. Upon reception of the
signal to stop, the engines of the
Cleburne were slowed; and whilst round-
ing in, the use of the wheels would be
irregular, and chiefly confined to the
port wheel; and when the vessels were
nearly abreast the port wheel was
stopped entirely for an interval of several
seconds, during which time the vessel
drove on by momentum. In warping in
a spurt from the port wheel was neces-
sary to avoid a bow collision — the port
engine was started — when the explosion
of the port and two central boilers
almost instantly followed. Previous to
the rupture of the boilers the steam and
water had been heated to a temperature
of 353° Fahr., and the iron of the under
courses and flues to a temperature some-
what in excess of this. The walls of the
furnaces were glowing from the active
firing and % the circulation sufficient to
prevent overheating of iron or water;
directly the speed of engines was slowed
the rapid ebullition in the boilers was
checked by the increase of pressure, and
whilst the flow of feed water into the
boiler may have been unchanged, the
flow of steam out of the boiler, for a
brief period of time ceased nearly, if not
quite altogether. The natural result of
this would be to reduce the circulation
from previous activity to a state of
partial quiescence, and localize the heat.
The capacity of the water to receive
heat and vaporize would be temporarily
diminished, and the iron of the under
courses quickly heated to a temperature
sufficient to repel the superincumbent
water from the plates. This tempera-
ture is variously estimated from 380° to
430° Fahr., hence we accept a mean of
405° as applicable to the iron in the
boilers of the Cleburne; then an addition
of 50° Fahr. would anticipate the condi-
tion of plates necessary to perfect repul-
sion. The previous active fires in the
furnaces; the unexpected stop; the brief
interval between receiving the signal to
stop, and coming alongside the Arkansas
Belle, were conditions favorable to the
repellant action. Without entering into
a discussion of the theory of repulsion,
the rationale of which is well under-
stood by steam engineers, the writer
would suggest that directly the repellant
action occurs, the iron of the boiler
instead of acting as a vehicle of trans-
mission of heat, becomes as it were a
receiver of heat, and the temperature
of the plates is rapidly augmented by
the impinging hot gas. It is assumed,
in the case of the Cleburne, that the
repellant action occurred at a time when
the engines were stopped, and the flow
of steam from the boiler at a minimum,
or checked entirely. At this time the
circulation was sluggish, and ebullition
slow and irregular. Meanwhile the
storing up of heat in the iron of the
shell went on until an unknown tempera-
THE HYDEOLOGY OF THE MISSISSIPPI RIVER.
211
ture was attained; no increase of pressure
was indicated by the gauge, and no
appreciable variation was noted in the
water level; the fires were banked and
furnace doors open, and so far as the
engineer could qualify, every precaution
had been taken to avoid danger. The
port engine bell was rung to "go
ahead"; the engineer dropped the cam
rods, opened the throttle, and the piston
began its stroke; the flow of steam to
the engine reduced the pressure in the
I steam drum and steam room of the
j boilers, sensible heat became latent with
a quick vaporization of a portion of the
water. The reduction of temperature of
i the water, and the return to the highly
! heated plates, were instantly followed
by the production of a comparatively
| large volume of steam which, in seeking
I to escape to the surface and vaporize,
carried the water with it and delivered
it as a projectile against the limiting
surfaces of the boilers.
THE HYDROLOGY OF THE MISSISSIPPI RIVER.
REVIEW OF REPORT BY HUMPHREYS AND ABBOT.
By JAMES B. EADS, C. E.
Written for Van Nostrand's Magazine.
As the report on the Mississippi river
made by Generals Humphreys and Abbot
in 1861, has been recently republished
by the Government, and as it contains
certain grave errors touching the naviga-
tion of the river and the reclamation of
its alluvial basin, I desire to expose
them, and to show that many of the
statements made by the authors of the
report are not sustained by the facts to
which they refer. If the reader will fol-
low me attentively, I promise to demon-
strate, to his entire satisfaction, the utter
absurdity of these statements.*
It does not interest the general .public
to know whether the quantity of sedi-
ment carried by the water of the river, is
adjusted by the rate of its current or not;
or whether the real bed on which rest its
moving sand bars, is of recent, or of an-
cient geologic stratification, or whether it
wears rapidly or slowly under the action
of its current, unless these questions are
known to have an important bearing
upon the commercial and agricultural
* In 1874 I proved to the satisfaction of the Congress of
the United States, by the data contained in this report, that
the theory of har formation at the mouth of the Missis-
sippi advanced by its authors, was totally wrong, and thus
secured for the river an unobstructed and open outlet
to the sea through the bar at South pass. It is needless to
say that the predictions made by General Humphreys re-
garding the re-formation of the bar in advance of the
jetties, have not been realized. This paper is intended to
expose other erroneous theories advanced iu the same re-
port, and which stand in the way of a correct system of
improvement of the entire river, and which are declared
to be conclusively demonstrated by patient scientific and
experimental investigation.
prosperity of the Valley of the Missis-
sippi. When this is known to be the fact,
the scientific interest in them is com-
pletely dwarfed by the overwhelming
practical bearing which they have upon
great national interests. It is for this
reason that I select your widely circula-
ted journal as the surest means of
thoroughly reaching the intelligent
readers of the country, rather than to
attempt, through the less extensively
circulated records of any of the scien-
tific bodies of which I am a member, an
exposition of the dangerous errors ad-
vanced by Humphreys and Abbot.
THE RELATION BETWEEN THE CURRENT
AND THE SUSPENDED SEDIMENT.
In 1874, I stated in a pamphlet, that
the chief portion of the sediment dis-
charged by the river into the Gulf is
carried in suspension, and " that the
amount of this matter, and the size and
weight of the particles which the stream
is enabled to hold up and carry forward,
depend wholly upon the rapidity of the
stream, modified, however, by its depth."
General Humphreys immediately
afterwards said,* this statement is "in
direct conflict with the results of long
continued measurements made upon the
quantity of earthy matter held in sus-
* See Executive Document 220, 43rd Congress. Also
last edition of Report on the Mississippi River, page 674
212
VAN NOSTRAND'S ENGINEERING MAGAZINE.
pension by the Mississippi river at
Carrollton (near New Orleans), and at
Columbus (twenty miles below the mouth
of the Ohio), one of the chief objects of
which was to determine this very ques-
tion, whether any relation existed be-
tween the velocity and quantity of
earthy matter held in suspension. These
results prove that the greatest velocity
does not correspond to the greatest quan-
tity of earthy matter held in suspension;
on the contrary, at the time of the
greatest velocity of current at Carroll-
ton, the river held in suspension but
little more sediment per cubic foot than
when the velocity was least."*
These results when correctly inter-
preted prove precisely the contrary of
the idea here conveyed by General
Humphreys. He says that my state-
ment is in direct conflict with them,
and then proceeds in effect to tell
us, that there is no relation between
the velocity of the current and the sedi-
ment carried in a cubic foot of water,
which is a very different thing, as the
reader will soon see.
Gen'l Humphreys evidently means to
convey the idea that the most rapid cur-
rent carries but little more sediment
than the least, when in fact by his own
tables, it carried more than twenty times
as much as the least current at Carroll-
ton, and more than forty times as much
at Columbus.
They use the terms " a cubic foot of
water" and "the current," as expres-
sions having one and the same meaning;
whereas the current per second repre-
sents the force due not to one only, but
to an immense number of cubic feet of
water passing, in each second of time, by
the place where the current is measured;
and it is the total sediment suspended in
this immense number of cubic feet that
should be compared with the rate of the
current per second.
One of the chief objects, we are told,
was to determine " whether any relation
existed between the velocity and the
quantity of earthy matter held in sus-
pension." In what ? In a cubic foot
of water, or in the whole river ? Cer-
tainly in the latter, for the quantity, in a
cubic foot is of no practical value except
* See last edition Mississippi Kiver Report, page 138,
and Appendix D.
as a means to determine its relation to
the whole quantity.
They pushed their investigations how-
ever only to the extent of trying to find
the relation between the current per
second and the sediment in a cubic foot.
Failing to discover this, for they pro-
ceeded no farther, and supposing that
they had solved a problem in which they
had neglected two essential elements,
they announced their astonishing dis-
covery that no relation whatever exists
between the rate of current and the
quantity of sediment suspended by it;
or, in plainer English, between cause and
effect.
This question could only be solved by
bringing the elements of space and time
into the computation for the sediment,
just as they are brought into the current
measurement, that is, by comparing the
mean velocity per second with the total
weight of sediment suspended per
second. They, however, compared the
mean velocity in every instance with the
mean sediment contained in but a single
unit of the river's volume, and they not
only published the results of this mean-
ingless comparison, as a proof that there
is no relation between the' rate of cur-
rent and the quantity of sediment, but
they have founded unsound theories
upon this error, and have officially
advised a dangerous system of river
treatment based upon it.
I will now show why they should have
compared the current, per second, with
the total quantity of sediment passing
by their point of observation in the same
unit of time. To make this easily un-
derstood by the general public, compels
me to state much that will be common-
place to the scientific reader.
Motion cannot occur in matter without
an expenditure of force. The transport-
ation of sedimentary matter in water,
can, therefore, only result from an ex-
penditure of force, and only by supply-
ing the requisite amount of force, as it
becomes exhausted, can these matters be
lifted up and kept from falling back to
the river bottom. Being heavier than
water, it is just as impossible to uphold
them in it without force, as it is to raise
chaff in the air, or sand and dust in a
whirlwind without it, The current
caused by the river flowing from a higher
to a lower level supplies this force.
THE HYDEOLOGY OF THE MISSISSIPPI EIVEE.
213
The investigation of all questions relat-
ing to the expenditure of force, belongs to
that branch of science called Dynamics,
and in all such problems, whether they
relate to a treadmill, or a steam engine;
to the tiniest ripple, or the grandest
river ; to a grain of sand as it moves on-
ward to the sea, or to the most majestic
planet that pursues its pathway in the
heavens, each and all involve the con-
sideration of four distinct elements in
their solution; and unless each one of
these be duly considered no assumed
solution of the question can be worth
the paper on which it is made, except
perhaps to " point a moral."
These elements are, first, force, second,
matter, third, space, and fourth, time.
Gravity and pressure are examples of the
first element, and one of these, gravity,
constitutes the first factor in our prob-
lem. The term volume, or mass, is used
to indicate the quantity of the second
element, while the term speed or velocity
embraces the last two elements, and in-
dicates the space through which the force
acts, and the time involved in the action.
The amount of force expended can
only be ascertained by knowing the
weight or pressure exerted,' the space
through which it acts, and the time oc-
cupied in such action.
The relation of these four elements to
each other may be illustrated by sus-
pending two equal weights from the ends
of a lever with equal arms, supported at
its middle. While at rest they present
simply a statical problem, in which force,
matter and space alone, are involved.
When in motion, however, the other ele-
ment, time, necessarily enters into the
problem. If motion be imparted to the
weights, and one sinks towards the earth,
the other will be raised through a space
exactly equal to that through which the
other falls, and in the same time in which
the other falls. The velocity and mass
of the descending weight gives the meas-
ure of the force expended. This force |
can only be determined by these
three elements, first, the weight, second,
the space through which it moves, and,
third, the time required to move through
the space. The work clone consists in its
raising the other weight through the
same space, and in the same time. There-
fore the force expended will be precisely
the same that is required to raise the !
same weight, through the same space, in
the same time. Hence it is an axiom
that " The work done must bear an in-
variable quantitative relation to the
amount of force expended." *
If the point of support of the lever be
moved from the center toward one
weight until the latter will balance one
only half as heavy, it will then be found
that when the large weight descends in
one unit of time through a certain space,
the small weight will have been raised
through twice that space in the same
unit of time, and therefore, the small
one will have moved with twice the
velocity. Hence, if we raise a weight
through twice the space, in the same
time, we must either double the force, or
lift but one-half the weight. If we re-
verse the motion of the weights, and the
smaller one descends, we illustrate the
fact that by doubling the velocity, half
the force will lift twice the weight.
In the steam engine the pressure of
the steam takes the place of the pressure
or force exerted by gravity. To determ-
ine the power of the engine we must
have, first, the pressure upon the piston,
second, the space through which it moves,
and third, the time occupied in its move-
ment. If the same pressure be main-
tained per square inch in each of two
cylinders, and the velocity of the piston
in one be twice as great as in the other,
the more rapid one will develop as much
power as the other with half the area of
piston ; just as half the weight on the
doubled length of the lever arm can de-
velop the same amount of force as the
whole weight, because it will then move
with twice the velocity.
The power of a waterfall is estimated
by the same three elements. The weight
of the water falling in one minute of
time and the number of feet of space
through which it falls in the time, are
multiplied together, and when divided
by 33,000 foot pounds, the quotient will
represent the horse power of the water-
fall or head of water; a horse being sup-
posed to be able to raise 33,000 pounds,
one foot high, in a minute of time.
It is unnecessary to point out by far-
ther illustration the fact that these three
elements, matter, space, and time, are
inseparably related in any investigation
to determine either the amount of force
* Mayer.
214
van nostrand's engineering magazine.
expended or of work done. I need only
add that no matter how intricate the
machinery, or secret the medium through
which moving bodies transmit their
forces, these three elements are as abso-
lutely requisite to determine the amount
of the force expended, or the work done,
as the depth, width, and length of a
rectangular box are, to determine its
capacity ; and no matter how occult may
be the relation between them, it is never-
theless as indissoluble, complete and per-
fect as in this simple illustration.
The work performed is precisely equal
to the force expended when operating
any steam, water or other motor, but the
work practically considered is of two
kinds: one of which may be called profit-
able or visible work, and the other un-
profitable or invisible work, the latter
being that part of the force which is
expended in overcoming friction, back
pressure, atmospheric resistance, radia-
tion, &c.
The work done by the force which the
Mississippi River expends we may, for
the sake of illustration, also divide into
two kinds, and call the first, invisible, or
unprofitable work, among which we may
class the overcoming of the friction of
the bed of the stream, the friction among
the particles of water, the resistance due
to the irregularities and bends in the
channel, the atmosphere, &c, leaving
to be considered, as the visible or pro-
fitable work, the transportation of its
immense burden of sediment. The prob-
lem we are considering and which these
gentlemen claim to have determined, is
the relation which the current, or force,
expended by the river bears to this great
burden of earthy matter.
Let us suppose a railway train be used
in transporting grain, and that we wish
to determine the relation between the
force (or coal) expended, and the quan-
tity of grain carried ; we would carefully
ascertain the total coal burned in some
definite time, for instance, in one hour,
and also the total weight of the grain car-
ried in that hour, and likewise the space
over which it was carried during that
hour. We would then be able, by com-
paring the total coal with the total weight,
to declare absolutely that so much coal
or force expended, was equal to the car-
rying of so much grain a certain distance
in one hour, and the relation between the
force expended and the work done would
be so expressed.
In such investigation we would have
1st, force (the coal) ; 2d, matter (the load
of grain); 3d, space (the distance the
load is carried) ; and 4th, time (the hour
during which it was carried). By repeat-
the measurements under similar condi-
tions, but with different quantities of
time, space and weight, this relation be-
tween force and work would appear con-
stant and inseparable. An instructive
comparison could only be made, either
between the totals of the force and work,
or between their respective units, and in
either case time and space would be in-
dispensable elements to be considered.
But if the total coal be only compared
with the weight of a single bushel of the
grain, and no note be taken of the space
through which it was carried, nor of the
total number of other bushels that were
carried in the same time, the comparison
would have no significance whatever. A
diagram to represent such a comparison,
as an ultimate solution of the question,
would not only be meaningless but ab-
surd ; yet it would be precisely similar in
principle to the diagrams which Hum-
phreys and Abbot represent on plates
XII and XIII of their report, where the
current per second is contrasted with the
sediment found in a single cubic foot of
water. An accurate fac simile of plate
XIII is herewith shown. (See diagram
No. 1.)
If the mean current at Columbus was six
feet per second, an entire section of the
river six feet long must have moved at
that place and time through the space of
six feet, and the force expended was,
therefore, the entire force due to the
motion of this whole section during that
second.
The mean current given in feet per
second, is, therefore, an exponent of this
whole force, and if it be six feet per
second, it can only be intelligently com-
pared with the total sediment carried in
an entire section of the river six feet
long, and not with that in a single cubic
foot. If we multiply the cross section
of the river in square feet by the current
in lineal feet per second, the product
would be the number of cubic feet in the
section, and these multiplied by the num-
ber of grains of sediment in one foot,
THE
HYDROLOGY OF THE
MISSISSIPPI
RIVER.
215
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would give the proper amount* for com-
parison with the current.
As the work done and the force ex-
pended must be precisely equal, it is
evident that the three elements, namely,
matter, space and time, are as necessary
to determine the amount of work done,
as they are to determine the amount of
force expended.
In appendix D of their report will be
found tables, giving in cubic feet, the
daily volume of water flowing per
second, by the velocity base or point
where these measurements were made:
These quantities were ascertained by
multiplying the cross section of the
stream in square feet each day with the
mean velocity of the current at the time,
in linear feet per second. The two
absent dynamic elements, namely, time,
(one second), and space, (the linear feet
the river moved in one second), are thus
included in these tables. By taking the
average or mean weekly discharge in
these tables, and multiplying it with the
mean sediment in grains found each
week in one cubic foot of water, given in
the tables, we get the proper quantities
of sediment to compare with the average
rate of current per second.
Diagram No. 2 is prepared in this man-
ner from precisely the same data which
Humphrey's and Abbot used to prepare
Diagram No. 1, except that in mine the
absent elements, space and time, have
been included as above explained. A
216
van nostrand's engineering magazine.
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I
THE HYDROLOGY OF THE MISSISSIPPI RIVER.
217
third line is shown on my diagram which
gives the mean weekly volume of dis-
charge, by which the total weekly mean
of sediment was ascertained.
If the relation between the current
velocity and the quantity of sediment
does not exist, as Humphreys and Ab-
bot assure us, no correspondence or
synchronism could be graphically shown
between them on diagram No. 2 by any
possible scientific analysis to which these
data can be subjected. By their dia-
grams, none whatever is shown, because
of their error.
An inspection of diagram No. 2 proves
the existence of this relation in a way
that admits of no dispute, and shows
how remarkably sensitive the sediment
is to any change of velocity in the cur-
rent. This is particularly noticeable at
each period when the current began to
decline. The river rose and fell six times
at Columbus while the observations were
being made. These periods are indi-
cated by the letters A, C, E, F, G, and
H. The loss in velocity at each of
these six periods, during the eight
months, is invariably and immediately
marked by a corresponding reduc-
tion in the quantity of sediment. No
one can look at these two diagrams,
made from the same tables and to
determine the same question, without
feeling assured that
" Some one has blundered."
A diagram made in the same manner
from the Carrollton observations will
show an equally striking evidence of the
intimate relation between the rate of cur-
rent and the quantity of . sediment,
which has been so persistently and dog-
matically disputed.
The error made by Humphreys and
Abbot when investigating the results of
their experiments at Columbus and Car-
rollton, consists in supposing they were
comparing a definite . exponent of the
force with a corresponding exponent of
the work, when, in fact, the elements of
space and time were wholly absent in the
exponent of the work ; and not only
were these neglected, but only one single
unit of the third element of the work was
taken as the corresponding exponent to
compare with the force.
Suppose we should attempt to show
the relation between a certain quantity
of grain, and the capacity of a rectan-
gular box which it had exactly filled.
Having ascertained the number of cubic
inches of the grain, what relation could
we hope to show between this quantity
and the capacity of the box, if we com-
pared it with only one single inch of the
length of its bottom ? Not only would
we be ignoring the total length of the
box, but we would also be neglecting the
two other factors of the problem, name-
ly, its width and its depth, and the com-
parison, therefore, would be utterly un-
intelligible. Such a mistake would be
inexcusable in one who had barely
entered on the threshold of geometry.
The mistake made by Humphreys and
Abbot is similar to this, and it is one
equally unpardonable even in the merest
tyro in the science of dynamics. Yet,
relying solely upon this method of inves-
tigation, the Chief, of Engineers of the
United States army, to defeat the adop-
tion of the present system of improve-
ment at the mouth of the Mississippi
river, actually prepared a letter which
was read in the House of Representa-
tives in 1874, and which referred to the
subject we are discussing in the follow-
ing language : " It is probably unneces-
sary for me to say here that, the state-
ments which Mr. Eads has made in the
pamphlets he has published concerning
the conditions existing in the Mississippi
river and at its mouth are the mere re-
vival of old assumptions, which experi-
mental investigation has long since
shown to be utterly unfounded in
fact."
Having clearly explained how their
defective knowledge of the principles of
dynamics led them astray, and having
proved by their own testimony that they
are clearly in error, let us now see to
what absurd conclusions their unfortu-
nate mistake carried them.
Referring to their experiments at Co-
lumbus and Carrollton they say on page
135: "An inspection of the preceding
table must convince any one that the
Mississippi water is undercharged with
sediment, even in the low- water stage.
A most important practical deduction
may be drawn from this fact, namely the
error of the popular idea that a slight
artificial retardation of the current, that
caused by a crevasse for instance, must
produce a deposit in the channel of the
river below it."
218
VAN NOSTRAND'S ENGINEERING MAGAZINE.
On page 417 this undercharged theory
is repeated, as follows :
"A glance at the two diagrams is suf-
ficient to demonstrate the falsity of the
assumption, that Mississippi water is
always charged with sediment to the
maximum capacity allowed by its vel-
ocity."
Having exploded the " error of the
popular idea " that cause and effect are
related, we need not be surprised at this
undercharged theory. And although we
may have supposed that matter cannot
move independently of law, and that nei-
ther an atom nor an avalanche can stir ex-
cept in strict obedience to ordinances more
fixed than those which swayed the Medes
and Persians, we must be prepared to
believe that the sediment of the Missis-
sippi is an exception to this rule, for,
having proved conclusively that its
water is always undercharged, we are
gravely assured on page 135, "If the
water be undercharged, the distribution
of sediment will follow no law, the
amount at any point being fixed by the
accidental circumstances of whirls, boils,
&c." With such astonishing declara-
tions as these, the reader will be partial-
ly prepared for the no less wonderful
announcement that as the sediment will
follow no law, the feeblest current can
carry just as much of it as the most
rapid current.
This statement will be found on page
684 of the last edition. It is as follows:
" In fine, these measurements upon
the quantity of earthy matter, suspend-
ed in the Mississippi river, show that at
no time has the water been so heavily
charged with it that the current could
not carry it along in suspension to the
same extent as it did when the quantity
of earthy matter was least; and they
further show that the current of the
Mississippi river, when most feeble, can
carry in suspension the greatest quantity
of suspended earthy matter found in it,
to the same extent that it can carry the
least quantity found in it."
I know of but one other statement
concerning the wonders of this river
that can compare with this one.
In the last eighty years several cut-
offs have occurred below the mouth of
the Ohio, by which the channel was
shortened about seventy miles. Based
»upon this fact, a distinguished writer has
published the startling prediction that
within a few centuries, two cities on the
river, (Cairo and New Orleans) although
now distant from each other one thou-
sand miles, must, by this shortening
process, inevitably be drawn together!
By an inverse method of reasoning on
these facts, he arrives at the interesting
conclusion, that in some remote geologic
period the Mississippi extended to
Cuba ! *
When pursuing a different line of in-
vestigation, distinguished engineers ar-
rive at the equally astonishing conclu-
sion, that the current of the Mississippi
when most feeble can carry as much
sediment as it can when most rapid, we
may from the standpoint of common
sense, safely assume that while the
deductions, in each case, rest upon
facts, the conclusions in both were ar-
rived at by defective methods of scienti-
fic investigation.
If we examine these Carrollton and
Columbus experiments we do not find
this surprising statement about the
power of feeble currents verified.
In the quotation, I have italicised the
words " the current," to attract attention
to the fact that no distinction is made
between what the current carried and
what a cubic foot of water carried.
Diagram No. 2 shows what the current
carried, while diagram No. 1 shows
what was carried in a cubic foot. The
one emphatically disproves this absurd
statement, while the other furnishes no
ground whatever for making it, because
it conveys no idea at all of the relation
between the current and the sediment.
At Columbus, the most feeble current
carried but ten million grains of sedi-
ment per second, while during the third
week in April, when the current was
about four times as rapid, it carried 480
million grains, or forty -eight times as
much as " when the current was most
feeble." At Carrollton the current was
most feeble in November, being but
little more than a foot and a half per
second, and then it carried less than 22
million grains, while in June, when the
current was nearly three times as rapid,
it carried 500 million grains, or nearly
twenty-three times as much as when it
was most feeble !
Dr. C Hagen, Director General of
* Mark Twain.
THE HYDROLOGY OF THE MISSISSIPPI RIVER.
219
Public Works in Prussia, and one of the
most eminent engineers in Europe, in a
recent criticism upon Humphreys and
Abbot's theory regarding the distribution
of velocity in flowing water, says :
"The young student of hydraulics is
sometimes compelled to accept certain
theorems as true and proven which, to
say the least, are still doubtful; but he
has as yet never been expected to receive
devoutly a demonstration like this, and*
to regard it as a progress of science."
This comment seems peculiarly applica-
ble, likewise, to their conclusions regard-
ing the relation between the current and
the suspended sediment."
On the same page of their report from
which the preceding remarkable extract
is taken, is the following:
"This proposition, therefore, respecting
certain velocities of current always car-
rying certain fixed quantities of earthy
matter, and always adjusting those quan-
tities according to its own variations of
strength, is so entirely disapproved by
facts that it will not be considered
again."
In view of the fact that their own
tables prove the utter fallacy of this
statement, it is amusing to see the satis-
faction with which it seems to be ut-
tered.
It will be observed that all of these
mistaken conclusions rest upon the as-
sumption that the sediment found in a
cubic foot of water, moving at different
velocities, was a correct exponent of the
ratio between the speed of the river and
the burden it carried.
After referring to plates XII and XIII
to prove that " the river is never charged
to its maximum capacity of suspension "
they declare (page 417) — "Hence if
enough water had been taken from the
•river at the date of those floods (1851
and 1858) to reduce its velocity nearly to
that of the lowest stage, no deposit in its
channel could have occurred."
The highest velocity at Carrollt©n was
6.16 feet per second, and the sediment
was then only 252 grains per cubic foot.
In September the current had declined
to 2.44 feet per second, while the sedi-
ment was 268 grains per cubic foot.
These quantities were doubtless in view
when the above declaration was made,
because, as far as their "experimental
investigation " had advanced it showed
j that a current less than 2 J feet per sec-
| ond actually carried more sediment per
j cubic foot than a current of over 6 feet
! per second. But the high current carried
I 280 million grains per second, because
1,140,000 cubic feet of water were then
passing per second, while the low current
carried but 100 million grains per second,
| or but little more than one-third as much;
I because the volume of water was then
' only 375,000 cubic feet per second.
At Columbus, 320 grains per cubic
j foot were carried with the highest cur-
i rent, 8^ feet per second, in June, while
| 608 grains were carried in August with
j a current of 2.57 feet per second.
But when we bring in the absent dy-
! namic elements of space and time, and
! ascertain by them the total quantity of
work really done by the current at
Columbus, we find that the river carried
\ 444 million grains per second with the
| high current, and only 180 millions with
the low current, because its volume of
discharge with the high current was
nearly 1,400,000 cubic feet per second,
and only 280,000 with the low current.
Hence it is simply impossible that the
high water burden can be carried with
the low rate of velocity without* deposi-
tion occurring.
We learn from the illustration of the
lever and weights, that the same force
i can only raise half the weight if it raise
it to double the height in the same time.
Hence we should not expect to find as
much sediment per cubic foot in deep
water, with a given velocity, as in shoal
water. This fact will account for the
quantity being greater per cubic foot
\ in some of the measurements when the
current was moderate, than when it was
most rapid. The greater distance be-
tween the sediment and velocity lines
i during the first four months on diagram
| No. 2 is very marked. These were the
high water months and the modifying
effect of the depth of the stream on its
power to suspend the sediment is clearly
shown by the greater distance between
these lines.
The depths as well as the velocities
I are usually greatest during floods. When
! the current was 8.25 feet per second, the
depth at Columbus was 27 feet greater
than when it was 2,57 feet per second,
yet the tables show that the low current
supported a greater quantity per cubic
220
van nostrand's engineering magazine.
foot than the higher velocity, because,
first, it did not raise it so high above the
bottom; and, second, because the river
was falling. As many hours are neces-
sary, even in still water, for all the sedi-
ment to fall, it must be evident that
when the river is falling and the current
diminishing, the water will have a greater
amount in suspension than is then due to
the velocity; and that when it is rising
and the current increasing, it will then
have less in suspension than the velocity
would indicate. Therefore, the quantity
found at a low velocity, it* the river be
falling rapidly, may be much greater per
cubic foot of water, not only because of
less depth, but also because of a dimin-
ishing velocity. The diagram (No. 2)
shows that both causes operated to in-
duce this great charge of 608 grains per
cubic foot with this low rate of current.
The tables of sediment show also that
the lower part of the water is somewhat
more largely charged with sediment than
the upper. This would act as an addi-
tional cause for the low water currents
showing a larger ratio of sediment, par-
ticularly when the river has been falling
some time. When it first begins to lose
its high velocity, the largest particles,
such as gravel, (which is undoubtedly
carried in suspension with the high-
er velocities, in moderate depths) and
coarse sand are first deposited. These
fall rapidly, while the smaller particles
require more time for settlement, accord-
ing to their magnitudes and specific
gravities. Fine particles of sand, which
require the microscope to make them
visible remain a long time suspended,
and are carried with very low velocities.
The material which forms blue and other
clays is deposited during periods of low
water and sluggish currents, and micro-
scopic sand is always present in these
alluvions. Many strata of hard blue
clay were encountered by the piers of
the St. Louis Bridge, when sinking them
through the 80 feet of deposit overlying
the limestone bed of the river. None of
these were more than six or eight inches
thick, and each was, no doubt, deposited
during a single period of low water.
They were alternated with layers of
sand and gravel.
Caving banks generally occur when
the river is falling, because then the sup-
port or pressure of the river having been
withdrawn from them, such as have been
undermined by the rapid highwater cur-
rents topple over into the stream and
thus add temporarily to the normal
charge of sediment then carried in suspen-
sion. It is quite possible that the high
charge of 608 grains per cubic foot, with a
velocity of only 2.57 feet per second,
was partly due to caving banks a few
miles above.
Diagram No 2 shows that in the eight
months during which the sediment ob-
servations were made at Columbus, there
were six periods when the river fell from
levels previously attained, and at each
period the quantity of suspended matter
diminished at once with the loss of cur-
rent. This instantaneous evidence of the
intimate relation between the velocity
and the quantity carried, so clearly
shown by the weekly mean of these quan-
tities on the diagram, would be less ap-
parent in curves representing each ex-
periment. Slight errors in weight, or in
current measurements and local causes,
such as the caving in of the banks above
the observer, might make the sympathetic
action between the current and sediment
appear less harmonious if the mean of a
number of experiments were not taken.
The weekly mean taken by the authors
of the report, thus tends to bring out
in bolder light the force of their own
testimony against them.
In addition to errors in measurement,
and caving banks, other causes, such as
the differently charged waters of tribu-
taries moving with altered velocities in
the parent stream, and the difference in
the time required for different kinds of
sediment to deposit, may each operate
to modify the results of such experiments
as these we are discussing, and hence ab-
solute synchronism in the curves of ve-
locity and sediment cannot be expected.
This agreement is however, so marked
in diagram No. 2, as to bear excellent
testimony to the care with which Messrs.
Webster and Fillebrown conducted the
experiments at Columbus.
THE BED OP THE RIVER.
The wonderful discoveries made by
Humphreys and Abbot, through their
unique method of investigating dy-
namical phenomena, are supplemented
with others in geology scarcely less sur-
THE HYDROLOGY OF THE MISSISSIPPI RIVER.
221
prising. On page 14 of their Report we
find the following:
" For instance, the Mississippi had al-
ways been regarded as flowing through
a channel excavated in the alluvial soil,
formed by the deposition of its own
sedimentary matter. So important an
assumption was inadmissible; and great
pains were accordingly taken to collect
specimens of the bed wherever soundings
were made, and by every means to ascer-
tain the depth of the alluvial soil from |
Cape Girardeau to the Gulf. This in-
vestigation has resulted in proving that
the bed of the Mississippi is not formed
in alluvial soil, but in a stiff, tenacious
clay of an older geological formation
than the alluvion."
The following occurs on page 91:
" What then constitutes the real bed
of the river, upon which rest the moving
sand-bars, and the new willow-batture
formations? From the mouth of the:
Ohio down, at least as far as Ft. St. ,
Philip [forty miles above the Gulf] it '
seems to be composed of a single sub-
stance, a hard, blue or drab-colored
clay."
The age of the bed of the river is a mat-
ter of little practical interest to the pub- !
lie, and I do not therefore propose to dis- 1
cuss it. But whether it is composed of
a clay that yields slowly to the strong-
est currents, and resists their action
" almost like marble," is a question of
the utmost importance to the people of \
the whole country. The intelligent
reader need only be told that within
three years, the Congress of the United !
States has been advised to incur an out- 1
lay of forty-six million dollars, based on
the proposition that the bed of the Mis- j
sissippi will not yield to the action of
its strong current, to have his curiosity
aroused upon this important question.
The existence of this substratum is
asserted by Humphreys and Abbot in i
the most confident manner, as a fact con- \
clusively established by the numerous
soundings of the Survey with prepared
leads. We are told on page 90, in ref- !
erence to these soundings, that " The de- i
tails of these operations are explained in j
Chapter IV, and the results exhibited in j
Appendix C."
Turning to Chapter IV, to learn by
what devices this clay had been discov-
ered "beneath the moving sand bars and J
the new willow batture formations," we
find them to consist of nothing more
than " a sounding chain and plummet."
The latter is thus described : " The
sinker, varying from ten to twenty lbs.
in weight according to the force of the
current, was a leaden bar whose bottom
was hollowed out and armed with grease,
in order to bring up specimens of the
bed of the river; the patent lead was
also used for the latter purpose."
Now, when it is remembered that no
borings were made either on the banks
or in the bed of the river to test the ex-
istence of this unyielding clay, the reader
will appreciate how astonishingly the re-
sults of these soundings have been mag-
nified, if he will examine them in Ap-
pendix C, and compare the facts there
recorded with the extravagant reference
made to them in the report.*
On page 90, under the heading of " Geo-
logy of the channel" we are told that "A
knowledge of the character of the bed of
the Mississippi River is of the highest
practical importance, as will be hereafter
seen, and great efforts have been made
to acquire it."
The above extract, and the statement
on page 14, that "great pains were ac-
cordingly taken to collect specimens of
the bed wherever soundings were made,"
caused me to look forward to an ex-
amination of the results of these " great
efforts," as a matter of considerable labor,
more especially as they had been spoken of
on page 412, as "an extended series of
measurements." I carefully examined
the first eleven tables of soundings in
Appendix C, and found that they did
really constitute " an extended series of
measurements;" for they comprise the
only recorded lines of soundings made by
Humphreys and Abbot on the Missis-
sippi River between Cape Girardeau and
Vicksburg; a distance of 650 miles !
The remaining tables are the record of
soundings made at Vicksburg and below
that point down to Fort St. Philip, a
distance of 500 miles more.
As five of the eleven lines were run
* The record of the artesian well at New Orleans is given
in the report, and reference is made to it on page 465 to
prove that the river deposits overlying this ancient and
imaginary clay, extends only 40 feet below the level of the
gulf at New Orleans, (or 55 feet below high water mark,)
As a sound cedar log was struck 153 feet deep by the
auger, aud is reported in the record, and therefore lies 98
feet deep in this marble like clay, it is to be regretted
that an explanation of how it got there, was not given
the report.
222
VAN NOSTEAND'S ENGINEERING MAGAZINE.
across the river at Columbus, and two at
Lake Providence, the other four had
necessarily to be considerably extended
to make " this investigation " into the
geology of 650 miles of river a very
thorough one.
About fifty soundings, more or less, were
made on each one of the eleven lines,
but the grease was evidently bad, or the
patent lead was a failure, for, on the first
line of these numerous soundings, only
one solitary sample was obtained. The
grease seems to have given out altogether
on four of the lines. When the two
were run across at Lake Providence this
must have been the case, or it was a bad
day for geological research, because no
specimen whatever was obtained in either
of these two lines, and thus a space
nearly two hupdred miles long, between
Napoleon and Vicksburgh — was not sam-
pled at all. The prepared leads appear
to have worked badly on the third line
also, as only two samples were obtained
there. In the entire eleven lines of
soundings, that were made across the
river in this 650 miles, there were only
thirty-five samples of the bottom secured !
The different kinds of material were
carefully noted in a separate column un-
der the head of "Remarks."
When we reflect that each of these pre-
cious specimens was deemed to be a key to
an unwritten record running away back
into the dim past, where azoic and
palaeozoic cycles inclose the sublime gen-
esis of the Father of Waters, we cannot
fail to note the terse expressions with
which, in such simple terms as " Gravel,
Clay, Sand, or Mud" these antediluvian
treasures are recorded. This brevity is
however, fully compensated for in Chap-
ter II, where "the results exhibited in
Appendix C are discussed."
Let us now examine the conclusive
evidence given of the existence of this
unyielding substratum by "the samples
of the bottom which were carefully pre-
served for examination and comparison."
The thirty-five samples secured in this
650 miles of river, when shorn of the
imposing verbiage with which they are re-
ferred to in the report, certainly constitute
a very small basis on which to rest the
positive statement that the bed of the
Mississippi is composed of an unyielding
clay, even if we suppose each one of the
samples was a specimen of clay • but
this small basis becomes supremely ri-
diculous when the fact is stated, that
twenty-five of- these samples actually
consisted of pure sand, and that only
seven of the whole thirty-five were
of clay alone ! And then again, each
one of the seven areas thus sampled
by the prepared leads was probably not
larger than the palm of a man's hand !
Moses, when stopped on Mount Pis-
gah, might as well have tried to analyze
the subsoil of the promised land by gaz-
ing at it, afar off, as for these gentlemen
to tell anything about a mythical sub-
stratum of clay under the shifting depos-
its of the river by means of their greased
leads. The present age demands proof,
not guesswork and assertion, and it is
utterly impossible that anything adhering
to the bottom of a tallowed plummet
from the bed of the Mississippi, can fur-
nish any evidence whatever as to the kind
of material that lies one inch below
where the sample was thus secured.
It is scarcely necessary to refer to the
soundings below Vicksburg, after this
statement, except to say that eighty-two
lines were run in that part of the river,
and that 56 of these were made in 45
miles of the river near New Orleans. In
116 miles of the river between Vicksburg
and Natchez, only two samples were ob-
tained. Of the total 93 lines run, no
samples were obtained in 35 of them, and
of all the samples taken, only about one
in four was of clay alone, while more than
one-half of the whole number were of
pure sand. It is needless to say that all
of the samples were just such materials as
the river is constantly transporting in
suspension, and that they do not furnish
a particle of evidence that the bed is
formed of any other substance than its
own deposits.
Blue clay is one of the deposits or
alluvions of the river, and is found every-
where in the alluvial basin, in layers al-
ternating with the sand, gravel and earthy
deposits, which compose its bed and
banks. It is found deposited in old
sunken wrecks,* on sunken rafts, and on
the "rack heaps," or accumulations of
drift-wood which lodge against snags
* Col. Andrews states that a barge which lay submerged
during only two seasons of low water at the jetties had a
stratum ot blue clay nearlv afoot thick deposited in it,
which was so tough and sticky that the men could scarce-
ly dig it out, because it adhered to the shovels so tena-
ciously.
THE HYDROLOGY OF THE MISSISSIPPI RIVER.
223
or islands. It was doubtless an old
steamboat wreck, or a rack heap which
caused the loss of the sounding leads,
referred to in Chapter II, and which
marked the chain with this blue clay
thirty feet above its broken end.
Yet the clay, found on the chain and
the uneven depths where it was broken,
led the authors of the report to suppose
that the river bottom was " full of
blue clay ridges and lumps many feet
high."
One proof of the fact that the bed of
the river does yield readily to the action
of the current will be seen in the great
number of curved lakes lying on each
side of its present bed, and extending
from the upper to the lower end of
the alluvial district. Each one of these
was once a part of the river channel.
The following correct explanation of
their formation is copied from page 96 of
the report :
" It occasionally happens that by this
constant caving, two bends approach
each other, until the river cuts the nar-
row neck of land between them and
forms a 'cut-off,' which suddenly and
materially reduces its length. The in-
creased slope of the water surface at once
makes this new bed the main channel of
the river. The upper and lower mouths
of the ' old river ' are gradually silted up
with sediment, drift-wood, etc., until
eventually one of the crescent-shaped
lakes so common in the alluvial region is
formed."
The rapidity with which the current
sometimes cuts away the tough blue clay,
so frequently met with in its bed and
banks, may be inferred from the follow-
ing account of the formation of a cut-off,
given by Major Suter, IT. S. Engineers,
in his report :
"Davis', one of the most recent of
these cut-offs, and also the largest,
occurred in 1867. It cut off Palmyra
Bend, eighteen miles below Vicksburg,
a bend which was eighteen miles long
while the distance across the neck was
only 1200 feet. The exact slope of the
river at the time* is not known, but it
was probably not far from 0.3 foot to
the mile; therefore the difference of
level on the two sides of the neck was
about 5j feet. When the river broke
through, the whole of the fall had to be
absorbed in the 1200 feet of distance,
making a rate of about twenty-four feet
to the mile; and it can readily be
imagined that the whole immense flood
volume of the Mississippi, flowing with
the enormous velocity due to this great
slope, produced very marked effects.
The roaring of the waters could be heard
for miles; and in the course of a few
hours, a channel a mile wide, certainly
over a hundred and probably nearly two
hundred feet in depth, had been exca-
vated."
It is impossible to reconcile the ex-
cavation in a few hours of " a channel a
mile wide and certainly over a hundred
and probably two hundred feet deep,"
with the existence of a clay that "resists
the action of the strong current, almost
like marble." Such a clay is un-
doubtedly a myth.
THE PRACTICAL IMPORTANCE OF THESE
TWO QUESTIONS.
Let us now look at the immense prac-
tical importance of these two facts which
are so stoutly and dogmatically denied
by Humphreys and Abbot. If the quan-
tity of suspended sediment is regulated
by the current, and if the bed of the
river is formed of its own sedimentary
deposits, instead of this unyielding and
marble like clay, then it is entirely prac-
ticable to lower its flood line or slope,
and deepen its channel by simply con-
structing light willow or brush dams
during low water on the shoals which are
then dry, or nearly so, at the various
wide places in the river where the bars
always exist. These dams would cause
the deposit of more sediment on the
shoals, by checking the current, and
would deepen the contracted channels that
would remain by increasing the current in
them. In this way (without undertaking
to straighten the river, which would be
supremely foolish, and impracticable),
the high water channel would be brought
to a comparative uniformity of width, by
gradually encouraging, from year to
year, the deposition of sediment over the
wide expanses, and this uniformity of
width would produce a uniformity of
depth, which in turn would insure a uni-
formity of current, and this would prac-
tically stop the caving of the banks. A
uniformity in the width of the high
water channel would do more however
than all this, for it would lower the
224
van nostkand's engineeking magazine.
flood line and practically dispense with
the use of levees in protecting against
overflow, an area equal to the state of
Indiana.
If Humphreys and Abbot's theories are
sound, such an improvement of the
river channel, and such abandonment of
the levee system, is totally impracticable.
The following quotations show that
these dangerous theories have been
adopted by the United States Levee
Commission, which recently recommend-
ed a system of levees below the mouth of
the Ohio at an estimated cost of nearly
$46,000,000. It says in its report,* page
8, [Ex. Doc. 127 H. K. 43d C. 2d Ses.]
that "the assumption that the river
water is always charged with sediment
to its maximum supporting capacity
'* * * has been shown by three years
of accurate daily observations, at Carroll-
ton and Columbus, to be utterly unfound-
ed. Indeed, it often happened that the
amount of sedimentary matter per cubic
foot of water was greater in 16w than in
high stages of the river, and never was
there ever any fixed relation between
these quantities. In other words, Missis-
sippi River water is undercharged with
earthy matter, and therefore no reason-
able reduction of its flood velocity by
an outlet will produce a deposit in the
bed below.1'
By reference to pages 135 and 137 it
will be seen that this extract contains an
astonishing exaggeration. Instead of
three years, the current and sediment
observations only occupied eight months
at Columbus, and one year at Carrollton.
When we remember that the junior
author of the report on the Mississippi
river, was a prominent member of the
Levee Commission, and that the senior
author, as Chief of Engineers, warmly
endorsed its report, it is difficult to recon-
cile this careless statement with the
unusual scientific exactness which re-
quired four decimals to record their
measurements of the current, (see page
244). In this case the reader is con-
verted to a false theory by being gravely
assured that it has been demonstrated
conclusively by three years of daily accu-
rate measurements at the upper and
lower ends of the delta ; and in the other
case, he is captivated by the wonderful
*This report was reviewed by me in the Scientific
American supplement.
precision which tells him to the ten
thousandth part of a foot, the varying
distances which the flowing stream has
traveled at different depths below the
surface, in a second of time ! As this
statement is an inexcusable exaggeration,
and as such exact determination of cur-
rent velocities is utterly impossible by
any known method of measurement, it
follows that theories sustained by such
testimony, cannot constitute advances in
science.
On page 16, of the report of the
Commission, we find the following: "It
is asserted in the most confident manner
that the river is flowing in a bed com-
posed of its own deposit, with dimen-
sions regulated in accordance with its
own needs ; and hence that the increased
velocity resulting from the confinement
of its flood-volume between levees will
rapidly excavate its bed to a correspond-
ingly greater depth."
" This reasoning, if true, would establish
conditions singularly fortunate for the
Levee system; but unluckily the wish has
been father to the thought. Uncom-
promising facts show that the premises
and conclusion are both erroneous for
the lower Mississippi. Very numerous
soundings, with leadsr adapted to bring
up samples of the bottom, were made by
the Mississippi Delta Survey throughout
the whole region between Cairo and the
Gulf. They showed conclusively that
the real bed, upon which rests the shift-
ing sand bars and mud banks made by
local causes, is always found in a stratum
of hard blue clay, quite unlike the pres-
ent deposits of the river. It is similar
to that forming the bed of the Atcha-
falaya at its efflux, and, as is well known,
resists the action of the strong current
almost like marble."*
The results of these soundings with
prepared leads are not only unduly mag-
nified in the above statements, but the
reader is also misled by the assurance
that they conclusively proved the ex-
istence of this marble-like clay.
On page 17 of its Report this state-
*It is assumed, that because the efflux of the Atchaf alaya
has not deepened under the action of the current, the clay
bottom there will not wear and must be something differ-
ent from the ordinary river deposits. A bottom of sand
would remain just as permanent when the capacity of the
efflux is adjusted to the volume, of discharge. The cross
section of the bed, whether of clay or sand, will inevitably
increase or diminish with an increase or diminution of
the volume.
THE HYDROLOGY OF THE MISSISSIPPI RIVER.
225
ment is made: "If we guard against
these crevasses by raising and strength-
ening our levees, an elevation of the high
water mark proportional to the increased
volume will be sure to occur."
"To contain a quart of water a vessel
must have exactly the requisite number
of cubic inches; and a like principle ap-
plies with equal force to water in mo-
tion."
This is quite a novel proposition. How
a like principle can apply to water in
motion, I am at a loss to discover. The
number of cubic inches in a quart cup is
a question of space or volume only.
When the water is in motion, force and
time enter into the problem, and they
make an elevation of the high water mark
exactly proportional to the increased vol-
ume, a simple impossibility, even if the
bed of the stream should not deepen.
That the height would increase with
the volume, as in the case of a quart
cup, is simply an absurdity. But
when problems in dynamics are solved
without considering the elements of
space and time, and the profound
mysteries of remote geologic epochs, are
unlocked with a greased sounding lead,
we need not be surprised to learn that
the most important questions in river
hydraulics may be illustrated and ex-
plained with a quart cup.
If the bed of the river cannot yield,
and all the crevasses in the levees are
closed, the sides of the quart cup — or
the levees, must be built up ten or eleven
feet higher than ever before, and, there-
fore, the Levee Commission recommends,
and the Chief of Engineers earnestly en-
dorses, a system of levees at an esti-
mated cost of $46,000,000, and all be-
cause the bed of the river has been con-
clusively proved by " an extended series
of measurements," to be of an unyielding
material.
A few years ago the Chief of Engi-
neers of the U. S. Army, being equally
as well convinced that the steamboat
smoke pipes were, like the bed of the
river, unyielding in their nature, and
that they were too high to pass under
the bridge, which spans the Mississippi
at St. Louis, accordingly recommended
that a canal with a draw-bridge, through
the bridge approach, to accommodate
these unyielding smoke pipes, should be
dug around the end of the bridge in the
Vol. XIX.— No. 3—15
ancient geologic blue clay in Illinois, at
a cost of over three million dollars !
The fact that the river water was
proved by "a glance at the two dia-
grams " to be always under-charged with
sediment, was an assurance that the canal
would be a success and would not silt up.
But Congress did not look with favor on
this plan. Doubts as to the unyielding
nature of the smoke pipes were openly
expressed, and while the canal plans and
estimates were being prepared the
lucky discovery was made that the
whole difficulty could be avoided by
putting hinges in the pipes; and so the
three million of public treasure was
saved, and the commerce of the river
now flows under the bridge without let
or hindrance.
PRACTICABILITY OF DEEPENING THE RIVER
AND LOWERING THE FLOODS.
The inclined plane formed by the sur-
face of the river from the highlands
down to the sea is called its slope. The
intensity or degree of force exerted by
the water in its passage depends upon
the steepness of this slope. The amount
of the force depends upon the mass or
volume of the water and upon its veloci-
ty, the current being the result of the
slope. The friction of the bed is the
chief element which retards the current.
The slope, the volume, and the friction
are therefore the chief agents which
determine the speed of the current.
Others modify it somewhat but they
need not be considered here.
Now if the reader will bear in mind
that the water is charged with sediment
according to its velocity, and that it flows
through a bed of precisely the same
kind of material it is carrying in sus-
pension, and that if its velocity is in-
creased it will take up a greater charge
from its own bed, or if its current be
slackened it will drop some of its charge
in the channel, and add to its bed, he
will understand the important part
which the speed of the current performs
in the problem. Through the whole
alluvial basin from Cairo to the sea, the
river must discharge as much sediment
into the sea and over its banks, as its
tributaries pour into it. If it discharged
less, its channel would shoal up and its
slope be steepened by the excess re-
ceived from its tributaries.
226
VAN NOSTRANTTS ENGINEERING MAGAZINE.
If it carries more to the sea than is
brought down into it from the tributaries,
the excess discharged must be taken out
of its own channel, and this would
deepen it, and lower the slope. From
this it is evident that there must be
some means by which nature adjusts
the speed of the current to suit the
needs of the river. This is done by
the relation which exists between the
rate of current and the quantity of
sediment carried in the water. If the
velocity be too great the deepening of
the bed follows. This lowers the slope
and the current becomes less rapid. If
the velocity on the contrary be too slow,
deposition in the channel continues to
take place until the river bottom is
raised and the slope steepened, and a
higher velocity is produced. These are
the inexorable results of the relation be-
tween the current and its burden.
The river's slope, being the surface of
the water, determines the height of the
levees, and is therefore the vital question
in the reclamation of the lands from
overflow.
We see how the current alters the
slope by the opposite processes of de-
posit and scour. We want to lower the
slope to prevent overflow. When the
current is too rapid, deepening is the
process nature sets up in the bottom of
the river, and gradually the slope is re-
duced and a normal current succeeds.
To reduce the slope, we must temporarily
increase the current. This can be done in
two ways. Friction of the bed is the ele-
ment which retards the velocity. Where
the river is excessively wide, it will have
more frictional resistance to overcome,
and must there have a steeper slope. If
we reduce its width at such place, the first
effect will be an elevation of surface
above. This will create a rapid current
through the narrowed part, and it will
be deepened there, and the elevation of
surface above will then subside; but the
current will still continue to be rapid, be-
cause the narrow and deep form of chan-
nel created will have less friction than the
former wide one, and the rapid current
will therefore continue to deepen the bid,
until the original slope is so lowered that
the current through the contracted chan-
nel is gradually reduced to the normal rate
again. When this is done it will be
found that the flood line or slope has
been permanently lowered at that
locality. This necessarily leaves the
slope steeper immediately above the
locality thus treated, and this induces a
more rapid current, and consequent deep-
ening of the bed, and lowering of slope
still higher up. In this way the altera-
tion of slope at one locality ultimately
extends up to the head of the alluvial
district. Of course this could not occur
unless the most sensitive relation existed
between the rate of current and the
quantity of sediment suspended by it.
Nor could it Occur except where the bed
of the river is formed of the same ma-
terials which it carries in suspension, or
of materials easily eroded or moved by
the current.
Another way to lower the slope is to
increase the volume of water in the chan-
nel, because friction does not increase in
an equal ratio with the volume. The
greater is the volume, the lower is the
slope, is a lesson taught by every part of
the river, and by every outlet and bayou
in the alluvial basin. This is because the
proportion of friction to volume becomes
less as the volume is increased, and,
therefore, if the volume is increased, a
lower slope will produce the normal rate
of current, or that rate which will carry
its charge of sediment to the sea without
either loss or gain. It is impossible to
maintain permanently any greater rate
of current than will suffice to do this, in
any sediment-bearing river in the world
through its alluvial district. Bayou
Atchafalaya at Red river carries a por-
tion of the Mississippi to the sea with a
fall of over six inches per mile, while
the main river pursues a pathway more
than three times as long, with a fall
of less than two inches per mile. The
greater friction in the smaller channel
alone prevents a high rate of current
through it. Its slope has been adjusted
to maintain the rate required to discharge
its waters and their earthy burden with-
out injury to its own channel. If it were
closed and its waters were compelled to
flow in the main river, the first result
would be an elevation of the surface and
a more rapid current ; a deepening of
the bed would follow this, and a lower-
ing of the slope would be the perma-
nent result.
Lower levees would, of course, then be
practicable. This teaches us that if we
THE HYDROLOGY OF THE MISSISSIPPI RIVER.
227
wish to lower the floods and deepen the
channel we must close the outlets and
crevasses, and convey all of its waters
through one channel to the sea. Hum-
phreys and Abbot tell us precisely the
contrary.
After an elaborate discussion on the
effect of outlets and crevasses, they say :
(page 420) " The conclusion is then in-
evitable, that so far as the river itself is
concerned they are of great utility.''''
The Levee Commission's report con-
tains a table (page 59) from which it will
be seen that from Cairo to Memphis (235
miles), there are 70 miles of crevasses and
gaps in the levees, while many more ex-
ist below Memphis. It is well known
that since the Rebellion in 1861, these
levees have been going to destruction.
Certainly a sufficient number of outlets
and crevasses have been existing and oc-
curring here in the last 17 years to test
their utility and the value of the opinion
of these gentlemen on the subject.
Major Suter, U. S. Engineers, has made
the, most recent survey of the river, and
in his report, 1875 (Ex. Doc. 19, Page 16,
43d Congress) he says: ''Within the
memory of living pilots the shoal water
has extended down from Plum Point, one
hundred miles above Memphis, to Lake
Providence, fifty miles above Vicksburg,
a total distance of 450 miles; and as these
disturbing causes wxill act with more
vigor every year, it is time that we should
fairly face and realize the fact that, un-
less speedily checked, there are natural
causes at work which will eventually
destroy the navigability of the Missis-
sippi and its tributary streams." Com-
ment is unnecessary.
Since 1842, two large outlets have oc-
curred, from artificial causes, through
the narrow strip which separates the
river from the gulf a few miles above the
head of the passes. Through these
about one-fifth of the river is now dis-
charged. They are known as Cubitt's
gap and The Jump. Surveys made in
1875 when compared with that of Talcot's
made before they occurred, have revealed
the fact that the depth of the river below
the lowest one, has been reduced from
over forty to thirty feet, and the size oj
the river bed is fully one-quarter less
than it was before these crevasses occur-
red. I called public attention to this
startling fact, to show that crevasses do
cause shoaling in the river channel. Here
is the explanation for this deposit, given
by Genl. Humphreys. (See Appendix L,
H. and A.'s report, 1876.) " During the
low water stage of the river, there is a
stratum of salt water many feet thick at
the bottom in the passes and in the wide
part of the river at the head of the passes,
and extending above that point some
distance, which has but little current
either way compared to the current of
fresh water on top of it; the earthy mat-
ter suspended in the river water falls
upon the bottom of the river thus occu-
pied by salt water, just exactly as it falls
upon the bottom of the gulf out at sea
beyond the bars, and during the low
water stage a deposit is thus made on
the bottom of the river."
On page 420 we are told that " there
is no evidence that any filling up of the
bed ever did occur in consequence of a
high water outlet; and, moreover, that it
is impossible that it ever should occur,
either from the deposition of sedimentary
matter held in suspension, or from the
accumulation of material drifting along
the bottom."
In view of the stubborn fact that this
enormous shoaling has occurred since
Cubitt's crevasse was made, it is plain
that the above positive statement must
be taken cum grano salis. Indeed it
seems important for the credit of its
authors that it be taken with a very large
quantity of salt ; for it appears that if
there is a stratum of salt water under
the river water, a shoal will occur below
a crevasse. The feeblest current then,
according to Gen'l Humphreys is not,
with salt under it, capable of carrying so
much sediment as the most rapid cur-
rent; and the distribution of the sedi-
ment appears to be controlled by law
if it has brine below it. The river
water then ceases to be " always
undercharged," and the relation between
cause and effect is restored. The
virtue of salt water is truly marvelous.
"Old assumptions which experimental
investigation has long since shown to
be utterly unfounded in fact," become
demonstrated truths, if a stratum of it
be under the river water.
On page 415 of the report of Hum-
phreys and Abbot, the following quota-
tion is made from an article published
by Major (now General) J. G. Barnard,
228
VAN NOSTRAND'S ENGINEERING MAGAZINE.
XJ. S. Engineers, in Debovfs Review in
1850.
" ' I find this principal laid down in
the work of Frisi, ' On Rivers and Tor-
rents,' which was placed in my hands by
W. S. Campbell. He quotes and con-
firms the rules established by another
engineer, Guglielmini, which are that
4 the greater the quantity of water a
river carries, the less will be its fall? and
' the greater the force of the stream, the
less will be the slope of its bed.' And,
again, * the slope of the bottom in rivers
will diminish in the same proportion in
which the body of water is increased,'
and vice versa. These rules have their
explanation in the facts that the beds of
rivers, of the character above mentioned
[like the lower Mississippi], are capable
of resisting, unchanged, only a certain
velocity of current ; and, on the other
hand, that the sedimentary matter con-
tained in the river water, requires a cer-
tain degree of velocity to keep it in sus-
pension. From the counteracting tend-
encies of the above two causes, a mean
becomes established, at which the cur-
rent ceases to deposit its sediment, and
the bottom ceases to be abraded ; in
other words, the bottom becomes perma-
nent. But if, from Any cause, such as
throwing off a portion of the water
through a waste-weir, the velocity of the
current is diminished, it is no longer
able to maintain its sediment in suspen-
sion, but will continue to deposit in its
bed, until, through the elevation of the
bed, its velocity again becomes what it
was before it was disturbed, sufficient to
maintain its sediment in permanent sus-
pension." '
As this proposition is fully sustained
by the Columbus and Carrollton experi-
ments, and is conclusively proved by the
phenomena presented all through the
alluvial basin, the summary manner in
which it is disposed of by Humphreys
and Abbot is amusing. They say:
" It will be noticed that two import-
ant assumptions are necessary to sup-
port this reasoning: First, that the hot
torn of the Mississippi is composed of its
own alluvion, which can be readily acted
upon by the current; and, second, that its
water is always charged with sediment to
the maximum capacity allowed by its
velocity.
" Throughout the whole distance from
Cairo to Fort St. Philip the true bed con-
sists of a tenacious clay which is unlike
the alluvial soil, wears slowly under the
strongest currents, and is, proved, by
conclusive evidence, to belong to a
geological formation antecedent to the
present. This disposes of the first as-
sumption.
" We come, then, to the second as-
sumption, viz: that the water is at all
times charged with sediment to the
maximum capacity allowed by its vel-
ocity. * * * A glance at the two
diagrams (plates XII and XIII) is suf-
ficient to demonstrate the falsity of the
assumption, that Mississippi water is
always charged with sediment to the
maximum capacity allowed by its
velocity. * * * The second assump-
tion is, then, as untenable as the first."
THE RELATION BETWEEN THE CURRENT
AND SEDIMENT IS EXCEEDINGLY SEN-
SITIVE.
Owing to the great width of .the
river at the head of the passes, the
depth at the entrance into each pass
is much shoaler than it is in the
pass. South pass is about 700 feet wide,
and over thirty feet deep, but the water
entering it was about 2,800 feet wide half
a mile above its entrance, and at this
place the channel was but fourteen feet
deep. To concentrate this 2,800 feet
into a narrow and deep channel, I erect-
ed, with other more substantial works, a
dam or willow screen 1,900 feet long
across the current on the eastern side of
this shoal. The dam consisted of a
single thickness of willow mattress held
in a vertical position by piles, the willow
work being only two feet thick, and the
depth of water being from twelve to six-
teen feet. Of course the current passed
through the willows with but little hind-
rance. It was not intended to be an im-
pervious dam, and the whole structure
was only strong enough to resist stormy
weather. It was built with the practi-
cal knowledge that a very slight retarda-
tion of the current will cause a deposit.
Two floods caused so great a deposit both
above and below it that a small row boat
can not now get to the dam at low
tide. In another season or two, vegeta-
tion will probably cover this deposit and
extend many hundred feet above the dam,
MOMENTUM AND VIS VIVA.
229
and an area of more than one hundred
acres of dry land will occupy the space be-
tween the dam and the main land below.
The channel through the shoal is now
twenty-two feet deep at low tide.
In the Department of Public Works
at St. Petersburg I was shown a device
similar to a Venetian blind, formed with
small ropes and wooden slats, that was
said to have been successfully used on
the Volga for the same purpose as the
willow dam I have described.
These results can be explained on no
other theory than that the amount of
sediment carried is strictly regulated by
the velocity of the current. The burden
can only be carried by the expenditure
of force. Nature adjusts the quantity to
the force, and if we absorb any portion
of the force even by the resistance of a
porous willow dam, less force will remain
to carry the burden and some of it must
then fall to the bottom.
It is simply impossible that the work
done, or load carried, can be greater than
the force expended, or that the effect can
be greater than the cause; and hence we
cannot compel the force that is required
by nature to transport the sediment, to
do any other work, even so much
as the turning of a mill wheel, or
absorb any part of it by the friction
of a dam made with open willow twigs,
■ or even with one made with a fish net,
without lessening, by so much, the force
which is being expended in transporting
the sediment. If we do, a deposition of
a portion of the load must result, and it
must continue to fall until, by the raising
of the bed, a new regimen is established.
MOMENTUM AND VIS VIVA.
By S. BARNETT, Jr.
Written for Van Nostrand's Magazine.
In the June number of Van Nostrand's
Engineering Magazine, we find the
following from Prof. Skinner: "....,
I was arguing that writers who prefer to
derive the unit of mass by definition
from the unit of force ought to first
make their arbitrary unit of force inva-
riable, so that there should be a definite
ratio between the units of mass and of
force in the two systems; and so that
students could pass by simple multipli-
cation or division from one to the other."
Now, not to dwell upon the fact that
some unit of mass or other must be de-
termined before we can fix a unit of
force, we may inquire what would be the
nature of this ratio of the unit of mass
to that of force. If the quotient of mass
divided by force is an arithmetical num-
ber, that is of zero dimensions, mass and
force are the same thing. Force would
be nothing but mass, or mass nothing
but force. But if mass is not force, the
ratio of the two must be of dimensions
other than zero in, at least, one denomina-
tion; say length or time, and this ratio
will depend upon such other unit or
units. It is necessary to show how the
ratio so depends, and this Professor Tait
showed in his Glasgow lecture in com-
paring force and momentum, or, at least,
partly showed, but which Prof. Skinner
said seemed to him " an arrangement of
no validity."
Further, Prof. Skinner says : "But if
force is nothing but a rate of doing woi'k,
then work is nothing but the action of a
rate of doing work, and we may just as
well say that force is force and work is
work, and confess that we know nothing
of either of them." We should hardly
accept this, however, as the conclusion of
the whole matter. There is not the least
difficulty in the conception and exact ex-
pression of the product of the space
passed over into the rate of change of
momentum. In mathematical symbols
work =
/*
d(mv)
~dt
ds.
Also the rate of
doing work per unit of length is force or
the rate of change of momentum.
i.e.
dw = d r\
ds ~ ds9J
d(mv)
w
ds —
d(mv)
The non-mathematical reader should
230
VA.N NOSTRAND'S ENGINEERING MAGAZINE.
know that work is the sum of the ele-
mentary spaces passed through, each
multiplied by the rate of change of mo-
mentum per unit of time at the point.
As regards the remarks of Thomson
and Tait that, " It is therefore very much
simpler and better to take the imperial
pound " for the unit of mass, &c, we
simply add — " Unquestionably so, for all
practical purposes." And indeed the ab-
solute unit of force only needs an abso-
lute unit of mass no matter how derived;
the assumption is only necessary so far
as the unit of force is concerned. The
practical difficulty of replacing units of
mass by their relations to those of time
and length has nothing to do with the
theoretical perfection of the method.
REMARKABLE CHANGES IN THE EARTH'S MAGNETISM.*
From "Nature."
One of the most important, scientifi-
cally, of the special lectures at the Geo-
graphical Society, was that by Capt.
Evans, in March last, on the subject of
terrestrial magnetism. The concluding
portion, especially, is of high scientific
importance. Capt. Evans gave a histori-
cal sketch of the subject of terrestrial
magnetism from the time of the dis-
covery of the dip of the magnetic needle.
After speaking further on various depart-
ments of his subject, Capt. Evans went
on to say:
We have now passed in review the
successive stages of development of our
branch of knowledge, from the pregnant
epoch when its principles were enun-
ciated by Gilbert, till the period when
the well-directed munificence of his own
and other Governments dotted the
earth's surface with observatories, and
despatched land and sea expeditions,
specially equipped, for the determination
of the magnetic elements. We have
seen how a few earnest and gifted men
have, by long and patient analysis, laid
the foundations for future generations to
build upon as regards theory, and un-
ravelled the apparently inextricable web
surrounding the needle's daily and yearly
movements; tracing these movements to
their primary source, the sun: and how
by the perseverance of states and of in-
dividuals, we are now in possession of
accurate knowledge as to the distribution
of magnetism over the surface of our
globe, as represented by the variation
and dip of the needle, and by the meas-
* From Lecture at the Royal Geographical Society,
March 11, by Captain F. J. Evans, C.B., F.K.S, Hydro-
grapher to the Admiralty.
ure of the force connected with those
component elements. But the task,
from a scientific point of view, is far
from completed while we remain in
ignorance of the causes of greater
changes in the earth's magnetism going
on from year to year, and so on, possibly
through geons of time. From a practical
point of view^ so far as the interests of
men are concerned, the collection of re-
cords will be a never ending task, for
every generation must observe and chart
the magnetic elements of its time.
The subject of secular change is thus
one of such great interest that the re-
maining portion of my lecture must be
chiefly devoted to it. The active mind
of Halley was drawn, as one of the first,
to the probable nature of the causes;
collecting such observations of the varia-
tion of the compass as had then been
made, and projecting them on polar
maps, he found that the convergence of
the several directions of the needle led
to two points in each hemisphere. On
this he enunciated the proposition "that
the whole globe of the earth is one great
magnet, having four magnetical poles or
points of attraction; near each pole of
the equator two; and that in those parts
of the world which lie near adjacent to
any of these magnetic poles the needle
is governed thereby, the nearest pole
always being predominant over the more
remote." Halley saw, as he confessed
with despair, the difficulties attending
the proposition, " as never having heard
of a magnet having four poles," but there
were the facts manifested by the earth,
and he was too sagacious and sound a
CHANGES IN THE EARTH'S MAGNETISM.
231
philosopher to pass them by. He ac-
cordingly propounded a theory which,
however fantastic it may now appear,
and perhaps did at the time he wrote,
has nevertheless within it the fire of
genius, and may probably be found yet
to contain some sparks of truth. To
account for the four poles, and at the
same time for the secular change of the
variation, he conceived that the earth
itself might be a shell, containing within
a solid globe, or terella, which rotated
independently of the external shell; each
globe having its own magnetic axis pass-
ing through the common center; but the
two axes inclined to each other and to
that of the earth's diurnal rotation. It
is not difficult to follow the movements
of the consequent four imaginary poles
in solution of the problem.
Hansteen working at the same prob-
lem a century after Halley [1811-19],
and much on the same lines, came nearly
to the same conclusion with regard to
the four poles of attraction; and he
rendered justice to Halley by recogniz-
ing him as the first who had discovered
the true magnetic attraction of the globe.
Hansteen, with the material at his com-
mand, went however a step further, and
computed both the geographical posi-
tions and the probable period of the
revolution of this dual system of poles
or points of attraction round the terres-
trial pole. From these computations he
found that the North American point or
pole required 1,740 years to complete its
grand circle round the terrestrial pole,
the Siberian 860 years; the pole in the
Antarctic regions south of Australia,
4,609 years; and a secondary pole near
Cape Horn, 1,304 years. The influence
of these laborious investigations on the
minds of subsequent inquirers may easily
be imagined.
The matured views of Sir Edward
Sabine on the secular changes — enun-
ciated in the clearest manner in 1864-72
-are deserving of the highest considera-
tion. An ardent admirer of the genius
and no less of the sagacity of Halley, he
in part follows Halley's views, and con-
siders that two magnetic systems are
directly recognisable in the phenomena
of the magnetism of the globe; the one
having a terrestrial, the other a cosmical
origin. The magnetism proper of the
globe, with its point of greatest attrac-
tion {i.e. in the northern hemisphere) in
the north of the American continent is
the stronger; the weaker system, or that
which results from the magnetism in-
duced in the earth by cosmical action,
with its point of greatest attraction is,
at present, in the north of the Asiatic
continent. Sir Edward Sabine also ex-
presses his belief that " it is the latter of
these two systems which by its progress-
ive translation, gives rise to the pheno-
mena of secular change, and to those
magnetical cycles which owe their origin
to the operation of the secular change."
Reviewing these several hypotheses
by the light of observations made in
recent years, it is difficult, and indeed in
some directions, impossible to recognise
their accordance with changes now going
on; there can be no doubt, notwithstand-
ing, that Halley and Hansteen analyzed
their facts with skill, and that their
deductions were borne out by those
facts. In explanation of this auomaly
it is necessary to glance retrospectively
on the changes in progress at the times
in which these philosophers gave utter-
ance to their views [1700-1819]. Dur-
ing this long interval, and, so far as re-
lates to parts of the northern hemi-
sphere, for a century before, there was
in the higher latitudes a general move-
ment of the north end of the needle in
the following directions:
Over all that area (embracing the
Atlantic and Indian Oceans) from Hud-
son's Bay to about the meridian of the
North Cape of Europe, and from Cape
Horn to about the western part of
Australia, the north end of the needle
was successively drawn to the west at a
maximum rate of 8' or 10' a year. From
the meridian of the North Cape of
Europe to that of 130° east, it was
successively drawn to the east, while
from thence to Hudson's Bay it was
nearly stationary, or perhaps oscillated a
little; in the southern hemisphere, from
about the western part of Australia to
Cape Horn, the movement was through-
out to the east at the maximum rate of
7' a year. There was thus a general
uniformity of movement; in that hemi-
sphere (dividing the globe into eastern
and western hemispheres) which includes
the Atlantic and Indian Oceans, the
needle was constantly drawn more and
more to the west; in the hemisphere
232
VAN NOSTRAND7 S ENGINEERING MAGAZINE.
embracing the Pacific Ocean, more and
more to the east.
So far then to the early part of the
present century we can trace a harmo-
nious movement of the needle over the
whole globe, justifying the conclusions
of our old philosophers; but in the year
1818 at London, and generally contempo-
raneous with that epoch throughout
Europe and North Africa, the westerly
progress of the north end of the needle
ceased, and an easterly movement com-
menced; this continues to the present
time, and with a yearly increasing rate.
But in the South Atlantic during this
period the westerly movement has never
ceased; it is still going on, and in some
parts with rapidity. Here, then, is a
marked dislocation of the harmonious
regularity embodied in Halley's and
Hansteen's calculations and conceptions.
The matured views of Sir Edward
Sabine, to which I have drawn attention,
seem to anticipate the difficulties attend-
ant on this new and complex movement;
for, if I apprehend his meaning correctly,
they imply that the poles of attraction
which have a terrestrial source, i.e. the
'magnetic poles, are not subject to trans-
lation.*
The hypothesis, if further followed,
is nevertheless beset with difficulties; for
we can scarcely conceive changes due to
cosmical action to be otherwise than
general in character, and to affect the
whole globe. Thus, if the progressive
translation of the induced or weaker sys-
tem in Northern Asia— and presumably
of that in the southern hemisphere —
were the direct causes of the secular
charges, we should anticipate uniformity
in the general movements of the needle
as manifested by its variation and dip
over the earth's surface. But this is
contrary to modern experience; for in
some regions great activity of move-
ment, both in the direction of pointing
and in the inclination of the needle, is
going on; in others there is comparative
repose in both elements; while in another
region the needle remains nearly con-
stant in its direction, while its inclina-
tion sensibly varies from year to year.
For example:
A region of remarkable activity pre-
* So far as modern observations bear on the position
of the magnetic poles, they indicate permanency rather
than change of place.
sents itself in the South Atlantic Ocean;
a great part of the seaboard of South
America extending to Cape Horn, and
including St. Paul's Rocks, Ascension,
St. Helena, and the Falkland Islands,
with their adjacent seas, are embraced
therein. In some parts of this area the
westerly movement of the needle exceeds
7' or 8' a year, and has so progressed
for nearly three centuries. On the
American coast the dip of the south end
of the needle decreases from 7.5' to 4'
yearly, while from the Cape of Good
Hope to Ascension it increases from hr
to 10' yearly. We have here, within
narrow limits, a noteworthy dislocation
of the observed phenomena.
Another region of activity, so far as
is denoted by the changes of variation,
extends over Europe, Western Asia, and
North Africa. Here the needle, in oppo-
sition to the protracted westerly move-
ment going on in the South Atlantic,
commenced moving to the eastward in
the early part of this century; it has a
progressive rate which in some parts
now amounts to 10' a year. The dip
diminishes in this region seldom more
than 3' a year.
A region of activity, so far as the
dip is concerned, but with little change
in the variation, is to be found on the
west coast of South America; at Val-
paraiso, as at the Falkland Islands, the
south dip decreases at the rate of 7'
yearly, but in sailing northward and
reaching the 10th degree of south lati-
tude, this active movement appears to
cease.
But little activity in either element
now exists over the habitable part of the
North American continent or in the
West Indies. Throughout China there
is little change in the variation, but an
increasing dip of 3' or 4', and thus a
reverse movement to that going on in
Europe.
Over a great part of the Western
Pacific Ocean, as also in Australia and
New Zealand, there is so little change
in the two elements that this may be
termed a region of comparative repose.
These are a few facts relating to
secular changes going on in two mag-
netic elements within our own time;
and what are the inferences to be drawn
therefrom ? They appear to me to lead
to the conclusion that movements, cer-
CHANGES IN THE EARTH'S MAGNETISM.
233
tainly beyond our present conception,
are going on in the interior of the earth;
and that so far as the evidence presents
itself, secular changes are due to these
movements and not to external causes;
we are thus led back to Halley's con-
ception of an internal nucleus or inner
globe, itself a magnet, rotating within
the outer magnetised shell of the earth.
We need not here pause to discuss
the probability of this fanciful conception
of the old philosopher, but proceed to
examine how far the behavior of another
element, the intensity of the earth's
magnetism, confirms the view that move-
ments are going on in the interior of our
globe. In common I believe with all
those who have pursued the study of
this element, from the time when Sabine's
original memoir to the British Associa-
tion (1837) threw so much light on this
special division of the subject, I had
conceived that stability, within very
limited conditions, was a distinctive con-
dition of the earth's force; and that it
was alone by watchful attention to the
instruments of precision devised for its
determination that changes in short in-
tervals of time, such as a generation,
could be detected.* If we turn to the
results obtained in this country through
nearly half a century, it is possible that
an increase of two or three hundredths
of the total force may be found. In
Italy at the present time the annual
decrease has been given by that active
observer, the Rev. Father Perry, as .004;
so also on the North American continent,
where, as we are told by the zealous
magnetician, Schott, there is evidence of
the force slightly increasing at Washing-
ton, of being stationary at Toronto, in
Canada, and slightly decreasing at Key
West, in the Gulf of Mexico. So far
stability, within very small limits, obtains
over a very large part of the northern
hemisphere. If, however, we turn to the
continent of South America and its
adjacent seas (parts of which are regions
of marked activity as denoted by changes
in the variation and dip of the needle),
we shall find a diminution of the intensi-
* The investigations of that able magnetician, Mr.
Broun, led him to consider that the earth's magnetic
force increases and diminishes from day to day by nearly
the same amount over the whole globe. These increases
and diminutions have been traced to the action of the sun
in such a way that the greatest of them recur f requently
at intervals of twenty-six days, or multiple- of twenty-six
days— a period attributable to the sun's rotation.
ty of the earth's force now going on in
a remarkable degree; an examination of
the recent observations made by the
Challenger }s officers at Valparaiso and
Monte Video, compared with those made
by preceding observers, show that within
half a century the whole force had re-
spectively diminished one-sixth and one-
seventh — at the Falkland Islands one-
ninth. Farther north we find at Bahia
and Ascension Island, in the same period
of time, an equally marked diminution
of one-ninth of the force. This area of
diminishing force has wide limits; it
would appear to reach the equator and
to approach Tahiti on the west and St.
Helena on the east; at the Cape of Good
Hope there is evidence of the force
increasing.
Such are the facts, and how are we
to interpret them ? Whichever way we
look at the subject of the earth's mag-
netism and its secular changes, we find
marvelous complexity and mystery ;
lapse of time and increase of knowledge
appear to have thrown us farther and
farther back in the solution. The terella
of Halley, the revolving poles of Han-
steen, and the more recent hypotheses of
the ablest men of the day, all fail to
solve the mystery. We must not, how-
ever, be discouraged at these repulses in
the great conflict for the advancement
of human knowledge. The present cen-
tury has been productive of keen ex-
plorers in the field of terrestrial mag-
netism; others emulous of fame are
pressing rapidly from the rear, and
knowing as we do that knowledge shall
be increased, we may confidently antici-
pate the day when this, one of Nature's
most formidable secrets, shall be re-
vealed.
The telephone has been adopted on
the mountain section of the Central
Pacific Railway. The points supplied
are Truckee, Blue Canon, Summit, Cas-
cade, Strong's Canon, Yuba Pass, Tama-
rack, and Camp 3, The main office is
at Blue Canon, and each track-walker is
compelled to report himself both in pass-
ing east and west. The telephones are
to be placed at distances of a very few
miles apart, to enable the " track-
walkers," or platelayers, to make any
necessary requests or other communica-
tions, as to state of road.
234
VAN NOSTRAJSirS ENGINEERING MAGAZINE.
THE THEORY OF INTERNAL STRESS IN GRAPHICAL
STATICS.
Bt HENRY T. EDDY, C. E., Ph. D., University of Cincinnati.
Written for Van Nostrand's Magazine.
III.
COMBINATION AND SEPARATION OF STATES
OF STRESS.
Problem 19.— When two given states
of right shearing stress act at the same
point, and their principal stresses have a
given inclination to each other, to com-
bine these states of stress and find the
resultant state.
In Fig. 12 let oxx, ox2 denote the di-
rections of the two given principal -f-
stresses, and let ax = o?ix, a^=on2 repre-
sent the position and magnitude of these
principal stresses. Since the given
stresses are right shearing stresses
ax = — bx, a2= — b2 and the respective
planes of shear bisect the angles between
the principal stresses. Now it has been
previously shown that the intensity of
the stress caused by the principal stresses
ax = —bx is the same on every plane
traversing o: the same is true of the
principal stresses aa=— -59 : hence, when
combined, they together produce a stress
of the same intensity on every plane
traversing o. This resultant state of
stress evidently does not cause a normal
stress on every plane, hence the result-
ant state must be a right shearing stress.
Let us find its intensity as follows :
The principal stresses a1=—bl cause a
stress onx on the plane yxy^ and the princi-
pal stresses a^=—b^ cause a stress om, on
the same plane in such a direction that
aj,owi2 =a,1o#a, as has been before shown.
Complete the parallelogram n^om^r^/
then or2 represents the intensity and di-
rection of the stress on yxyx. But the
principal stresses bisect the angles be-
tween the normal and the resultant in-
tensity, therefore, ox, which bisects
xxor^ is the direction of a principal stress
of the resultant state, and or=ori=a is
the intensity of the resultant stress on
any plane through o.
The same result is obtained by finding
the stress the plane y2y„ in which case
we have on^ = a2 acting normal to the
plane, and omx=.a^ in such a direction
that xxomx=x^oxx. The sides and angles
of n2o?nxrx and nxom^r2 are evidently
equal, hence the resultants are the same,
or1 = o?\=a, and ox bisects x2orx.
The algebraic solution of the problem
is expressed by the equation,
c?=ax + a* + 2aj«2 cos 2 xxx.x,
from which a may be found, and, finally,
the position of or is found from the pro-
portion,
sin 2xxx : a2 \ \ sin 2xx2 : ax \ \ sin 2xxx<i : a.
Problem 20. — When any two states
of stress, defined by their principal
stresses, act at the same point, and their
principal stresses have a given inclina-
tion to each other, to combine these
states and find the resultant state.
Let ax, bx
and tf2, b„
be the given prin-
cipal stresses, of which at and a2 have
the same sign and are inclined at a
known angle xxx^ but in so taking ax
and <72 they may not both be numerically
greater than bx and b2 respectively.
Separate the pair of principal stresses
axbx into the fluid stress + ^{ax + bx), and
the right shearing stress dz$(ax — bx) as
INTERNAL STRESS IN GRAPHICAL STATICS.
235
has been previously done; and in a simi-
lar manner the principal stresses a2 52
into +iK + #2) a.nd +iK — h)- Then
the combined fluid stresses produce a
fluid stress of + %(cix + bx + a^ + b^) on
every plane through o; and the com-
bined right shearing stresses cause a
stress whose intensity and position can
be found by Problem 19.
The total stress is obtained by com-
bining the total fluid stress with the re-
sultant right shearing stress.
Of course, any greater number of
states of stress than two, can be com-
bined by this problem by combining the
resultant of two states with a third state
and so on.
The algebraic expression of the com-
bination of any two states of stress is as
follows :
(a + b) = (al + b1 + ai + b2),
+ 2{ax — bx) (tf2— 6J cos 2x1xii
.-. a^i^ + ^ + a^b^Ka^Y
+ (a-bJi + 2(arb1)(a-b2)cos 2xxzJA),
*=i(«, + ^ + «, + ^-[(vA)' + to--^*
+ 2(ax-bx)(a^-bJcos 2xxxJ^)i
in which a and b are the resultant prin-
cipal stresses. Also, sin 2xxx: a^—b^
: : sin 2xx<i: a1 — b1 : : sin 2aJ1«2: a — b.
Problem 21. — In a state of stress
defined by the stresses upon two planes
at right angles to each other, to find the
principal stresses.
Let the given stresses be resolved into
tangential and normal components; it
has been shown that the tangential com-
ponents upon these planes are of equal
intensity and unlike sign. Let the in-
tensity of the tangential component be
at, and that of the normal components
aH and bn respectively. The tangential
components together constitute a state
of right shearing stress of which the
given planes are the planes of shear,
and the principal stresses bisect the
angles between the given planes.
Separate the remaining state of stress
into the fluid stress +i(an + bn) and
the right shearing stress ±\(an — bn),
and combine this last right shearing
stress with that due to the tangential
components. The final result is found,
just as in Problem 20, by combining the
fluid stress \(an -f bn) with the resulting
right shearing stress.
This problem can also be solved in a
manner similar to that employed in
Problem 6.
The result is expressed by the equa-
tions,
a + b=an -f- bn,
(a-^)a=(an-5n)2 + 4^*
for the angle which has been heretofore
denoted by xxx^ is in this case 45° .*. cos
2a:1a;2=0
.-. a=±(an + bn + [(an - bnY + WW
b=i{an + bn ~[(an - bny + 4at*]y>)
sin. 2xxx : 2at : : sin. 2xx<l : an — bn
: : 1 : a—b9
but 2xx1 = 90° — 2xxi ,
.*. tan 2^ = 26^ ~ (an — bn).
Problem 22. — In a state of stress
defined by two simple stresses which act
at the same point and have a given
inclination to each other, to combine
them and find the resultant state.
It has been previously mentioned that
any simple stress as ax can be separated
into the fluid stress + \ax and the right
shearing stress ±Ja„ as it is simply a
case in which bx = 0. Hence the simple
stresses al9 a2 can be combined as a spe-
cial case of Problem 20, in which bx and
62 vanish. The results are expressed
algebraically as follows:
a+b=al + a2,
(a — by=a* + a* + 2a1ai cos 2x1xii
.-. ab=^axa^(l — cos 2xxx^)
.-. ab=axaCi sin'a^a;,.
Since a simple compression or tension
produces a simple stress in material, this
problem is one of frequent occurrence,
for it treats the superposition of two,
and hence of any number of simple
stresses lying in the same plane.
This problem is of such importance
that we think it useful to call attention
to another solution of it, suggested by
the algebraic expressions just found.
In Fig. 13 let
o'a' — ax, o'b' — a^ .'. o,r/=Vala^ = oi.
Now, if oir=x1x3, then or=o'rr sin xfa
.-. or^ — oa'.ob'^o'a'.o'b' sin'^aj,
,\ oa' = a and ob' = b.
236
VAN NOSTRAND'S ENGINEERING MAGAZINE.
i
1
v
^^\Fig. 13
/
\
/
f
\
\
I
y
<
y
I
This solution is treated more fully in
Problem 23.
Problem 23. — When a state of stress
is defined by its principal stresses, it is
required to separate it into two simple
stresses having a given inclination to
each other.
It was shown in Problem 22 that
a + b=a1 + a„ and ab=a1a2 sin xxx2.
Let us apply these equations in Fig.
13 to effect the required construction.
Make oaf = a, ob' = b; then a'b' = al-\-a2.
At o erect a perpendicular to a'b' cut-
ting the circle of which a'b' is the dia-
meter at r\ then or*=ab, the product of
the principal stresses. Also make a'oi
=x1xa the given inclination of the sim-
ple stresses, and let- ri \\ a'b' intersect oi
at
; then or=oi sin xxx^ .'. oi
Make oj—oi and draw jr' \\ a'b', then
o'r' = oi, and ofa'.o'b'=o'rrii
V o'a' = a1 and o'b,=a,li
the required simple stresses. This con-
struction applies equally whether the
given principal stresses are of like or
unlike sign, and also equally whether
the two simple stresses are required to
have like or unlike signs.
Problem 24. — When a state of stress
is defined by its principal stresses, to
find the inclination of two given simple
stresses into which it can be separated.
In Fig. 13 let oa'=a, ob'=b be the
intensities of the principal stresses, and
o'af = a1, o'b'=a2 be the intensities of the
given simple stresses. It has been
already shown that a + b=a1 + ai. Draw
the two perpendiculars or and oV;
through r draw ?°i\\a'b'; make oi=oj
= o'r'; then is oir=ioaf the required
inclination, for it is such that
ab=axa2 sin'a;^
Problem 25. — To separate a state of
right shearing stress of given intensity
into two component states of right shear-
ing stress whose intensities are given, and
to find the mutual inclination of the
principal stresses of the component
states.
In Fig. 12, about the center o, describe
circles with radii 07iY — at, on2=a„ the
given component intensities; and also
about o at a distance or^a, the given
intensity. Also describe circles with radii
rjn^—on^ r1n^=on1 cutting the first
mentioned circles at m, and n2: then is
l^owij^a;^ the required mutual inclina-
tion of the principal stresses of the com-
ponent states. This is evident from
considerations previously adduced in con-
nection with this figure. The relative
position of the principal stresses and
principal component stresses is also read-
ily found from the figure.
Problem 26. — In a state of right
shearing stress of given intensity to sep-
arate it into two component states of
right shearing stress, when the intensity
of one of these components is given and
also the mutual inclination of the princi-
pal stresses of the component states.
In Fig. 12, about the center o describe
a circle rr with radius or—af the inten-
sity of the given right shearing stress,
and at nl7 at a distance* onx = ax from o
which is the intensity of the given com-
ponent, make x1?i1rz=2x1x2, twice the
given mutual inclination ; then is nlri
the distance from n, to the circle rr the
intensity of the required component
stress. The figure can be completed as
was done previously.
It is evident, when the component ax
exceed «, that there is a certain maxi-
mum value of the double inclination,
which can be obtained by drawing wtr9
tangent to the circle rr, and the given in-
clination is subject to this restriction.
Other problems concerning the com-
bination and separation of states of
stress can be readily solved by methods
like those already employed, for such
problems can be made to depend on the
combination and separation of the fluid
stresses and right shearing stresses into
which every state of stress can be sep-
arated.
INTERNAL STRESS IN GRAPHICAL STATICS,
237
PROPERTIES OF SOLID STRESS.
We shall call that state of stress at a
point a solid sti^ess which causes a stress
on every plane traversing the point. In
the foregoing discussion of plane stress
no mention was made of a stress on the
plane of the paper, to which the plane
stress was assumed to be parallel. It is,
evidently, possible to combine a simple
stress perpendicular to the plane of the
paper with any of the states of stress
heretofore treated without changing the
stress on any plane perpendicular to the
paper.
Hence in treating plane stress we have
already treated those cases of solid stress
which are produced by a plane stress
combined with any stress perpendicular
to its plane, acting on planes also per-
pendicular to the plane of the paper.
We now wish to treat solid stress in a
somewhat more general manner, but as
most practical cases are included in plane
stress, and the difficulties in the treat-
ment of solid stress are much greater
than those of plane stress, we shall make
a much less extensive investigation of its
properties.
Conjugate Stresses. — Let xx, yy, zz
be any three lines through o; now, if
any state of stress whatever exists at o,
and xx be the direction of the stress on
the plane yoz, and yy that on zox, then
is zz the direction of the stress on xoy :
i.e., each of these three stresses lies in
the intersection of the planes of action of
the other two.
Reasoning like that employed in con-
nection with Fig. 1, shows that no other
direction than that stated could cause
internal equilibrium; but a state of stress
is a state of equilibrium, hence follows
the truth of the above statement.
Tangential Components. — Let xx,
yy, zz be rectangular axes through o ;
then, whatever may be the state of stress
at o, the tangential components along xx
and yy are equal, as also are those along
yy and zz, as well as those along zz and
xx.
The truth of this statement flows at
once from the proof given in connection
with Fig. 3.
It should be noticed that the total
shear on any plane xoy, for example, is
the resultant of the two tangential com-
ponents which are along xx and yy re-
spectively.
State of Stress. — Any state of solid
stress at o is completely defined, so that
the intensity and direction of the stress
on any plane traversing o can be com-
pletely determined, when the stresses on
any three planes traversing o are given
in magnitude and direction.
This truth appears by reasoning simi-
lar to that employed with Fig. 4, for the
three given planes with the fourth en-
close a tetrahedron, and the total dis-
tributed force acting against the fourth
plane is in equilibrium with the resultant
of the forces acting on the first three.
Principal Stresses. — In any state of
solid stress there is one set of three con-
jugate stresses at right angles to each
other, i.e. there are three planes at right
angles on which the stresses are normal
only.
Since the direction of the stress on any
plane traversing a given point o can
only change gradually, as the plane
through o changes in direction, it is
evident from the directions of the
stresses on conjugate planes that there
must be at least one plane through o on
which the stress is normal to the plane.
Take that plane as the plane of the
paper; then, as proved in plane stresses,
there are two more principal stresses
lying in the plane of the paper, for the
stress normal to the plane of the paper
has no component on any plane also
perpendicular to the paper.
Fluid Stress. — Let the stresses on
three rectangular planes through o be
normal stresses of equal intensity and
like sign; then the stress on any plane
through o is also normal of the same in-
tensity and same sign.
This is seen to be true when we com-
bine with the stresses already acting in
Fig. 5, another stress of the same inten-
sity normal to the plane of the paper.
Right Shearing Stress.— Let the
stresses on three rectangular planes
through o be normal stresses of equal
238
VAN NOSTRAND'S ENGINEERING MAGAZINE.
intensity, but one of them, say the one
along xx, of sign unlike that of the other
two; then the stress on any plane through
o, whose normal is x'x' , is of the same
intensity and lies in the plane xox' in
such a direction rr that xx and the plane
yz bisect the angles in the plane xox' be-
tween rr and its plane of action, and
rox' respectively.
The stress parallel to yz is a plane
fluid stress, and causes therefore a normal
stress on the plane xox'. Hence the re-
sultant stress is in the direction stated,
as was proved in Fig. 6.
Component States of Stress. — Any
state of solid stress, defined by its prin-
cipal stresses abc along the rectanglar
axes of xyz respectively, is equivalent to
the combination of three fluid stresses,
as follows:
\{a -f b) along x and y, — \ (a -f b) along z ;
%(c + a) along z and x,— \{c + a) along y;
i(b + c) along y and z,— %(b + c) along y;
For these together give rise to the fol-
lowing combination:
i(a + b)+i(c + a)— \{b + c) = a, along a;
i(a + b)— i(c + a)-rl(b + c) = b, along y;
i(a + b)+%(c + a)+{(b + c) = c, along x.
In case b=0 and c—0 this is a simple
stress along x.
Component Stresses. — Any state of
solid stress defined by its principal
stresses can also be separated into a fluid
stress and three right shearing stresses,
as follows:
i{a + b + c) along x, y, z;
%(a—b — c) along x, and
~i(a -b — c) along y and z;
\{b—c—a) along y, and
— \{b — c—a) along z and x ;
\{c — a—b) along z, and
— \{c— a— b) along x and y ;
It will be seen that the total stresses
along xyz are abc respectively. This
system of component stresses is remarka-
ble because it is strictly analagous in its
geometric relationships to the trammel
method used in plain stress. We shall
simply state this relationship without
proof, as we shall not use its properties
in our construction.
If the distances 2^o:x = a, pbx = b, pct=c
be laid off along a straight line from the
pointy, and then this straight be moved
so that the points ax bx cx move respec-
tively in the planes yz, zx, xy ; thenjt>
will describe an ellipsoid, as is well
known, whose principal semiaxes are
along xyz, and are abc respectively.
Now the distances pax, pbx, pcx, may be
laid off in the same direction from p or
in different directions; so that, in all,
four different combinations can be made,
either of which will describe the same
ellipsoid. But the position of these
four generating lines through any as-
sumed point xJylz1 of the ellipsoid is such
that their equations are
a b . c .
—(*-*,) = ±- (y-yj= ±-(«-2t)
Now if the fluid stress i(a + b + c) = orl
be laid off along the normal to any plane,
i.e. parallel to that generating line which
in the above equation has all its signs
positive, and the other three right shear-
ing stresses rx?\, r2r3, r3r4 be laid off
successively parallel to the other generat-
ing lines, as was done in plane stresses,
the line ort will be the resultant stress on
the plane.
problems in solid stress.
Problem 21. — In any state of stress
defined by the stresses on three rectangu-
lar planes, to find the stress on any given
plane.
Let the intensities of the normal com-
ponents along x y z be an bn cn respect-
ively, and the intensities of the pairs of
tangential components which lie in the
planes which intersect in x y z and are
perpendicular to those axes be at bt ^re-
spectively, e.g., at is the intensity of the
tangential component on xoy along y, or
its equal on xoz along z.
In Fig. 14 let a plane parallel to the
given plane cut the axes at xxyxzx; then
the total forces on the area xxyxzx along
xyz are respectively :
xxyxzx.ax=yxozx . an + xxoyx . bt + zxoxt.ct
xxyxzx.bx=yxozx . ct. -f- xxoyx . at -f- zxoxx.bn
xxyxzx.cx-=yxozx . bt -f x pyx . cn + zxoxx.at
in which a1blcx are the intensities of the
INTERNAL STRESS IN GRAPHICAL STATICS.
239
components of the stress on the plane
xxyxzx along xyz respectively. Now
yxozx-?-xxyxzx — cos xn
zxoxx-±-xxyxzx = co& yn
xxoyx-^x xyxzx = cos zn.
.'. ax = On cos xn + bt • cos zn + ct cos yn
bx=ct cos xn + at . cos zn + bn cos y?i
Cj = bt cos jm + c» . cos zn + a* cos yn
and r'rra^ + ^ + Cj3, therefore the result-
ant stress r is the diagonal of the right
parallelopiped whose edges are axbxcx.
In order to construct axbxcx it is only-
necessary to lay off an bn cn> at bt ct along
the normal, and take the sums of such
projections along xyz as are indicated in
the above values of axbxcx.
Thus, in Fig. 14, let xxyxzx be the
traces of a plane, and it is required to
construct the stress upon a plane parallel
to it through o.
The ground line between the planes of
xoy and xoz is ox. The planes xoz and
yoz on being revolved about ox and oy
respectively, as in ordinary descriptive
geometry, leave oz in two revolved posi-
tions at right angles to each other.
The three projections of the normal
at o to the given plane are, as is well
known, perpendicular to the traces of the
given plane, and they are so represented.
Let oaz be the projection of the normal
on xoy, and oay that on xoz. To find
the true length of the normal, revolve it
about one projection, say about oaz, and
if az an = tf2 ay then is oan the revolved
position of the normal.
Upon the normal let oan = ant obn =
bn, ocn = cn} the given normal compo-
nents of the stresses upon the rectangu-
lar planes, aud also let oat=att obt = bt,
oct = ct, the given tangential compo-
nents upon the same planes.
Let afi^c^ a2'b./c2' be the respective
projections of the points an bn cn, at bt ct
of the normal upon the plane xoy by
lines parallel to oz, similarly ay> etc., are
projections by parallels to oy, and ax' ,
etc., by parallels to ox.
We have taken the stresses cn and ct of
different sign from the others, aud so
have called them negative and the others
positive.
It is readily seen that the first of the
above equations is constructed as fol-
lows:
cz'c'
ax = oax = oa2 +
the other two equations
be-
Similarly,
come:
b=ob= — oc^ + at a2' + ob.2
cx=oc=a\' —czct + oa2
We have thus found the coordinates
of the extremity r of the stress or upon
the given plane; hence its projections
240
VAN NOSTKAND'S ENGINEERING MAGAZINE.
upon the planes of refererence are re-
spectively orX} orPi orz.
Problem 28. — In any state of stress
denned by its three principal stresses,
to find the stress on any given plane.
This problem is the special case of
Problem 27, in which the tangential com-
ponents are each zero. Taking the nor-
mal components given in Fig. 14 as
principal stresses we find oa^=anGOS xn,
ob2=bn cos yn9 oc2=cn cos zn, as the co-
ordinates which determine the stress or'
upon the given plane, and the projections
of or' are orx\ ory', or/, respectively.
From these results it is easy to show
that the sum of the normal components
of the stresses on any three planes is
constant and equal to the sum of the
principal stresses. This is a general
property of solid stress in addition to
those previously stated.
Problem 29.— Any state of stress be-
ing defined by given simple stresses, to
find the stresses on three planes at right
angles to each other.
In Fig. 14 let a simple stress act along
the normal to the plane xxyxzx, and cause
a stress on that plane whose intensity is
an = oan, then is ancos %n=oa2 the in-
tensity of the stress in the same direction
acting on the plane yoz. The normal
component of this latter intensity is
ancos2m=oa2. cos xn=oas,
and it is obtained by making oaj — oa^
a/az" || xryx, and az"az\\oy. The tan-
gential component on yoz is od' in mag-
nitude and direction, and it is obtained
thus: make az"d=az"a2', then in the
right angled triangle dasa2'' \ da% is the
magnitude of the tangential component;
now make odf=da2. This tangential
component can be resolved along the
axes of y and z. The stress on the
planes zox and xoy can be found in simi-
lar manner, since the tangential compon-
ents which act on two planes at right
angles to each other and in a direction
perpendicular to their intersection are,
as has been shown, equal; the complete
construction will itself afford a test of its
accuracy.
Other simple stresses may be treated in
the same manner, and the resultant stress
on either of the three planes, due to these
simple stresses, is found by combining
together the components which act on
that plane due to each of the simple
stresses.
It is useless to make the complete
combination. It is sufficient to take the
algebraic sum of the normal components
acting on the plane, and then the alge-
braic sum of the tangential components
along two directions in the plane which
are at right angles, as along y and z in
yoz.
The treatment of conjugate stresses in
general appears to be too complicated to
be practically useful, and we shall not
at present construct the problems arising
in its treatment.
A FEW NOTES ON METHODS OF BUILDING, AND MANU-
FACTURE OF MATERIALS, IN INDIA.
Bt AN ASSISTANT ENGINEER, D.P.W., PUNJAB.
From " The Builder."
Materials, their uses and manufac-
ture, are often so different in India to
those of Europe that it may possibly
interest some of our readers to know the
various kinds and values of timber; the
method of manufacture of bricks and
lime (generally very primitive), and
other materials in use; and to know the
many difficulties an engineer has to over-
come, which arise purely from the
scattered work he has to do, the scanty
population (in many places) and means
of transport, and other obstacles of an
equally minute character.
This article does not aim at going very
deeply into the subject, as those who
wish to study the matter more closely
cannot do better than by consulting
" The Roorkee Treatise on Indian Civil
Engineering," a book full of practical
suggestions and descriptions of the uses
and manufacture of materials, &c, in the
BUILDING AND MANUFACTURE OF MATERIALS IN INDIA.
241
Bengal Presidency, besides the " Theory
of Engineering," for which it is used as
a text-book for the Roorkee College
students.
BUILDINGS.
Stone. — The usual material is brick in
the plains, and stone in the hills. It is
only where stone is available on the spot
that it can compete with brick, as the
expense of carriage across unbridged
torrent beds, and over unmetalled roads,
is almost always a bar to its use in any
but ornamental work. The red sand-
stones of the Salt Range, Delhi, and
Jaipur, it is true, are carried a long way,
but their use is confined to ornament
alone, or to pavements of public build-
ings, and then only sparingly. The
stone is all, or nearly all, sandstone, and
generally good — in many places very
good, and hard, but in others it is very
poor, rotten, and worthless, except to be
pounded up and mixed with lime.
Granite is not found anywhere in the
Punjab; neither is limestone used, ex-
cept in the form of boulders for irriga-
tion dams, &c, where massive work is
required. In this form it has been ex-
tensively used at Madhopur, the head
works of the Bair Doab Canal, where a
dam across the Rair has been construct-
ed, to drive the waters of that river, as
they debouch from the hills, into the
main canal. During the unprecedented
floods of August and September, 1875,
this enormous piece of work was under-
mined, and turned in many places com-
pletely topsy-turvey, giving ample evi-
dence of the force of the waters, which
at other places have spread ruin and
desolation over the low grounds of the
province.
Bricks. — The next material for the
walls of houses of the better class is
brick — " pucca " brick, as it is called, the
word " pucca " meaning thorough, good,
in contradistinction to "kucha," which
. means exactly the reverse, and is applied
to sun-dried or unburnt bricks. The
third or intermediate class is called
" peela," and is applied to partially-
burnt bricks on account of their color,
" peela" being used for an ochre color,
just such a one as an underburnt brick
would have. All three kinds are used in
different qualities of work, and in a dry
climate, such as India, it is wonderful
Vol. XIX.— No. 3—16
what a length of time an underburnt
brick wall will last when properly pro-
tected with mud and straw plaster.
Bricks are of all sizes; the old native
brick was about 8 inches X 4 inches,
and from 1 inch to 1^ inches thick.
These are in some places called " Akbare,"
possibly they were most common during
the reign of Akbar (a.d. 1556-1605),
under whom a large amount of work
was commenced and partly completed.
The native brick in common use now is
called Lahore, and is about 5 inches X
3 inches X 1 inch. It makes very good
strong work, but, as may be supposed,
uses a good deal of mortar.
The bricks in use in the Department
of Public Works and Railways are the
English stock, 9 inches by 4^- inches X
2^ inches or 3 inches; the irrigation
brick, which is 10 inches X 5 inches X
2 J inches; and the large brick, 12 inches
X 6 inches X 2£ inches to three inches.
Kilns. — The old native kiln or " Pa-
jarvah " is a very cheap though slow
style of kiln, and the bricks have one ad-
vantage over flame kilns — they are thor-
oughly annealed. The kiln is V-shaped
in plan, an excavation begun in the
ground, and at a depth of 2 feet or 3
feet, is continued at an angle of about 1
in 10, until it merges into an embank-
ment formed of the earth excavated.
When these kilns were first started their
dimensions were not very large possibly,
but in many kilns -whose lives vary from
20 to 150 years, the excavation at the
toe of the V is from 3 feet to 10 feet
above the surface of the ground.
The material used is brushwood, and
horse or cattle litter, the solid refuse of
the cities, <fcc. The method of loading is
as follows : — A layer of light brushwood
is laid at the bottom of the kiln, and
covered with "oopla," or cow-dung
cakes dried in the sun, leveled with lit-
ter, then a layer of bricks, two courses
on edge of 9 inch bricks, or three of
native bricks, and these are covered with
litter double the thickness of brick below
and damped down with ashes. This
goes on until the loading has reached
about 12 feet from toe of kiln, where, by
the way, the firing begins. The courses
of brick are here increased to three, and
then four, and at a little distance two
tiers of brick and litter are laid, and so
on until the kiln is loaded well away
242
VAN nostkand's engineering magazine.
from toe; it is then fired. The kiln is
always so placed as to face the prevail-
ing wind, and when lit, the fire is driven
forward by the wind. The kiln is set
alight by igniting the brushwood at the
mouth, and by damping down any place
where the fire might burst out too freely,
with ashes, the flame is kept in check.
The loading proceeds, and as soon as the
bricks near the mouth are cool, unloading
the kiln is commenced, and in this way
unloading is going on at the mouth,
firing in the center, and loading towards
the end. A large "Pajarvah," 50 feet
long, will contain an equivalent to 300,-
000 of 9 inch bricks, and will take seven
or eight months loading and unloading.
The " Clamps" present additional
facilities for unloading. They vary in
size, from the one which contains 20,000
bricks (9 inch size), to the large one
which contains 150,000. The fuel is
"oopla" (dry cow-dung cakes, about
8 inches diameter and conical, 3 inches
or 4 inches or 5 inches in height). The
loading is horizontal, with a perceptible
dip towards the center. The proportions
of fuel are : 1st layer, 2 of fuel to f
brick; 2d or 3d layer, 2 to 1; and above
that less and less, until near the top it is
lj to 1. A small kiln will turn out
bricks in three weeks from firing, and a
large one in six weeks. Bricks burnt in
litter kilns do not burn so deep a red as
those from flame-kilns; they are much
harder and better annealed, but they
contain more ammonia and discolor much
sooner. Clamps are very useful in burn-
ing ornamental brick, as the heating and
cooling process is so gradual that the
fine edges or mouldings are very little
injured.
Flame-kilns. — There are a good many
varieties of flame-kilns; one or two suc-
cessful patents have been, within the
last four or five years, obtained for their
use. The best kiln of the old kind is
called the "Lind" kiln, and is about 26
feet by 18 feet, inside measurement, and
12 feet high above the arches. An excava-
tion in the ground, 7 feet in depth, con-
tains the furnace, the same size as the
kiln, but divided into two by a wall in
the furnace. There are parallel walls 5
inches or 6 inches apart, carried on
arches, on which the bricks to be burnt
rest. In this kind of kiln large and
small wood can be burnt together, even
large logs of 1 cwt. to 2 cwt. When
properly loaded and fired, the loading
occupies two days' firing, 70 to 80 hours,,
according to season of year. The bricks
cool in 25 days, and give an out-turn of
88 to 94 per cent. Each kiln contains
44,000 to 47,00(1 9-inch bricks.
Other varieties of the same-sized kiln
are used ; in many there are no arches;
the bricks themselves forming arches.
That called the "Allahabad" kiln is
about 100 ft. X 18 X 12. Its method is
rather complicated, and wood, coal, and
charcoal are all used during the process.
It burns a large quantity of bricks at a
time, between 2 and 2^ lakhs, and its
out-turn is said to be very good. Coal
is not -much used in Upper India, and
nowhere above Allahabad, owing to the
great cost of carriage.
The kiln which is best adapted for
large works ist the one known as
" Butt's Annular Kiln; " it is a very sim-
ilar one in theory to Hoffman's, but is
much simpler, and not nearly so costly
to erect. It requires considerable expe-
rience before its full capabilities can be
developed. The coolies in charge must
be all trained men — otherwise it is a fail-
ure. The principle of the kiln is simply
one which may be called "endless."
There are two walls, circular on plan, 12
ft. apart, and having 11 flights of steps,
which serve as buttresses, whilst giving
access to the top. The bricks are loosely
packed in concentric walls, 3 in. or 4 in.
apart, and at every four feet arches are
constructed, exactly opposite the fire-
holes in the external walls. The radius
of the inner wall is 75 ft., and each sec-
tion—^, e., the piece between a flight of
steps— contains 8 holes. The method of
loadmg is peculiar, and not easily under-
stood without a diagram. Suffice it to
say, that four holes are fired with wood
(not over 8 in. diameter) at the same
time, and the smoke is drawn out of
openings left in the loading, about 20 ft.
ahead of the last hole, air being drawn
through the already fired part of the
kiln. By this means the green bricks
are gradually dried, heated, and brought
to a white heat, and as gradually cooled
after they have been burnt, as there is
no escape of heat upward, the top layer
being covered with one ft. of ashes. A
lakh (100,000) of bricks can thus be
burnt with 150 ohms or 5.36 tons of fuel.
BUILDING AND MANUFACTURE OF MATERIALS IN INDIA.
243
A kiln is divided into 12 divisions ; each
division, being about 50 ft, in length,
contains 23,000 9-in. bricks. It follows
that by the time the kiln has been once
fired round 276,000 bricks will have been
burnt ; about 14 to 15 sections can be
fired per mensem. Only about two-
thirds of the kiln is loaded at one time —
say, about 200,000 of bricks ; unloading
goes on at one section, loading a section
or two behind, and firing from half to a
section behind that, so that even though
the loading be interfered with by unsea-
sonable weather, the out-turn can be
depended upon for some weeks. The
kiln described is circular on plan, but it
could, of course, be built elliptically
equally well to suit shape on size of
ground. There is also a Rectangular kiln
on the same principle, but it is not one
much used. Size of ground is not usually
an object of importance as brickfields are,
as a rule, some distance away from can-
tonments or stations, on sanitary grounds.
Underburnt bricks are much used in na-
tive buildings and in partition walls of
2d class buildings, as they stand very
well when not exposed to the atmosphere
or damp. Sun-dried bricks are used in
very large quantities, both in native
buildings and in those built by Govern-
ment for jails, &c, in dry climates.
When properly plastered (mud, chopped
straw, and cowdung) and kept in repair,
the heavy rains have very little effect on
them, but now and then a shower of rain
of long continuance will bring the
houses down as if they were made of
sugar. It is said 8 hours' rain would
not leave such a place as Mooltan.
During the season of 1875 the whole of
the new jail in Amritsur and part of that
in Lahore were completely ruined. Both
were built of sun-dried brick, and both
together represent a loss of some £12,000
to Government. In the author's opinion
sun-dried work for Government build-
ings is quite a mistake, and, though
cheap, is very nasty. It cannot be re-
paired as often as it should be, and, in
the long run, costs a great deal.
Concrete is the material for India.
What this country wants is a good quick-
setting cement like the Portland, and
that it has not as yet got. Bricks being
obtained, the next requisite is
Lime. — Stone lime is obtainable near
the hills, and the average distance from
the places where it is made and its desti-
nation is, in the Punjab, 30 to 50 miles.
It is in many places obtainable only in a
slaked condition. Its cost unslaked
varies from £1 to £4 per ton. It is gen-
erally of a white color, and fat. In fact,
the inferior and more hydraulic qualities
are not much used, as they could bear
less admixture of soorkee, the cheaper
material. The limestone is found in the
bed of hill torrents, and is washed down
from the mountains above. It is never
grained, and the boulders are always
burnt rough just as they are found. The
kilns are V-shaped, and are loaded with
the fuel underneath, and are then left to
burn themselves out. The fuel is the
light brush-wood of the hills burnt quite
green. The result is that only about
half is burnt properly, and each large
lump has a core of imperfectly calcined
stone in its interior, which is pure waste,
as the lime is always purchased by
weight. Fat lime is generally used with
soorkee, which is brick refuse pounded
fine, screened, and then mixed with the
lime in the proportion of 1 lime to 2
soorkee. The latter is a puzzolana, and
should be made from thoroughly burnt
bricks. Sand is not often used as it can-
not be obtained coarse enough, and is,
besides, full of mica. It is sometimes
mixed with a proportion of soorkee to
prevent cracking in plaster, &c.
Kwikur is another lime-producing sub-
stance. Kunkur is, it is believed, found
only in India, and is generally supposed
to be produced by the filtering action of
water through coarse soil. The water,
of course, contains particles of lime.
These are deposited sometimes on the
surface and sometimes below the surface
of the ground. It is always found in
larger quantities near the hills, and at
the sides of old water channels than any-
where else, and at Pathankote. About
5 miles from that town there are several
places where kunkur is found on the
surface, with evident marks of its having
been formed around vegetable substances
— for instance, a kind of stalagmite,
formed around a stalk of grass or reed
— and one specimen was shown to the
author which distinctly showed that it
had been at one time the outer case of a
gnarled base of a tree, the impression of
the bark being distinctly traceable. The
usual kind found is about the size of po-
244
VAN NOSTRAND'S ENGINEERING MAGAZINE.
tatoes, in lumps, in which earth is more
or less mixed, but it is also found having
the appearance of stone, in layers from
2 to 4 feet thick, and about 3 to 5 feet
from the surface of the ground. About
Aligurh it is used as a building material,
and it has one peculiarity that it hardens
rapidly on exposure to the air. From an
analysis of kunkurs, near Goordaspur, it
appears that the average percentage of
carbonate of lime in the specimens was
50 or 51 per cent., and those about Seal-
kote, 52 to 53. This shows that kunkur
is a natural cement, and, though it is not
a quick-setting one, it is, nevertheless, a
fact that it is considered and treated as
a lime by most engineers. Some of the
kunkurs require an addition of fat lime,
and some of soorkee; but unless the lime
is burnt under strict supervision it is very
frequently adulterated, and it is now al-
most universally burnt with charcoal in-
stead of with cow-dung, as it used to be.
The usual way has been to load it into
clamps with oopla for fuel, but when
charcoal was used Y-shaped (in section)
kilns were introduced, in which the kun-
kur was either mixed with the charcoal
in proper proportions or else in alternate
layers of kunkur and charcoal, the light-
ing being done by igniting pieces of
charcoal and then pushing them into
vents left at the bottom of the kiln,
previously fitted with either charcoal or
oopla. The out-turn was fairly good,
but kilns of large size could not be em-
ployed owing to the precarious nature of
the out-turn; sometimes a high wind or
fall of rain would either burn a kiln to
clinker or make it under-burnt. A plan
has been recently adopted which was en-
tirely successful — viz., the clamp system,
but with charcoal fuel. Very good re-
sults were obtained, and the kiln could
be fired when required, or if fired could
be protected with mud plaster, until it
was necessary to open it. When burnt
the nodules are pounded fine, and should
be used with a very small amount of
water, and mixed with that only just
previous to use. The common practice,
however, is to mix it with a good deal of
water, and to leave it, sometimes for a
day or two. In the writer's opinion, this
simply ruins it, as he considers it a
cement, and not a lime. Pure cement
simply laid in a mould and not rammed
will, in most cases, harden under water
if left to harden in the air for 48 to 72
hours previously. In concrete it makes
excellent work, and it has a very nice
appearance owing to its reddish grey
color.
Floors. — There are, in Indian houses,
no second floors — at least, in the upper
provinces — and very few barracks have
them, so that the floors are, of course,
placed directly over the earthen filling in
of plinth. They are, as a rule, in Gov-
ernment buildings, of bricks or square
tiles 3 inches thick, laid over either a
concrete bed 4-§ inches thick or over a
course of bricks and bats. In private
houses they are seldom anything but
coarse mortar, hardly to be called con-
crete. In double-storied barracks the
upper floors are li| inch planks nailed to
joists carried on beams or trusses.
Hoof Coverings. — The roofs may be
said to be divided into two divisions —
flat and sloping. Flat roofs are by far
the most common, and trussed roofs are
only adopted in large public buildings
and barracks for European troops. Flat-
roof coverings are usually of the follow-
ing materials in the North-west prov-
inces : — 1st, a course of 12 inches X 12
inches, or 12 inches X 6 inch flat tiles, \\
inches to 2 inches thick, and over this
4 inches of well-beaten " terrace," which
is concrete or coarse mortar floated on
the upper surface with pure white lime
mixed with "goor," or coarse sugar.
This is very liable to crack owing to the
tremendous power of the sun in the hot
weather, and the cooling action of a
sudden storm of rain. These hair cracks
are a constant source of annoyance and
leakage, and require to be constantly
filled up with rosin and lime or Portland
cement. In the Punjab the flat-roof
coverings are of 12 inches X 6 inches X
\\ inch to 2 inch flat tiles covered with
\ inch to \\ inches plaster, well beaten,
and 4 inches of earth well beaten, covered
with 2 inches of mud plaster, or a com-
position of mud, chopped straw called
bhoola, and cow-dung. These roofs are
very cool, but require to have the weeds
pulled up before the annual rains, and
then replastered. If this is properly
done the roofs never leak. A cheaper
kind is made by laying thin boards over
the joists and then loose bricks and mud
as above. Stables and out-houses, also
the ordinary bazaar-house roofs, are of
FOOD VS. FUEL.
245
reed mats called "sirki," covered with a
coarser reed called " sirkunda," with the
mud above that. When beaten, plaster-
ed, and kept in proper repair, they do
not leak much, but the white ants are,
of course, very troublesome, and the
reeds have to be renewed every 7 or 8
years.
Tiled roofs are made of flat and half
round tiles, and over the joists there are
12 inches X 6 inches flat tiles, covered
with 1 inch plaster. Over this the tiles
called " Goodwyn " tiles are laid. These
are those just spoken of, and 200 are re-
quired to cover an area of 100 square
feet. The flat tiles are about 14 inches
X 12 inches and 1 inch thick, having the
sides turned up 1 inch. They are placed
side by side in a little fresh mortar, and
the half round tiles are then laid in
mortar over the abutting joints.
The "Jubbulpur" or "Allahabad"
tiles are similar in idea. The former are
| merely smaller tiles, one set being laid
| over the other, forming a double roof,
j very cool it is said, and the latter are the
| same with the exception of the lower
| half round, which are demi-hexagons, to
| enable 2 inches course of flats to be laid
evenly and to avoid slipping. Italian
tiles are very little used, as also slates :
— 1st, on account of their cost; 2d, on
I account of the heat, they being no pro-
jection whatever; and, 3d, on account of
I their being no protection from tropical
I rain. Slates and shingles are used in the
! bricks in double layers, where they serve
their purpose very well.
Thatching is not now much resorted
to, owing to the mutineers in 1857 having
i set them alight as a first measure to-
wards creating a disturbance. They
i make the coolest of any roof coverings.
! Slabs of stone are used in the central
: provinces at Saugor, but hardly anywhere
i else.
FOOD vs. FUEL-
CALCULATION OF THE NECESSARY FOOD
FOR A HORSE AT WORK.
By M. BIXIO, President of the Compagnie General des Voitures, Paris.
Translated from "Revue Industriellc" for Van Nostrand's Magazine.
It is evident that the quantity of food
required by a horse depends upon two
conditions : his weight, and the work he
performs. Upon his weight first, be-
cause in order to keep him in good con-
dition, it will be necessary to supply the
losses arising from respiration, perspira-
tion, and his internal functions; upon
the work that he performs, because all
work produces heat and this occasions
loss of weight.
In considering the conditions of the
life of the animal, we may count three
different states: 1st. That in which he
does nothing: 2d. That in which he
moves about but performs no work: and
3d. That in which he does some kind of
work.
The food necessary for his mainten-
ance under these conditions separately
we will designate in order: The Eation
of sustenance: The Ration of Transport-
ation : The Ration of Work.
The Ration of Sustenance is the food
necessary to keep him in good condition,
supposing that he remains in the stable.
The Ration of Transportation is the
amount of food in excess of the preced-
ing ration necessary to keep up his con-
dition if he moves about without haul-
ing or carrying any load.
The Ration of Work is the amount of
food in excess of the two preceding
amounts, required to enable the animal
to perform some useful work.
We will proceed to show how we can
arrive at a determination of the amounts
of these several rations, and then will
establish a general formula.
A food unit is a necessary basis of such
calculations, and the science of physiol-
ogy must supply our want. It is neces-
sary to determine among the mixture of
nutritive elements of the food what ones,
by their combination with oxygen in the
blood, disengage the heat which is the
source of the vital force necessary for
the muscular contractions.
246
VAN nostrand's engineering magazine.
p=^=-
From investigations upon this subject
made in Germany, England, and France,
the conclusion has been reached that the
nitrogenous or protein compounds are
chiefly instrumental in producing the
effect in question. The kilogram of pro-
tein has, therefore, been taken as the
alimentary unit.
M. Sanson, Professor of Zootechnic, at
Grignon, adopting this unit has arrived
at the following equation:
T
C
In which P is the protein necessary in
a ration, T is the work performed, and C
is the kilogrammeters of work produced
by a kilogram of protein.
The well known formula of mechani-
cal work is
T=F.E
in which F represents the force exerted
and E the path described. We know
also that the force exerted in hauling a
load is equal to the load moved, multi-
plied by the coefficient of traction.
If now we designate by M. the weight
of the horse, and by A the quantity of
protein necessary to sustain 100 kilo-
grams of his weight when at rest; then
if p be the ratio of sustenance we shall
have
JP=:MX0.01A
To determine the work produced by
the horse in transporting his own weight
to any given distance, we employ the
formula T=FE. In this case F is the
weight of the animal M, increased by m
the weight of his harness, and multiplied
by .OlB. B being the coefficient of
transportation, or the effort necessary to
keep in motion 100 kilograms of weight.
We have then
If now we represent by p" the protein
consumed in performing useful work;
by N the weight of the carriage; D the
coefficient of traction or the effort neces-
sary to draw 100 kilograms of weight
along the proposed road; the formula
for work becomes
T=N.01 DE
and Sanson's formula becomes
„ N .01 DE
P=— o —
Uniting in a single formula the three
different formulas above we have
F=p+p'+p"
whence by substituting the values de-
termined we get
(M-fm).lBE N .01 DE
P=M.01 A + -
.1 BE N
- + —
C ' C
in which the three different rations are
represented in succession.
This reduces to the form
p=.oi(MA+Er(M+"f+yp])
Such is the general formula for determ-
ining the quantity of protein for a horse
when at work.
If the animal works only on alternate
days, then he requires his sustenance
ration and so much of the ration of
transportation as will supply his neces-
sary movements about the stable or pas-
ture. If the sum of such movements be
represented by E' then the ration for a
day of rest would be
. M .01 BE'
P=.01 A.+
C
or
p=.oi (ma+™)
F=(M + W2).01B
or
T=(M-fm).0lBE.
If we represent by p' the protein of
the ration of transportation we shall
have in the formula of M. Sanson
P=T
C
(M-fm).OlBE
C
in which m is the weight of the harness
or of saddle and rider if the horse carry
such.
P
The general formula then
tein required for two days,
and one of rest, is
P=.0l/2MA +
E[(M-H?2
for the pro-
one of work
)B + ND] + MBE^
C
which may be written
P=.01^2MA +
M(E + E')B + E(mB + NDy
C
FOOD VS. FUEL.
247
In this formula
P=the protein necessary for two days.
M=the weight of the horse.
m=the weight of his harness.
N=the weight of the carriage.
A=the coefficient of sustenance.
B = the coefficient of transportation.
D = the coefficient of traction.
C=the mechanical equivalent of a kilo-
gram of protein.
In order that this formula shall be of
use the values of the coefficients A, B, C
and D must be determined. This is an
object of importance in our industry.
It is necessary to remark here that the
above formula is based on the idea that
nitrogenous materials in the food are
necessary for the production of force.
This theory is disputed by M. Voit,
who claims that the consumption of
nitrogen is no greater in working than
resting, while the combustion of carbon
and of hydrogen is greatly augmented.
Prof. Herve Mangon proposes to
establish a formula based on the follow-
ing facts :
"An animal is a machine for combus-
tion. His food is the fuel and his void-
ings are the ashes. Analysis of the fuel,
and the ashes determines what and how
much has been burned."
" The burnt portion contains a determ-
inate amount of carbon and hydrogen,
which in burning have produced a defi-
nite number of heat units."
" The number of heat units multiplied
by the mechanical equivalent of heat
will give the theoretical number of units
of work in kilogrammeters."
" This, multiplied by the proper coeffi-
cient, gives the result in units of work
obtained.
In working upon this basis Prof. Mag-
non remarks that the difference between
the winter and summer rations may be
taken in account.
This idea of establishing a formula is
based on the mechanical theory of heat,
and the above propositions indicate that
observations and experiments upon the
animals themselves are of the first
importance.
This is not merely a solution of a
purely scientific problem but one of
great practical utility to an important
industry. It is to determine how we
shall best nourish our horses so that they
perform their work at the least expense.
The nitrogenous elements of food are
the most costly ones and we shall econo-
mise if we can obtain the requisite force
from the carbon and hydrogen only.
But it may be urged on physiological
grounds that nitrogen plays an important
part in sustaining the animal, and our
general formula, taking account of sus-
tenance, calls for a certain amount of
protein; only it may be modified per-
haps by determining how much carbon
and hydrogen are necessary to produce
the useful effect T.
The values of the coefficients in our
formula remain yet to be determined.
It is generally admitted that for the
purposes of sustenance 30 grams of pro-
tein are required for each 100 kilograms
of weight of body. Therefore A in the
formula represents 0.03&.
In some experiments upon carrying
loads M. Sanson concludes that for the
horse a constant effort of 10 kilograms
is necessary for each 100 kilograms of
weight carried at a trot. B in the
formula would therefore equal 10.
Morin's experiments upon traction on
roads give — for a coefficient upon a dry
pavement, 6 per 100 drawn at a trot
and 3 per 100 at a walk. Upon the
hypothesis of working at a trot the co-
efficient D would be 6. From experi-
ments by M. Plessis, an engineer in our
employ, made upon our own vehicles
and upon the several routes, it would
seem that this coefficient 6 is too high
by nearly one half.
Finally the coefficient C the most
important of all has been a matter of
research by M. Sanson, who concludes
that one kilogram of protein ought to
produce 1600000 kilogrammeters of
work.
Consequently C = 1600000
We believe for our part that this co-
efficient which has been calculated from
the work of omnibus horses is too high.
We find in Prof. Mangon's work:
(Traite du Genie Rural) a calculation
which assigns to 258 grams of oats a
useful effect of 100000 kilogrammeters.
It was obtained by observation of agri-
cultural horses working at a walk.
To produce 1600000 kilogrammeters
of work would require 4k.128 of oats
containing 462 grams of protein; less
248
YAK NOSTKAND's ENGINBEE1NG MAGAZINE.
than half the amount determined by M.
Sanson; but it must be remembered that
this latter figure is based on working at
a walk.
On the other hand we find in the same
work, that for the Cheveux de poste of
Paris that 1 kilogram of oats is required
for 100000 kilogrammeters of work.
This is equal to lk.798 of protein for
1600000 kilogrammeters, which is much
more than M. Sanson's estimate. We
see from these different estimates how
important it is that we should determine
by careful experiment the conditions of
our particular service.
Suppose we have to determine the
ration of a horse drawing our coupe No.
4 for one day and resting the next. The
mean weight of the vehicle and load
(carrying from one to three passengers)
is 533 kilograms. The mean weight of
the horse is 420ft; the harness weighs
14&. The route is about 50 kilometers.
The horse during his day of rest does
not move more than 300 meters.
The equation for rations, making the
substitutions, becomes
P.01 = (2420X.03 +
50300 X420X10+(14X 10+533X6) 50000
1600000 /
which reduces to
P=2k 364.
This is the quantity of protein necessary
to give a horse in two days when he
works one of them under the above con-
ditions.
If oats alone, (containing 7.93 per cent,
of protein) are given to the horse the
gross weight of the ration would be
2Sk423. But other food such as hay,
corn, bran, etc. etc., is necessary.
We will suppose there is given to the
horse during the two days
5 kilos, hay containing .5055 of protein.
5 kilos, straw containing.! SI 8 of protein.
0.4 kilos, bran containing .0553 of protein.
Total 0k7426 "
This would render necessary for the pro-
tein of the oats only
2k.364-0k7426 — lk.6214
which corresponds to a weight of
20k446
In our tables of rations actually given
to our horses (Nov. 1877) we estimate
the protein at lk6892 which would
correspond to a weight of oats=21k.301.
We feel assured that our equation has
a practical value but that for general
use, it will be necessary to establish the
values of the different coefficients separ-
ately for the different kinds of work
which horses are required to perform.
Some further experiments are neces-
sary to obtain precise values of the co-
efficients for the varying conditions of
our own service.
But in the above analysis, we have
determined the question— upon what
basis a good ration should be established,
and what elements are to be considered
in the calculation.
In treating fully the second part of
this question, it will be necessary to
determine not only the protein but the
proportionate quantities of the other
constituents of the food. This would
require two more equations to determine
exactly the conditions of a good ration.
BUILDINGS AND EARTHQUAKES.
From "The Building News.'
Although in this country earthquakes
are happily rare, we know that in south-
ern and eastern lands they are of such
frequent occurrence that the architect
has to take the stability of his structures
into serious consideration. Indian and
Eastern architecture generally has been
considerably modified by conditions due
to this cause, and we know that the Ital-
ian medievalist introduced so largely the
tie into his arched openings as to sacri-
fice, in great measure, the motive and
beauty of the pointed' style. Japan has
especially suffered from visitations^ of
earthquakes, and it is not surprising that
the engineers and others engaged in con-
BUILDINGS AND EARTHQUAKES.
249
struction should pay special attention to
the means best adapted to overcome the
shocks to which buildings are exposed.
We have before us two pamphlets by
Mr. John Perry and Mr. W. E. Ayrton,
Professors of Engineering in the Imperial
College of Tokio, Japan. In one of these*
the authors investigate the effects pro-
duced by an earthquake on a structure,
especially with regard to the time of vi-
bration. Generally it has been assumed
that the shock caused by an earthquake
produces an impact upon a building, but
recent inquiries have shown that it is a
wave of elastic compression in any direc-
tion, vertically or horizontally, through
the earth's crust. These waves of undu-
lation, if we may so call them, are no
doubt transmitted to the surface in a
modified manner owing to surface irregu-
larities, such as mountain ranges and
geological structure. Rocky strata, of
course, transmit them rapidly. But we
have to regard an earthquake as an elas-
tic compression in some direction. This
being so, it follows that a building is af-
fected by an undulation, or rather par-
ticipates in the vibration of a point of
the earth's surface, which vibration may
be mathematically determined, or at least
approximately so. If we imagine such a
wave of vibration to pass under a large
building, such as the Law Courts for ex-
ample, it is obvious some portions of the
structure would be affected in a greater
degree than others. The lofty square
towers would vibrate slowly, compared
with the lower parts, and according to
the relative height and homogeneity of
the masses would be the amount of
vibration each part would share. For
instance, in a low building we may fairly
assume the time of vibration of the shock
and of the structure to be approximately
equal, if the parts are of the same
density ; but if the building is lofty it
will vibrate more slowly. A slowly vi-
brating structure is necessarily subjected
to stresses of a complicated kind, and
more severe than those of a quickly
vibrating one. It is not difficult to com-
prehend the truth of this proposition,
and Messrs. John Perry and W. E. Ayr-
ton have shown that the stability of
structures subjected to earthquakes de-
* On Structures in an Earthquake Country. By John
Perry and W. E. Ayrton, Professors in the Imperial Col-
lege of Engineering, Tokio, Japan.
pends mainly upon the quickness of their
vibration, or, in other words, on their
rigidity of structure and lowness. A
slowly vibrating structure — that is to
say, a lofty building — will probably, as
our authors say, " get broken in its con-
nections with the foundations, if these be
rigidly fixed to the ground ; conse-
quently (and we must here oppose the
practice of many architects and engin-
eers) putting a heavy top to a lighthouse,
the chimney of a factory or other high
building, must certainly take from its
stability." As they observe, "it is the
relative velocity of the base of the struc-
ture, with regard to the other parts, which
is the fixed quantity, and therefore that
the more massive the structure, the more
momentum enters it through the base."
An ordinary Japanese two-storied house,
with its heavy roof, it is supposed, takes
four seconds to make a complete vibra-
tion, the restoring forces which bring the
structure back to its normal position be-
ing due to stiffness of the joints, and to
the fact that the house is not rigidly
connected with the ground. It wTill sur-
prise the English architect to learn that ■
the Japanese houses are without the
foundations we are accustomed to use ;
the vertical posts rest on detached stones,
and there are no diagonal braces. Thus
the building can be displaced from its
position of equilibrium by any shock
without fracture occurring. There is a
" viscous resistance," as the authors term
it, to the motion, caused by the various
joints, and such resistance diminishes the
motion and adds to the safety of the
building. Particular stress is laid on this
viscous resistance of the joints, and also
to the absence of diagonal pieces to lessen
the strains. The Japanese temples are
considered pretty secure against shock,
as they are buildings of slow vibration,
and have a great deal of viscosity in their
joints. It must be borne in mind that a
rigidly connected foundation is independ-
ent of the mass of building, and the
shock tends to displace at any weak point
or surface of contact between different
portions. All non-homogeneous build-
ings have some parts only capable of
slow vibration compared to others. The
authors justly say that there is a best
method of constructing buildings in an
earthquake country: this obviously con-
sists in constructing the lower parts of the
250
van nostrand's engineering magazine.
building with yielding material, so that
the shock from, an earthquake may be re-
duced in intensity and the vibration of the
upper part diminished. A rocky or rigid
foundation, on the other hand, transmits
the vibration or momentum undiminished
to the upper parts. Again, a foundation of
yielding timber or some soft elastic sub-
stance would form a cushion by means of
which the time of transmission of the
momentum due to the shock may be in-
creased. The authors point out it is
desirable to keep houses built of ordinary
wall thicknesses, with brick and common
mortar, as low as possible — at most not
more than two stories high ; but if good
cement be employed instead of bad mor-
tar then their height may be safely two
or three stories. Another point is the
horizontal vibration of the ground. This
causes a kind of shearing stress in the
joints which mortar cannot transmit, and
it is desirable, therefore, to make the
joints rigid in cement so that the walls
may resist a sliding as well as a crushing
stress. No doubt we have here a strong
argument in favor of cement concretes
for building walls in earthquake coun-
tries. At any rate it is laid down that
the#most suitable structures for these
contingencies, if of stone, are those built
of large stones set in good cement with
walls of considerable thickness at the
base, diminished gradually in proportion
to the mass and height of the building,
and we have a strong presumptive argu-
ment in favor of pyramidal buildings.
As timber has greater tensile resistance
to shock, and as the mass of timber in a
building is small, a building of this mate-
rial is even more desirable if constructed
with strong joints, while wrought iron
and steel have still stronger claims in
these respects. Another hint is given —
namely, that timber structures should
not be too rigidly fastened to the earth.
Without going into the calculations of
the times of vibration of different build-
ings given by the authors, as regards
shape and height, it is obvious the con-
clusions drawn by them are convincing ;
and that, to insure stability in structures
liable to shocks, the relative vibrations of
the parts of the structure of any given
material must be taken into account.
Thus, high chimneys, such as many
engineers have erected recently, crowned
with heavy cornices, are unsafe in a
country like Japan : for, as the authors
show, the period of natural vibration of
a chimney 150 ft. high and 10 ft. square
is about 2j seconds — a period much too
slow to be safe when connected with the
walls of a building of less height and
consequently of less vibration.
We here turn to another very interest-
ing paper read by the authors before the
Asiatic Society of Japan,* in which the
motion caused by an earthquake is in-
vestigated. The principle our authors
set out with is that it is possible to read
an earthquake message by the motion of
a body attached to the earth by springs.
Thus " the centre mass of a body fastened
by means of springs inside a metal box
rigidly attached to the earth has in cer-
tain cases motions with respect to the
box itself which in miniature with great
exactitude represent the motions of a
point of the box during the earthquake."
Here we have a self-evident principle
upon which an apparatus for recording
vibration can be constructed. Without
diagrams it is difficult to convey a cor-
rect idea of the seismometer of Messrs.
Perry and Ayrton. But we may describe
it briefly as a strong iron case rigidly
fixed to the rocky crust of the earth,
with a leaden ball of 400 lbs., supported
by five strong spiral springs, four of
which are horizontal and one vertical, all
having the same period, so that if there
were no friction the ball would describe
an ellipse when freely vibrating. To re-
cord the different horizontal movements
there are three arms with pencils ; these
are made to press by means of spiral
springs on a band of paper moved hori-
zontally by clockwork. By these and
other means an automatic register of the
motion of the earth is diagrammatically
made, and these diagrams assume irreg-
ular spirals on the paper. Thus the posi-
tion, velocity, direction, and acceleration
of the ball at any moment is recorded,
and therefore the motion of any point
upon the earth's surface is also registered.
Professor Palmieri and others have in-
vented electro- magnetic seismographs, to
record earthquake vibrations and. in-
tensities, but the exactitude of the records
made has been questioned by Mr. Mallet
and other authorities in the science of
* On a Neglected Principle that may be Employed in
Earthquake Measurements.
THE ACTION OF BRAKES.
251
seismometry. We may simply add that
the authors propose to place three of
their instruments on the plain of Yedo,
with clocks in telegraphic communica-
tion, by which means the vibration and
motion of an earthquake-wave could be
determined. We only hope the ingenious
authors will be assisted in their experi-
ments by the Japanese Government, and
that facilities to perfect their instruments
will be afforded them in the interests of
science and humanity.
THE ACTION OF BRAKES.
From "English Mechanic."
The remarkable and unexpected results
obtained during the elaborate experi-
ments with railway brakes, made a few
weeks ago on the London and Brighton
line, formed the subject of the paper
read by Captain Douglas Galton, at the
meeting of the Institution of Mechani-
cal Engineers held in Paris. These ex-
periments form the first of a series
which it is intended to make with the
view of ascertaining (1) the actual pres-
sure required to produce a maximum re-
tardation of the revolving wheels at dif-
ferent velocities; (2), the actual pressure
exerted by the different forms of contin-
uous breaks now in use; (3) the time
required to bring the break- blocks into
operation in the several parts of the
train; and (4), the retarding power of
the existing continuous brakes, tested
on trains running under similar condi-
tions of weight and speed. From the
enumeration of these heads it will be
readily understood that when completed,
we shall have the most important con-
tribution to the literature of the brake
question which has hitherto been made;
and the first instalment, contained in
Captain Galton's paper, is sufficient evi-
dence of the probable value of the series.
The experiments described were under-
taken to ascertain the co-efficient of
friction between brake-blocks and
wheels and between the wheels and rails,
both when the wheels are revolving and
when skidded. It is scarcely necessary
to insist on the importance of ascertain-
ing by actual test the exact value of a
co-efficient upon which the whole sys-
tem of brakes depend; and the engineer-
ing world is much indebted to the
London and Brighton Railway Company
for the manner in which they have taken
up the question and facilitated the car-
rying out of the experiments. The ex-
perimental van and the recording appa-
ratus were designed and constructed by
Mr. Westinghouse and Mr. Stroudly re-
spectively; but for our present purpose it
is unnecessary to give a description of the
means taken to obtain the results. The
latter are unquestionably as correct as
ingenuity and care could make them,
and if they are remarkable, they serve
to show that it is the unexpected that
always happens. The experiments un-
der notice were made at the end of May
near Brighton, the first day being dry
the second stormy, and the third fine,
with showers. There was thus a suffi-
cient variety of weather to render the ex-
periments of more value than they
might have been if made under uniform
conditions, but there was not time to
collate all the results before sending in
the paper. Captain Galton, therefore, ex-
hibited only a few of the diagrams taken,
but these were of so remarkable a char-
acter as to excite the keenest attention
of the engineers present. In experi-
ment No. 15, May 28th, the brake-van
was slipped when traveling at the rate
of 40 miles an hour. The pressure on
the brake-blocks remained nearly con-
stant during the experiment, and being
greater than that required by the co-
efficient of friction between the brake-
blocks and wheels due to velocity, the
friction increased so rapidly as to cause
the wheels to skid immediately. The
friction at once decreased rapidly, but
rose again as the speed diminished, at-
taining the maximum as the train came
to rest,, which it did after many jerks in
12^ seconds. In experiment No. 16,
May 28th, the van was again slipped —
the speed being 46 miles. The pressure
of the air was less than in the previous
252
VAN NOSTRAND7S ENGINEERING MAGAZINE.
experiment, and it was gradually dimin-
ished during the experiment; conse-
quently the pressure on the blocks was
correspondingly reduced. At first the
friction between blocks and wheels de-
creased slightly, but, when the velocity
diminished the friction increased rapidly
and the van came to rest without a jerk
in 12 seconds. Thus the quicker stop
was made by the revolving wheels which
originally were traveling at a higher
speed than in the case of the skidded
wheels. This effect was exhibited in a
decided form by experiment No. 3, May
28th, in which the speed was 44J miles.
The pressure applied to the blocks was
sufficient to skid the wheels at once, and
the diagram shows that the co-efficient
of friction between the blocks and the
wheels decreased immediately after the
skidding and did not rise until the end
of the experiment, while tractive force
on the draw bar, at first increased by the
act of skidding, largely decreased as
soon as the wheels were held by the
blocks. In experiment No. 3, May 29th,
the engine and van were brought to rest
from a speed of 39 miles an hour. The
air was allowed to escape from the cyl-
inder through a small hole after the
the brakes were applied, so that the pres-
sure decreased during the whole experi-
ment. The diagram in this case shows
that the retarding force due to the pres-
sure of the blocks was at first diminished
until the reduction of velocity reached
the point where the increase in the co-
efficient of friction was sufficient to over-
come the effect of the diminished pres-
sure applied to the blocks. At this
point the retarding effect was increased,
and the wheels were skidded. The
curve immediately rose in a nearly ver-
tical line showing that the co-efficient of
friction became very great as the wheels
came to rest — the time during which the
wheel was partly rotating, partly slip-
ping being almost inappreciable. Im-
mediately after the rise, the curve fell to
a point far below its original position.
Thus showing that with skidded wheels
there is a great diminution in the retard-
ing effect of the brakes. As the velocity
continued to decrease the curve steadily
rose, thus showing that the co-efficient
of friction between the rails and skidded
wheels increases as the velocity dimin-
ishes. At the moment of coming to rest
the co-efficient of friction became very
great. The results obtained in these ex-
periments may be taken as a fair sample
of the series; from which we learn that
the application of brakes to wheels does
not appear to retard the rapidity of their
rotation, but when it falls below that
due to the speed at which the train is
moving, immediate skidding is almost
inevitable. The resistance resulting
from the application of brakes without
skidding is greater than that caused by
skidded wheels. During the moment of
skidding, the retarding force increases
enormously, but immediately afterwards
falls to less than that what it was before
skidding. The pressure required to skid
is much higher than necessary to hold
the wheels, and appears to have a rela-
tion to the weight on the wheels them-
selves as well as to their adhesion and
velocity. On this point Captain Galton
says: — "It would seem that the great
increase in the frictional resistance of
the blocks on the wheels, just before and
at the moment of skidding, due to the
increase in the co efficient of friction
when the relative motion of the blocks
and the wheels become small, is what
destroys the rotating momentum of the
wheel so quickly". With constant pres-
sures the friction between the blocks
and the wheels increases as the velocity
decreases, until, as the experiments
proved, the wheels are skidded. But it
was also discovered that in order to ob-
tain the maximum retarding effect the
wheels ought never to be skidded, but
the pressure on the wheels should at all
times be just less than is required for
skidding. In order to effect the desired
result, then, the pressure between the
blocks and wheels ought to be very
great when first applied, gradually dim-
inishing as the train comes to rest. Such
an outcome from these experiments dis-
closes the fact that all the hand-brakes,
and most of the continuous brakes, have
been designed to suit conditions which
do not exist in practice. The old saying
— you can do no more than skid — is
shown to be utterly erroneous, and the
most successful brake is that one, the
inventor of which has unconsciously
as it seems, grasped the true principle.
That the skidding of wheels is not the
best way to stop a train has been known
and urged persistently by some railway
THE ACTION OF BEAKES.
253
men, and the drivers and guards on
most lines have orders to release the
brakes when the wheels skid; but, until
these experiments demonstrated the fact,
not a few drivers and others, engineers
amongst them, firmly believed that the
skidding of the wheels was the readiest
method of stopping. It has been object-
ed to mostly because of the wear of the
tires — flat places being highly objection-
able. So long ago as 1346 Mr. Gooch,
while connected with the South Western
Railway, issued a rule to his men that
wheels were not to be skidded, and if
skidding did take place the brakes were
to be immediately released and applied
again. Mr. Tomlinson said that every
practical engine-man knew that the
skidding of wheels was a great mistake;
but we venture to think that Mr. Tom-
linson need not travel far to find plenty
of practical engine-men who would argue
the point with him. The gentleman
who preceded him in the discussion, Mr.
Haswell, expressed his surprise at the re-
salts of the experiments described by
Capt. Galton, as the Newark trials had
led the commissioners to form a contrary
opinion as to the value of skidding. Mr.
Brown, of Winterthur, speaking from
practical experience on lines of heavy
gradients in Switzerland, declared that
if the wheels were skidded much of the
retarding force was lost. Mr. Yeomans
said that when the vacuum brake was
first applied on the Metropolitan a
vacuum of 15 inches (?) was found to
skid the wheels. The drivers were,
therefore, ordered not to exceed twelve
inches. He controverted the opinion
that the greatest pressure ought to be
applied first, and thought that a sudden
application of brake-power destroyed
the wheels. Unfortunately no reasons
were offered for these opinions, save that
Mr. Yeomans had seen wheels that had
been destroyed by the sudden applica-
tion of the Westinghouse brakes. He
considered that Capt. Galton's experi-
ments had only confirmed what was well
known, and that, to obtain any useful
information, experiments extending over
many years of actual service were neces-
sary. The companies, however, it must
be remembered, have had the hand-brake
in use for many years, and it has been
left to persons not specially connected
with railway work to point out that the
hand-brake is radically wrong — for, as
every one knows, it is impossible to al-
ways avoid skidding with it. In view of
that fact, and of the statement that the
evil effects of skidding were well known
a quarter of a century ago, it does not
say much for the inventive skill of the
profession that hand-brakes were not
long ago improved off our trains. The
explanation of the diminished retarding
force when the wheels are skidded is
most likely that given by Prof. Kennedy,
though it might be worth while to study
the question experimentally by means of
heavy weights resting with a small sur-
face on a metal rail. As long as wheels
revolve, says Prof. Kennedy, the surface
in contact with the brake is continually
changing, so the tire does not become
highly polished, but directly the wheels
are skidded there is theoretically only a
point, and practically only a very small
surface, taking all the friction between
the rail and the wheel. This surface
must be almost instantaneously polished,
and the wheel consequently slips along
with the least friction possible between
it and the rail; for, as is shown by the
experiment, the friction increases as the
velocity decreases. The paper has now,
however, drawn attention to the subject,
and it is to be hoped it will be worked
out in a thoroughly scientific manner.
Capt. Galton deserves thanks for what
he has already done, and it is not too
much to expect that the companies gen-
erally should afford facilities for carrying
out further experiments.
The discovery of an extremely simple
and cheap means to protect houses from
being struck by lightning has recently
been announced in a French agricultural
paper. This consists in the use of
bundles of straw attached to sticks or
broom-handles and placed on the roofs
of houses in an upright position. The
first trials of this simple apparatus were
made at Tarbes — Hautes Pyrenees — by
some intelligent agriculturists, and the
results were so satisfactory that soon
afterwards eighteen communes of the
Tarbes district provided all their houses
with these bundles of straw, and there
have been no accidents from lightning
since in the district — at least, so says
Nature.
254
VAN NOSTRAND'S ENGINEERING MAGAZINE.
IRON AS A BUILDING MATERIAL.
From "The Architect.
Using a popular formula of speech,
it is often said that iron is the material
of the future. The fancy of the philoso-^
phic builder is supposed to run over a
hundred instances in which the mere
commonplace substances used in con-
struction are found wanting. Visions
of what might have been if ingenuity
had not been hampered in its enterprise
by the conditions attaching to mere
stone and brick, timber and boards, are
supposed to overwhelm his mind. He
finds rest in the contemplation of the
Crystal Palace, the St. Pancras roof, the
Britannia Bridge, the Vienna dome,
perhaps the Great Eastern, the Devasta-
tion, and the Thunderer. " Ah, well ! "
he reflects, "iron is the material of the
future; the time will come, although I
shall not live to see it, when a gentle-
man will run his iron house down to his
place in the country by rail in August,
and up again to the Belgravia of the
day in February; when balloons of No.
40 or 50 gauge sheet will travel daily
between London and New York; and
wThen a new St. Albert's Cathedral, in a
central situation at Wimbledon, will be
built of Professor Barff's best black
oxidised." Professor Barry, for in-
stance, of the Royal Academy, who offi-
cially might not have been expected to
look so far ahead, is amongst others as
enthusiastic upon this point as could be
desired. The architecture of the world
in the future can scarcely fail, he says,
to be modified by our scientific knowl-
edge of iron, which as a building mate-
rial has been almost discovered by the
present generation. From the Egyptians
— to whom it is, of course, impossible
not to allude — we have no doubt much
to learn; from the Greeks also. But
had the Romans known as much about
iron as we do they would have been
able to teach us something. The medi-
aeval builders also would not have clung
to their primitive arcuation if they had
known about iron. In the present day
architects are too considerate of the
past; if they would but consent to let
engineers help them in construction in
exchange for similar assistance in deco-
ration— in short, iron would then be-
come the material of the future.
The Conference of Architects, which
was held last week, seems to have dealt
with iron, if nothing else, seriously.
Professor Barff explained his system of
creating upon the surface of this metal
— as the weather does upon certain
others, such as lead and zinc — a pre-
servative oxide. Under the presidency
of Mr. George Godwin a variety of
fireproof inventors discoursed to each
other upon the protection of iron from
its inevitable destruction in great fires.
Mr. Barlow, C.E., described at another
meeting the construction of an iron roof
recently designed by him; and thereupon
Mr. E. M. Barry wound up the whole
with the thoughtful reflections we have
quoted. If nothing comes of all this, it
cannot be said that architects have not
at least, and at last, taken the subject
into consideration.
But there are people of still more care-
ful habits of thought, who will shake
their heads, and say that nothing can
come of it after all. Indeed, when Mr.
Barlow, speaking incidentally of the
great '1 ubular Bridge of Robert Stephen-
son, tells us of one thing being perfectly
clear — that no such structure will ever
be built again; and when Mr. Carroll, of
" unpractical romantic Dublin," tells us
how he and an engineer companion, as
they traveled along it, shook in their
shoes with a great fear lest the wonder
of the world should shake itself and all
that was within it forthwith into eterni-
ty, by reason of the " tons upon tons "
of ruinous red rust shaken perpetually
from its dreadful flanks; these authori-
ties are indicating pretty clearly that
the scientific mind is already being
rapidly disillusioned, and that before
long there will be no one left to believe
in the perfectibility of iron buildings,
unless it be such a one as a professor,
whether of architecture or of chemistry,
in the Royal Academy.
It is by no means a paradox to say
that Nature does not undertake to sup-
ply man with building materials. He is
I permitted, no doubt, to hew stone from
IRON AS A BUILDING MATERIAL.
255
the rock, and to fell timber in the forest,
and it must be acknowledged that these
accidental products have gone very far
indeed to serve the builder's purposes;
but the not unreasonable theory that the
artificial objects of building must be
taken to point to the use of correspond-
ingly artificial materials is one that has
in reality been exemplified from the
most primitive ages — in the invention,
for instance, of such an odd thing as
brickwork; and when we are led in
modern times to try what can be done
with iron, it is the self -same principle
that is manifesting itself— building is
being driven by its own essential artifi-
ciality to seek artificial materials. In
other words, reasoning upon the matter
a priori, if not otherwise, we are entitled
to say that Nature cannot be expected
to provide to the architect and the engi-
neer, more than to the machinist, any-
thing beyond the crude components out
of which he shall make for himself such
materials as shall best serve his ends.
But however this may be, it is plain
enough that in this respect the line must
be drawn somewhere which shall divide
the practicable from the impracticable;
and it is, perhaps, more than probable
just now that that line must be taken to
exclude iron in a very great measure
from the list of true— that is, permanent
— building materials, and to leave it
almost entirely to mechanical engineer-
ing and other such manufacturing art as
its more proper province. Such per-
fectly artificial materials, for instance,
as brick, terra- cotta, artificial stone, con-
crete, cements and plasters, lead, glass,
paint, and so on, answer the builder's
artificial purpose admirably. There are,
likewise, many appliances of building,
akin to mechanical work, in which iron
is almost as invaluable as it is to the
mechanician generally. There are also
certain incidents of building in which,
for even structural features, iron comes
to take the place of timber with excellent
effect, as in columns and girders judi-
ciously introduced. But here it would
really seem as if we must stop for ever;
crude as natural stone may be, iron can
not take its place, and, fatal as may be
the effect upon timber of the dilapida-
tion of centuries, the case of iron as a
substitute is much more serious within
much shorter periods of time.
The employment of iron in ordinary
i building is to be fairly described as being
altogether that of an equivalent for tim-
, ber. The principles involved — those of
J the post and girder, the bent arch, the
| truss, and whatever else — are precisely
I those of timberwork, and a sheet-iron
; covering merely takes the place of board-
I ing. Bolts and rivets represent screws
| and nails, and even the angle iron has its
: prototype in the work of the joiner. The
i only advantages derived from the use of
j the metal are in respect of strength and
i lightness, complexity of scientific design,
; and minute precision of calculation.
I Apart from these considerations, wTe
. might just as well even now be depend-
| ent exclusively upon our old-fashioned
'fir and oak — old fashioned. no doubt, but
i still as far as ever from being obsolete.
: Where, then, is the great drawback in
, the use of ironwork ? Why is it that it
; it has not during the last fifty years,
; since the invaluable article of poor Cort's
(invention — rolled iron — has become so
intimately available and so cheap, ac-
i quired an absolute ascendancy over the
timberwork which seems by its side so
! clumsy and unmanageable ? The answer
! may be given in single word — Rust. Of
| all metals, perhaps this, the most useful
in a thousand ways, is the worst to wrear
j against the weather. Moisture in the
j simplest form is its deadliest enemy.
| Lead or zinc, for instance, as we have al-
ready hinted, when exposed to atmos-
pheric action, becomes coated with an
oxide of itself, which renders paint use-
less as a preservative ; but iron, in form-
ing its oxide in the same circumstances,
develops a process of absolute disintegra-
tion, and falls rapidly to powder, and no
preservative process yet known will pro-
tect it. Common painting, it has to be
borne in mind, is simply the act of at-
taching to the surface of any more
perishable material a coating of carbon-
ate of lead as a material less perishable
and easily renewed. Not merely oil
paint, however, but the application of a
coating of zinc, a much more scientific
and successful invention, is scarcely of
any permanent use in practice; and if
we fail in protecting our ironwork from
disastrous rust, we fail in making it really
serviceable as a recognised building
material. Not only the architect, but
the engineer none the less, must ac-
256
VAN NOSTRAND'S ENGINEERING MAGAZINE.
knowledge this; and when the architect
is obliged to discard iron in so great a
measure, it becomes a question of time
when the engineer also may have, how-
ever reluctantly, to regard it with
universal anxiety.
Supposing that the general surface of
the iron may, by the judicious applica-
tion of some specially judicious coating,
and its frequent renewal, be kept quite
free from oxidation, this unfortunately
does not help us after all. It is the pe-
culiarity of ironwork that it is never at
rest. It expands and contracts consider-
ably under ordinary changes of tempera-
ture. It vibrates still more considerably
under ordinary pressures. If, therefore,
we are obliged to put it together by
means of such a process as riveting — if,
in other words, we have to make it up of
small pieces pinned together — then are
these considerations which at once appear
with reference to rust. A thousand
joints offer access to the microscopic in-
fluence of atmospheric moisture in a
thousand places. A thousand pins — call
them by what name we please — are in
one way or another constantly moving
under strain, however minute their move-
ment. Nor is this all; for, in the very
act of putting the work together at first,
if any preservative had been previously
applied to the surfaces that are now
brought into contact under the force of
the smith's hammer, it is only too plain
that at the very weakest points of all the
preservative has been abraded quite
away, and the veriest nakedness of the
metal exposed again to the most direct
and rapid creation of rust. Not only oil
paint, but what is called the galvanized
coating of zinc, is obviously immediately
rubbed off whenever a rivet is ham-
mered, or even a bolt tightened by a
wrench. What makes the case still
worse is the circumstance that oxidation,
when once begun, will insidiously con-
tinue to progress even under the pre-
servative coating. It is easy, then, to
see that, of all materials as yet employed
in building, iron is in practice the most
incapable of defence against a peculiarly
disastrous decay produced by the most
commonplace, most universal, most un-
avoidable, and most insidious process of
attack. The invisible and motionless
vapor of the air, which nourishes the
world, is the inevitable and special
destroyer of the mightiest substance
manufactured by the ingenuity of
man.
That these reflections are a serious
check to the aspirations of building
science it is needless to deny, but enough
has been said to show even to the mean-
est capacity that, so far as it has yet
gone, iron is emphatically not the mate-
rial of the future.
THE BRITANNIA BRIDGE.
From "The Engineer."
At a recent meeting of one of the
architectural societies it was gravely
stated that the great bridge of Stephen-
son's was rusting away. The process of
decay was progressing with alarming
rapidity; consumption, in its worst form,
had seized upon the noble structure; the
disease was incurable, and its days were
numbered. These statements publicly
enunciated naturally somewhat alarmed
outsiders, who began to entertain the
notion that they might perhaps be cor-
rect, and that, at any moment, the
Straits of Menai might engulph the
Britannia Bridge and the Irish mail, pas-
sengers and all. We trust the protest of
the engineer-in-chief of the London and
North Western Railway, published in
our daily contemporaries, has dissipated
so absurd and unfounded an idea. It is
just possible that it may have occurred
to some one that since many old stone
bridges over the Thames have disappear-
ed, and Waterloo Bridge, upon excellent
authority is shortly to do the same, that
it was high time, upon the principle of
fair play, that an iron bridge ought to
begin, at any rate, to show some signs
of decay.
The Britannia tubular bridge belongs
to a particular class of structures of
which we shall never see any more ex-
THE BRITANNIA BRIDGE.
257
amples. As it is, that class has been re-
produced, we believe, in only two in-
stances; one of these is the Victoria
Bridge at Montreal, and the other, a
bridge of the same name in Australia.
There can be very little doubt that the
idea of the tubular form was either sug-
gested to Stephenson, or if conceived
upon other grounds, he was confirmed in
the idea by the information he received
from Fairbairn with respect to the
strength of iron ships. An iron ship,
allowing for the difference in form and
other details of design, represented then
as it does now a complete iron tube, if
we regard the deck as constituting the
upper boom. If, again we imagine the
ship supported, as no doubt she often is,
near each extremity upon the crests of
two waves, she becomes an absolute
tubular girder for the time being. It
must not, however, be supposed that be-
cause we shall not construct any wrought
iron bridges upon the model of the
Britannia Bridge, that we thereby con-
stitute any argument against its original
merit, its present security, or its future
durability. We are not likely to build
any cast iron bridges in accordance with
the design of Southwark Bridge; but
that does not prevent that structure from
possessing the largest span in cast iron
in the world. The nearest approach to
it, with the exception of the Sunderland
Bridge over the Wear, are the seven
arches of the bridge of Tarascon over
the Rhone, which have a span of 203
feet each. It is now nearly thirty years
since the Britannia tubes began doing
their duty, and it is not so much a
question whether they have suffered
during that period from those causes
which ultimately weaken and deteriorate
every artificial structure, as whether the
amount of deterioration is accurately
known and provided for. Those who
have read the letter of Mr. Baker, pub-
lished in a daily contemporary not long
since, will be assured that with respect
to both these points, the condition of Ihe
Britannia Bridge is in every way as
satisfactory as when the tubes were first
erected.
Having touched upon the subject of
the corrosion and consequent deteriora-
tion of iron bridges, it may be of interest
to our readers to inquire generally a
little further into the matter. As it is
Vol. XIX.— No. 3—17
with timber, so it is with both cast and
wrought iron. A great deal depends
upon the quality of the material itself,
and the medium which surrounds it.
Some descriptions of timber will last, if
wholly and constantly immersed in
water, practically speaking, for ever.
Timber piles have unquestionably been
found perfectly sound after an immersion
in water of over 500 years. The state-
ment that the piles of Trajan's bridge
were discovered perfectly sound after
the lapse of sixteen centuries, must be
received with caution. Other descrip-
tions of timber will last a long time in a
dry atmosphere, but not when exposed
to damp; and very few indeed will stand
exposure to alternate wetting and dry-
ing. Cast iron, again, has been found,
in one locality, to be so soft after some
years' immersion in salt water, as to be
readily cut with a knife. In another
locality of a similar nature, it has re-
mained for fifteen years as sound as
when first immersed. This case scarcely
applies to the kind of deterioration under
notice, which is limited more particularly
to wrought iron.
The corrosion of wrought iron, to
which structures in the position of the
Britannia tubes are subjected, consists,
practically, in the oxidation of the vari-
ous bars and plates, and of the ironwork
generally of which the tubes are built
up. The oxidation takes the form of
rust or scale, which sometimes falls off,
and at others is removed at the periodi-
cal cleaning and repainting of the iron-
work. Obviously, every successive
formation and removal of this scale di-
minishes the original thickness of the
iron, and it becomes a mere matter of
time until that thickness is reduced to
zero. The remedy, as regards maintain-
ing the strength of a wrought iron
bridge, clearly consists in either prevent-
ing the formation of the scale or allow-
ing for it. No means have yet been dis-
covered which will completely secure the
first of these objects, although much
may be done towards it. It is not diffi-
cult to carry out the latter plan. If the
rate of oxidation for one, or any number
of years, can be ascertained, even with
approximate accuracy, the necessary
extra allowance of material can be easily
provided. It will first be requisite to de-
termine what that rate is, more especially
258
VAN nostrand's engineering magazine.
as it varies with the material employed.
If the medium be damp air, the relative
oxidation of steel, wrought iron, and
cast iron is about 1.12, 1.08, and 0.S4.
It has been inferred from experiments
that the oxidation, or depth of corrosion
of ironwork when exposed to clear sea-
water, increases at the rate of 0.00215
inches of thickness per annum, which is
equal to nearly $fc inches in 100 years,
or to T525¥ inches in 200 years. There is
not any plate in the Britannia tubes
whose destruction would jeopardise the
safety of the bridge which has a thick-
ness less than \ inch or T624g, so that upon
the assumption we have made, the tubes
would, in about 232 years, be entirely
cprroded or rusted away. There is just
one little saving clause in the case,
which might add perhaps another fifty
years or so to their existence — it is that
the scale of oxide might adhere to the
iron, and thus very considerably diminish
the rate of oxidation of the remainder of
the iron.
The Britannia Bridge is placed at an
elevation of about a hundred feet above
the sea level. It is, therefore, apparent
that the supposition that the ironwork
is exposed to the immediate action of sea
water is not correct, and that the tenure
of life assigned to it upon that supposi-
tion is too short. Let us consider the
tubes, then, exposed solely to the action
of rain or fresh water. Under these cir-
cumstances, and making the calculation
from the same datum, the annual depth
of corrosion of the iron will be 0.00035
inches, or at the rate of rather less than
2-f-g- inches in 100 years, or yf^ inches in
200 years. The life of the tubes under
these conditions would be about 1400
years. But this supposition is probably
as much too favorable for the bridge as
the former is unfavorable. The tubes,
although not actually wetted by the salt
water, are, nevertheless, acted upon to
some extent by its saline qualities. They
would be exposed to the action of rain,
which would wash away the rust, and
constantly expose new surfaces for oxi-
dation. Under the most unfavorable cir-
cumstances the bridge would, however,
last at least 100 years. Such a line of
reasoning takes no account, however, of
the conservative powers of paint, which,
if of good quality, and applied with suffi-
cient regularity to surfaces which would
otherwise be denuded, may prolong the
life of an iron structure almost indefi-
nitely. Making all allowances, there-
fore, it is not too much to say that, with
common care, the Britannia Bridge
would last 150 years without any heavy
repairs.
It is well known that the greatest pos-
sible skill and prevision were exercised
in selecting the iron and executing the
workmanship of the Britannia Bridge.
At the same time, it is very possible
that some parts of it are, either from
greater exposure or other causes, more
liable to corrosion than others, and might,
therefore, be sooner deteriorated. In
this case nothing is easier than to cut
out the damaged and weakened plate
and rivet on a fresh one. In fact, the
whole bridge might be gradually repro-
duced piece by piece in this manner
without affecting the integrity of the de-
sign or its practical efficiency. The parts
of the structure most liable to corrosion
are the outside plates composing the
upper and lower booms and the hides,
and these are precisely those which are
the easiest to replace. The complicated
and troublesome portion of the work lies
in the ironwork of the top and bottom
cells. A very recent examination has
proved all the ironwork in these parts of
the tubes to be in a perfectly sound and
unimpaired condition. Experiment has
established one more fact in connection
with the corrosion of iron structures
which is worth mentioning, as it bears
immediately upon our subject. It is that
iron when subjected to repeated vibra-
tion does not corrode with the same
rapidity as when in a constantly quies-
cent state. The number of trains pass-
ing daily and nightly through the Brit-
annia Bridge do not allow it much actual
rest. If to these we add the expansion
and contraction, and the influence of
winds, slight although their effects are,
we doubt if the tubes are ever in a state
perfectly free from vibration. Wrought
iron bridges are comparatively of too
modern a date to afford any reliable in-
formation respecting their ultimate dura-
bility. It will require another fifty years
before the problem will be in a fair way
of being solved, and we may, therefore,
be excused if we decline to say precisely
how many hundred years the Britannia
Bridge will last.
PHENOMENA OF THE COMPASS IN MINING SURVEYS.
• 259
SOME PHENOMENA EXHIBITED BY THE COMPASS IN
MINING SURVEYS.
By WILLIAM LINTERN.
From "Engineering."
The general opinion of the action of
the magnetic needle used to be, and, I
think, generally still is, that, unless di-
verted by purely local and accidental
sources of attraction, and which are,
therefore, removable, the needle will ad-
just itself parallel with the magnetic
meridian of the place and time in all
positions; and that, consequently, when
free to move under such conditions, it
will in a series of different positions
maintain a true parallelism.
Several years ago, having occasion to
make a survey of a certain colliery of
considerably over a mile in length, and
with particular accuracy for a definite
purpose, I first made the survey with
the needle, fixing it to the zero of the in-
strument each time, and working off the
limb, and reading to minutes; I next
made a check survey over the same lines
without using the needle further than to
get the magnetic bearing of the first line,
so as to insure — as I supposed I should
have — the same parallelism as before in
the previous survey; after the first line
I used the instrument simply as an
angleometer by setting the limb with the
precise previous reading back each time
upon the back light, and I simply liber-
ated the needle at each station for the
purpose of observing its action under
those circumstances; and, to my sur-
prise, I soon found such a variation in
the parallelism of the needle, as the
work progressed, that I came to the con-
clusion that an error in manipulating the
instrument had been committed; by re-
observations of the lines I found this was
not the case, and I determined to pro-
ceed again in the same way throughout
the whole length of the survey — in all
over 40 lines — and particularly to watch
the action of the needle.
In the majority of the lines I found a
marked variation of the needle bearing,
and in scarcely two successive positions
would it assume precisely the same
parallelism; sometimes it varied in the
aggregate of a number of lines to as
\ much as 2° 30' on one side of zero, then
j it would gradually return back again to-
wards zero, and then progress to a con-
siderable variation on the other side, —
thus oscillating to and fro several times
: over the zero as the work progressed.
\ The successive angles of the second sur-
vey were reduced on the base of the
I magnetic bearing of the first line, taken
j as before explained, and both surveys
! were carefully plotted off the same
meridian line and position ; and the re-
| suit was that on comparing the two
j series of lines, although there was a
i general agreement in the direction of the
! corresponding parts of the surveys, there
I was yet a distinct minute difference, and
i such was the divergence as the laying
! down of the surveys progressed, that the
I final positions were 120 links apart; and,
taking into account the fact that a
straight line drawn from the initial to
i the final position or station measured 70
chains or thereabouts, the magnetic
J bearing of the first line of the angular
! survey, when compared with the average
| of the readings of * the magnetic survey,
showed that there was an error in one or
the other equal to 59'.
Satisfied that the variations which I
had here so carefully observed were not
the result of what are generally called
removable causes, peculiar to this par-
ticular colliery, I have from time to time
over a number of years, and with differ-
ent instruments, and under a variety of
conditions both on the surface and in
the mines, taken steps to observe the
peculiarities of the working of the mag-
netic needle; and in the result I have
found that a variation, more or less, is
very general — more general indeed than
an accurate parallelism is.
I will here give some examples to
show this variation more forcibly.
Ex. 1. — In a heading crossing the pitch
of the strata from one vein of coal to an-
other (technically called aacross-meas
ures" heading), a straight line was care-
fully ranged out, and at nearly equal
260
VAN NOSTRAND's ENGINEERING MAGAZINE.
distances apart, over a total length of
about 60 yards, the instrument was set
up five times in correct alignment, and
the magnetic bearing of the lights pur-
posely fixed at the two ends of the line
were observed from each position; and
the result was, that what is generally
supposed would have been five similar
readings, turned out to be as follows,
viz., 174° 3', 175° 21', 174° 45', 172° 30',
and 174° 40', thus indicating a maxi-
mum variation equal to 2° 51' in a line
not more than 60 yards in length.
Ex. 2. — In a heading driven in a vein
of coal 4 feet thick, and into and through
a piece of faulty ground, consisting
mainly of a mixture of rock and cliff, a
line of about 60 yards in length was
ranged out as before, and the instrument
fixed first at that end of the line away
from the "fault," and the light observed
and read at the other end of the line
within the faulty ground; seven other
positions were then fixed upon in correct
alignment in succession towards the
other end, and the readings taken at
each, and the result was the following
series, viz., 36° 24' 36° 20', 37° 50', 38°
15', 39° 40', 39° 10', 38° 10', and 37° 0',
in this case indicating a maximum va-
riation equal to 3° 20'.
The line of the " fault " crossing the
alignment of the several positions was
an acute angle, and the sixth reading
was about in the line of its crossing, and
the seventh and eighth readings w^re
within the fault.
By referring to the several readings it
will be observed that there was an in-
creasing divergence in the same direc-
tion (to the right) in approaching the
fault, and that after entering the fault
there was a sudden twist back again in
the contrary direction.
Ex. 3. — A series of magnetic bearings
was taken in an engine plane under-
ground, which was driven quite straight
from end to end, and the bearings were
taken previously to the setting up of the
ordinary fixtures of an engine plane,
which usually interfere with surveying
operations prejudicially; and over a
length of about 330 yards the following
readings were accurately observed, viz.,
346° 55', 345° 0', 346° 42', 346° 15', 345°
0', 346° 30', 34i>° 9', 345° 48', and 347°
3', thus showing a maximum difference
equal to 2° 3'.
Repeated trials on carefully ranged
out surface lines do not indicate the prev-
alence of so great a variation of mag-
netic readings as underground lines, but
even these show frequently a marked
variation. The following examples* are
given as evidence of this :
Ex. 4. — On a surface line of about
thirty chains in length the instrument
was set up five times in correct align-
ment, and observations taken, and in this
particular example the readings at each
position corresponded precisely with all
the others.
From one end of the previous line, and
almost at right-angles with it, another
line of about twenty. four chains was
ranged out in the same manner as before,
and the following series of readings
taken :
Ex. 5.-54° 58', 54° 51', 54° 44' and
54° 58'; these therefore almost indicate
a much less variation than in the lines
underground.
Ex. 6. — In a long carefully ranged base
line of a surface survey of considerable
extent several observations were taken as
at other times, and the following were
among the readings taken down, viz.:
114° 41', 114° 41', 115° 7', 115° 21',
showing in these a maximum variation
of 40'. This variation, although it does
not look so formidable as some of the
previous ones given, yet, when analyzed,
it represents something serious ; for if
viewed in reference to the length of that
section of the line, at the extremities of
which the instrument was set up and the
readings taken — in one case 40 chains,
and in another 26.45 chains — we shall
find that in the former case the twist of
position due to the variation (and conse-
quently the error that might have been
thus imported into the work), is equal to
46.5 links, and in the other case it is
equal to 30.7 links; and this is a conse-
quence scarcely to be neglected or over-
looked.
The foregoing examples, confirmed by
many other observations made from time
to time, plainly indicate that the mag-
netic needle does not — even when used
on the earth's surface— maintain gener-
ally an accurate parallelism, and that
when used in underground operations
the variations are generally much more
marked.
This subject has, of course, a primary
PHENOMENA OF THE COMPASS IN MINING SURVEYS.
261
bearing upon the use of the magnetic
needle in surveying operations; but it
has often occurred to me that this effect
of the ceaseless operation of magnetic
forces may not be, and most probably
is not, the sole and only consequence of
manifestation to us.
What the intrinsic change really is
which a piece of steel undergoes in the
process of being magnetized, and con-
verted into a magnetic needle, I have
never been able to understand to my own
satisfaction; but my observations lead
me to suppose that whatever the internal
change may be upon the steel, it results
externally in imparting to the needle
the power to conform to the direction of
the current of magnetic force passing
around it at the moment, and in the
position in which it is being used.
I have often observed on different
occasions that the needle seems to be
more deflected from its true parallelism
when used in close proximity to faulty
and disturbed ground, and also when
used in headings passing through such
varying ground as is met with in what
K is technically known as " crossing the
measures," than in ground of a more
uniform nature, whether it be an iron-
stone mine or a coal mine; and the con-
clusion I arrive at in view of these ex-
periences and circumstances is, that the
needle deflections represent the deflec-
tions of the passing current of magnetism
in the surrounding strata, and that these
deflections of the current are again the
result of the varying powers of con-
duction possessed by the varying strata
of the earth; that, in fact, as water
turns aside from the more confined parts
of its channel to that which affords it
the freest passage, so does the magnetic
current get slightly deflected, first to
one side, and then to the other, in its
passage through the strata, the best con-
ductor conveying the greater quantity;
and when this superior conductor comes
to an abrupt end, or becomes distorted
or disturbed, either from a " fault," or
from some other cause, the current be-
comes more or less deflected, and the
magnetic needle used in close proximity
to such a position, or locality, would
also in its turn become deflected in
sympathy with the current.
But I conceive that there is a great
probability that this same subtle power
frequently operates to the causing of
j other consequences, which are often not
a little perplexing to account for, and to
understand.
In that state of the weather when the
j atmosphere is highly charged with elec-
| tricity, and heavy storms of rain are
I frequent, we often experience the spring-
ing up of a sudden wind, which, leading
in the van, as it were, as well as bring-
ing up the rear of the disturbed elements,
blows furiously for a while until the rain
has ceased, when the wind again gradu-
ally subsides into a perfect calm. To
my mind the theory that winds are
caused by the rarefaction of the atmos-
phere in certain localities, to which the
air rushes to restore the equilibrium —
thus causing winds — utterly fails to
afford a sufficient and satisfactory ex-
planation of the occurrence of these
suddenly springing up and as suddenly
subsiding winds, carrying, as they seem
to do, a furious storm of rain, or hail, or
snow in their bosom.
But whatever may be the intrinsic
nature of the force put into operation,
whether electricity striking out abnor-
mally (if such an expression may be per-
mitted) in a deflected line or otherwise,
it is certain that the vis viva of the
power thus set in motion represents an
enormous aggregate of force, as the
destruction sometimes wrought by a
small portion of it sufficiently attests.
Disasters, sudden and startling, some-
times occur in collieries from the explo-
sion of gas; and the only explanation
frequently possible is, that a sudden out-
burst of gas has occurred and over-
powered the ventilation, and that from
a defective lamp, or from an unprotected
light, the gas exploded; and we not un-
frequently find the sudden outburst of
gas explained and accounted for by say-
ing that a "fall of roof" took place.
Now I am strongly of opinion that
where these two things are found to
have occurred together, they are not
necessarily, nor obviously, cause and
effect in the order named, but that, much
more probably, if they are not two
effects of the same cause, the fall of
roof is a consequence of the explosion.
When a vein of coal has been ex-
tracted from its position in the strata
over a considerable area, the roof, or the
floor, or both, will be sure, sooner or
262
VAN NOSTRAND S ENGINEERING MAGAZINE.
later, depending upon their natural and
also their relative strength, to show a
tendency to close up the space from
which the vein of coal has been ex-
tracted; if the strata in which the coal
lies is of a friable nature, and readily
breaks up, the large interstices resulting
from its closing up the space formerly
occupied by the coal will necessarily be
much more ramified throughout the
broken strata, but will not form one or
two large chambers; if, on the other
hand, the strata is of a more tenacious
nature, and will bear a very considerable
subsidence or elevation before it will
break up, then a chamber more or less
large, either in the back of the subsidence
or beneath the upheaval, or both, will
necessarily be the result.
These ramifying intervening spaces as
in the first case, or the more extensive
chambers as in the second case, will not
be in vacuum, but will become filled
with the air or gas, or a mixture of both,
so fast as they are formed ; if the strata
give off carburetted hydrogen gas, then
it may be taken for certain that an ex-
plosive mixture will very soou, by reason
of the operation of the law of diffusion
of gases, occupy the whole of the spaces
and chambers so formed.
Let us now assume the occurrence of
quickened activity in the earth-currents
•in our latitudes as are so frequently,
though more forcibly, experienced in
some other parts of the world (and
which, when they are atmospheric, we
have such sensible and frequent experi-
ence of), and we shall not be assuming
too much if we credit those earth-cur-
rents with a very largely increased vis
viva under such circumstances; let, then,
such chambers as are mentioned above,
and filled with an explosive mixture of
gas, lie in the path of such earth-cur-
rents, and their vis viva will immediate-
ly tell upon a body so imponderable, and
such an impulse would be imparted to it
as would immediately drive a considera-
ble portion of it through the joints of
the ground communicating with the coal
workings, and if a naked light or a de-
fective lamp should be within its reach
an explosion would be certain to ensue;
and once a portion of it became ignited,
the explosion would extend to wherever
the train of the gas in the requisite
mixed proportions extended, even to the
partially emptied chambers of the roof
or floor ; and where such happens the
strongest roof must give way and be
blown down, seeing that the expansive
energy of such gas immediately after ex-
plosion is about five atmospheres, or 75
lbs. per square inch. And hence I con-
sider it much more probable that the
" fall of roof " is the result of the explo-
sion instead of its being an antecedent
consequence of it, and contributing in
that sense to bring it about.
A friable roof and floor may, also, in
this view, from the fact of its more read-
ily breaking up, and thus preventing the
accumulation of so large a lodgment of
gas in a single chamber, and also by fa-
cilitating the more continuous drainage
of the gas into the passing air of the
mines, render the colliery far less subject
to sudden outbursts of explosive gas
than a mine with a much stronger and
more tenacious surrounding strata would
be; and thus, on the whole, the former
would be more safe from that class of
accident than the latter.
I cannot deny of course that some of
the opinions I have expressed here, and
some of the conclusions I have drawn
from them, may possibly be characterized
as being insufficiently supported by my
premises; the existence, however, of such
magnetic variations as I have here de-
monstrated, and the known fact of the
existence of those powerful earth-cur-
rents that make their presence and power
felt so forcibly in some other parts of
the world; and also remembering those
atmospheric disturbances which are so
universally felt at times in all parts of
the world — these appear to me to justify
such a train of reasoning as that I have
here entered into; and if what I have
here written should lead to investigations
tiy abler hands than mine, from which
good may ensue, and our knowledge of
these things become more extended, I
shall be as much gratified as any one else
can be.
*<&&•
In an interesting paper lately read at a
meeting of the Royal Society, on " Ex-
perimental Researches on the Tempera-
ture of the Head," Dr. Lambard showed
that mental activity will at once raise
the temperature of the head, and that
merely to excite the attention has the
same effect in a less degree.
CLEOPATRA S NEEDLE AND ITS WORKMEN.
263
CLEOPATRA'S NEEDLE AND ITS WORKMEN.
From "The Builder."
We have had the opportunity of care-
fully inspecting the now familiar Cleopa-
tra's Needle. It has been exposed
partially to public view, and a little at
least can be readily seen from the
Embankment. We call attention to it
now, and while it is in its present bond-
fide state, as it is while in that state that
such a monument is really and truly in-
teresting to the lover of past' art and
methods of workmanship. So much
indeed, — may we not say everything? —
round and about us of our own antiqui-
ties has changed and been modernized,
that a glauce, — as here, — at a genuine
"antiquity," in its rough and time-worn
state, is quite a novelty, — a something
really strange to see, and leaving an im-
pression not to be got at in any other
way. The preparatory work, it may be
mentioned, of providing a pedestal for it
to stand on is rapidly progressing; and
it is earnestly to be hoped that this too
elaborate pedestal will not dwarf, and
make quite secondary, the monolith
itself. We here propose to make note
of it as it now is, and while it tells so
simply its own story, and to call attention
to the workman's part in the granite
cutting and carving of it, and which, to
say truth, needs no added work to make
it attractive.
So many descriptions and accounts of |
this "Needle" have been already given
that it must needs be familiar to most,
but there are yet one or two things con-
nected with it which have been hardly j
noticed; but they are vital elements in
the matter notwithstanding. A word or
two, then, may at the present juncture
prove useful. We are told in an authori- 1
tative book on Egyptian history and
antiquities, that of all works of Egyptian
art in simplicity of form — we ask note
of this — colossal size, and unity and
beauty of sculptured decoration, none
can be put in comparison with the
obelisks. The Caesars of Rome vied
with the Pharaohs of Egypt in their
admiration of the obelisks, but it is not
said that these same obelisks were put
up in the places where they were found,
because they were pretty to look at, or
as attractive monuments; they were,
indeed, and simply, pieces of the temple
furniture, just as much so as any item of
church furniture is a thing of use and
necessity in a church of to-day. Obelisks
never stood alone and isolated as this
one on the Thames Embankment is to
stand, but always in pairs, and imme-
diately in front of some building or
pylon; so that in approaching them,
and getting sight of them, they were
seen detailed against the huge mass of
walling near which they stood, and were
thus seen at their very best, their long
shadows being all but a part of them.
The use and origin of the obelisk is yet
as debateable as ever, and why these
were placed at the entrance of the great
temples, and always in pairs, is not ap-
parent, and whether or no any pause or
ceremony took place on the occasion of
the long procession when passing be-
tween them into the Temple is not
known, and can be only conjectured.
All that we do know is, and of this we
may feel quite sure, that they were not
cut out from the quarry, and brought to
their places, at such a vast cost of labor,
for the mere sake of putting a something
in the places where they stood, but that
they had a peculiar and highly signifi-
cant meaning, and were, indeed, essen-
tial parts of the Temple apparatus,
whatever that might have been. It may
be that, could we be quite sure of the
hieroglyphic reading, this would be ex-
plained. Objects so conspicuous and so
striking must need have been highly
symbolical in purport, and must have
been as open books to be read in the
passing by them. This absence of a
building, of which the obelisk formed a
part, and the fact of the ever-present but
mysterious writing on it, would startle
the old Egyptian builders and workmen
not a little, could they but return for a
brief moment, to look at their work or
our river Embankment.
But our object at present is not to go
into the history, and even uses, of the
obelisk, but to make note of its artistic
264
VAN NOSTRAND'S ENGINEERING MAGAZINE.
character, and of the cutting of the
hieroglyphics on its huge surface. We
have examined this with some attention,
and would recommend the study of it to
our stone-carvers. The actual material
out of which this monolith is cut is hard
granite, and right good tools and skillful
hands only could have made impression
on it. This granite-cutting is remarkable
in many ways. It is not simply the
carving out of the hard and intractable
substance the forms we see, but the
indications of manner which are to be
noted in the doing of it. Large, and ap-
parently rough, as the granite-cutting is,
there is the constant presence of the
artist workman to be seen in it. The
surfaces are not all of a uniformly dull
flatness, as such work would now be
made, and as it is done when "lettering"
is cut out of stone; but a thorough
knowledge of the form and even life of
the object represented is here, when such
object admits of it. We would here ask
^the attention of those who have to do
with such specimens of the workmanship
of so long a bygone day to note this, so
that no attempt whatever may be made
at "re-cutting," or mending, or "restor-
ing," as it would be called, of the work,
or even repolishing it. If this be done,
all the antique life of work goes. We
hear that this is under consideration,
but if so, before it is done, may we sug-
gest casts of the hieroglyphics, and thus
that, at least, a true record be preserved
of them.
These hieroglyphics should be studied
while the obelisk is where it now is, on a
level with the eye. One thing, by the
way, little as we know about the matter,
was intended by those who erected
obelisks, and that was that they should
be as ever-open books, to be readily antf
easily read, they always standing on a
low block of granite, so as to admit of
this. The letters were close to the eye
as could be, and even when near the top
of the monolith were so large, and so
deeply incised, that they could be readily
read from top to bottom. Indeed, the
longer this magnificent granite cutting is
looked at, the more do you wonder at it,
and at the skill with which it is done.
In the clear sunlight of Egypt these
hieroglyphs show themselves with an
almost startling precision and distinct-
ness. The old Roman was justly proud
of his lettering on his buildings, and
right well he did it, but it quite pales
before such works as this, where the
forms even admit of vitality in the ren-
dering of them. Again, then, may we
express a hope that they will not be tam-
pered with, but left as the antique car-
vers cut them, and no attempt made to
"polish" or recut them, or, indeed, in
any other way to destroy or mar their
individuality and antique expression.
We are here looking at this huge
monolith as a specimen of the work that
in its time was done in Egypt, and we
cannot but wonder at the power of such
work, when contrasted with what is now
possible. Compare the mechanical ap-
pliances then and now, and well may we
wonder at the skill and patience of the
old Egyptian quarrymen and granite-
cutters, who managed to subdue even
this huge mass, and to cut it out of its
natural bed, and to afterwards move it
into its place. Nothing, indeed, would
seem to have been too huge for the
Egyptian workmen; blocks, however
large and weighty, were quarried and
moved long distances, and then set up
with an ease and skill which might appal
even our mechanical and steam-aided
powers. Indeed, we hardly know which
to wonder at most, the power displayed
by the old workmen in the cutting out
and the moving of such huge masses of
so hard and solid material, or at the artis-
tic skill and feeling afterward displayed
in the "ornamenting" of them. We
have much to learn even in these ad-
vanced days, and but few able to doubt it ;
but if any do so, why here is a proof in
point, and he who runs may here read.
We do not intend just now to say a
word on the pedestal, out would remind
lovers of genuine antiquity that those
who designed this monolith never
dreamed of anything of the sort threat-
ened !
It is impossible to make note, however
slightly, of this really magnificent ex-
ample of the skill and artistic power of
the w7orking artists of Egypt without an
earnest hope that no attempt will be
made to add to it anything that can be
avoided.
It may here be of interest to mention
that an Arab writer, in the twelfth cen-
tury, notes that the obelisks had even
in his day "copper caps" on their tops;
Cleopatra's needle and its workmen.
265
but these without doubt, he hints, were
after-additions by those who had con-
quered the country. Our object now
should, as we think, be to preserve this
monument as an Egyptian antique, and
as one purely and solely Egyptian, and
thus to' see it, as they of Eorypt of old
saw it, in all its simplicity and harmony
of outline and strength of granite cut-
ting. An obelisk is in itself so simple
an object that it is impossible to add to
it without, at the same time, taking away
from it. Like a Stonehenge block, it can
not be added to without injury.
HOW IT IS TO BE ERECTED.
The cylinder and its contents having
been floated some three or four weeks
ago over the temporary gridiron made to
receive it on the up or Westminster side
of the Adelphi Stairs, was, before being
allowed to permanently rest on the grid-
iron, canted over on one side by the sim-
ple expedient of shifting the ballast. As
canted over, the bottom of the vessel
faced the Victoria Embankment, while
the upper or deck side faced the Surrey
shore. The vessel was canted over in
order that that side of the monolith which
is least " weathered," or, in other words,
which retains the most sharply-cut hiero-
glyphics, should be parallel with and
face the Embankment roadway. The
side which will face the river is the most
weathered of all, the remaining two
sides, which will be at right angles to
the Embankment roadway, being not so
much worn. The vessel having been
canted over, the first thing to be done
was to begin pulling it to pieces. Near-
ly all the iron plates were removed, the
ribs remaining intact, and the obelisk,
wedged up from the gridiron, remained
submerged at high tide. During low
tide the obelisk, which has its point or
pyramidion in the direction of Waterloo
Bridge, has been slowly moved forward
by means of hydraulic jacks, until, at
the time of writing, the obelisk has
emerged, point foremost, a considerable
distance out of its iron shell, the apex
nearly touching the stairs on the up or
Westminster side. The next, operation
will be to raise the obelisk bodily to a
height sufficient to clear, and to allow of
its being traversed partially over, the
landing between the two flights of stairs.
When the obelisk has been centrally
placed over this landing, it will be again
raised to a height just sufficient to clear
the two masses of granite (part of the
Embankment structure) which will flank
the obelisk when erected, and which
masses it is proposed to surmount with
sphinxes. Having attained this height,
it will be moved laterally towards the
Embankment roadway until it lies across
the center of each of the flanking masses
or pedestals of granite referred to. The
obelisk will be moved in all cases by
means of hydraulic jacks, and carefully
" packed " as the work proceeds, so as to
prevent undue strains upon it. The obe-
lisk having been got into the position in-
dicated, i.e., lying horizontally across
the spot upon which it will stand, will
be cased in its central portion with a
wrought-iron jacket, about twenty feet
long, and riveted at the angles. This
jacket will be made to fit pretty tightly
by means of wedges of* wood, and in
order to prevent the stone from slipping
out of this jacket a wrought-iron strap
will be carried round from side to side
under the foot of the obelisk. This
jacket, which wills weigh about 16 tons
(making, with the obelisk, which weighs
about 186 tons, a total of about 200
tons), will be fitted with strong projec-
tions or trunnions on the two sides fa-
cing the Embankment roadway and the
river respectively, and these trunnions
will rest upon two specially -made
wrought-iron girders lying parallel with
the obelisk itself. Each of these girders
will be raised at each end by means of a
hydraulic jack, and will work in and be
guided by the recesses left in each of the
four main uprights of the specially-de-
signed scaffolding which will then have
to be erected. Roughly speaking, these
four uprights will form the corner bound-
aries of an oblong space 17 feet by 8
feet 6 inches, the two longer sides being
parallel with the obelisk and spanned by
the girders before mentioned, and the
obelisk projecting for about a third of
its length beyond each of the shorter
sides of the imaginary oblong described
by the four uprights. These uprights
will be about fifty feet high, and will
each consist of six " sticks ,y of timber,
twelve inches square, arranged and bolt-
ed together three and three, parallel with
the obelisk, with a space nineteen inches
wide between each six for the ends of
the girders to work in.
266
VAN NOSTRAND'S ENGINEERING MAGAZINE.
These uprights will, of course, be
thoroughly braced together and stayed
and gtrengthed by raking struts, &c.
Each end of each girder will be simul-
taneously raised and "packed," until the
girders, supporting the obelisk in a hori-
zontal position by means of the trun-
nions of the iron jacket before described,
shall have attained a sufficient height to
allow of the whole mass being swung
round on its trunnions, so that its base
shall be but a short distance higher than
the pedestal prepared for it, when, all
being right, it will be gently lowered to
its position. The pedestal, we may say,
will rest on a foundation of Portland ce-
ment concrete, carried down to a depth
of forty feet to the London clay. This
part of the work has been executed by
the Metropolitan Board of Works, for
and at the cost of Mr. Dixon. The pe-
destal itself will be of hard bricks, set in
Portland cement, and faced with blocks
of gray granite (the same as that used
for the Embankment wall) of consider-
able size. Of this pedestal a portion has
been already erected, but the remainder
will have to be built up after the obelisk
has been raised, by the means described,
above the highest course of the pedes-
tal. A shallow groove will be provided
on the top, in order to allow of the re-
moval of the wrought-iron strap, already
mentioned. Although the four corners
of the lower part of the obelisk are very
much abraded, there still remain about
twenty-four superficial feet of flat sur-
face at the bottom, and this extent of
bearing surface will, it is believed, be
fully sufficient to insure stability.
We believe that nothing is definitely
decided as to the proposed sphinxes; but
we may note that, in the " Visitor's
Book," a gentleman has put on record
the substance of a conversation he had
with the late Mr. Joseph Bonomi, who
expressed the opinion that, if sphinxes
ai^ to flank the obelisk, they should be
of a date coeval with that of the obelisk
itself. Mr. Bonomi only knew of two
such sphinxes — one in the National Col-
lection at Paris, and another in the Duke
of Northumberland's collection at Aln-
wick— and he suggested that one of these
should be adopted as the model of those
which it is proposed to place in juxta-
position with the obelisk.
The work of getting the obelisk into
position must necessarily proceed slowly.
It is hoped, however, that the work will
be safely effected by the end of August.
PROBLEM FOR ROLLING STOCK AND RAILWAY BUILDERS.
From "Iron."
Our English railway system is, beyond
question, the most complete that exists.
Nowhere else are such facilities enjoyed
for reaching any desired point, and in
the matter of high speed we lead by
great lengths. Still we are far off per-
fection, and, indeed, in many minor re-
spects our Continental and transatlantic
neighbors excel us. One of these is the
attention paid to the comfort of passen-
gers; another, the better training in
courteous bearing of officials; and others
will readily suggest themselves to any
who have had opportunities of institut-
ing comparisons. One drawback to rail-
way journeys in England is the swing-
ing from side to side of the carriages.
This is not a defect peculiar to us. It is
no more guarded against across the
Channel or in the United States than
here. But in England we suffer more
from the annoyance, because express
riding is popular; and the measure of
carriage oscillation much depends on the
velocity of travel. The swinging and'
jerking incident to a ride of a hundred
miles or so in an express train enervate
and distress travelers, and, whatever the
demands upon them, effectually bar the
weak or invalid from so voyaging. The
drawbacks are so manifest as to make it
not a little remarkable that builders of
permanent way and of rolling stock have
not long since devised means to remedy
them. The " Bogie " principle . was
evolved to meet the difficulty, and has
contributed fairly to that end, we believe ;
but even that — and it can only be re-
PROBLEM FOR ROLLING STOCK AND RAILWAY BUILDERS.
267
garded as much less than what may be
accomplished — has not been taken kindly
to by railway corporations. The Mid-
land is the only large company which
has even partially adopted it. Proba-
bly the lack of remedy is traceable to
absence of demand. We grumble at in-
conveniences long before we clamor, and
it is only clamor that can wring conces-
sions from railway owners, whom we
are pleased to regard as the servants of
the public, but who treat the public as
farmers do their turnips — make as much
out of them as they can with the least
outlay. Sotto voce protest has now,
however, ended, and agitation has begun.
It is a singular fact that during the
whole fifty years since railways were
first introduced there has been no im-
provement in the wheel and axle arrange-
ment, and the rigid fixture of the wheels
now is just the same as Mr. George
Stephenson adopted, and, indeed, found
adopted when as a boy he saw them at
work in the collieries of Durham. Two
wheels are practically welded to a bar
of iron, and neither of them can move
without the other, so that in passing
over a curved line of railway which has
two rails of different lengths one of them
must travel over a longer space than the
other. In order to modify the natural
action of these opposing conditions, the
outer, or longer rail, is "banked up,"
and thus the perpendicular line of the
load is changed, and the "grind" is pro-
duced by the flange rubbing against the
rail; and it is owing to this action that
so many train accidents happen of
vehicles leaving the line. One of the
wheels must " skid " more or less, and
friction is thereby very much increased,
the "wear and tear" of both the wheels
and the permanent way is largely aug-
mented, and so is the danger. An inter-
esting correspondence is now going-
forward in The Times touching this
matter. It was initiated by Mr. James
Howard, who having, during two jour-
neys to the Paris Exhibition, been keenly
annoyed, was prompted to ask, " Have
railway companies in England kept pace
with the general advance?" Replying
to his own query, he says: "If this
question were to be answered from the
experience gained upon the South-East-
ern, and London, Chatham and Dover
lines, it would, I think, have to be
answered in the negative: on the con-
trary, if answered from experience of the
Midland Railway — upon which I iteside,
and upon which many improvements
have been adopted — it would, unques-
tionably, be answered in the affirmative.
About a month ago I came to Paris, and
chose the London, Chatham and Dover
line, but owing to the oscillation of the
carriage being so violent and alarming
to myself and fellow passengers, I deter-
mined to try the South-Eastern route, and
left London by the 9.25 p.m. train for
Folkestone. Bad as was the former line,
portions of the South-Eastern if any-
thing were worse; the oscillation was so
violent just before reaching Sevenoaks
that, upon the train pulling up at that
station, I left my carriage to speak to
the guard. Upon saying to him there
would be accident before long unless
some improvements were made in the
road we had just passed over, he re-
marked that for such high speeds this
portion was bad. I do not want to en-
danger the lives of such valuable public
servants as Colonel Tyler or Colonel
Rich, but am persuaded if either were to
take a trip on these two lines at express
speed he would come to the conclusion
that improvements were imperatively
called for. I hope to see, at no distant
date, engines and carriages upon the
'Bogie' principle universally adopted, as
well as simultaneous, automatic brakes;
they work admirably on the Midland.
Time of course must be allowed for the
wearing out or conversion of the existing
rolling stock, but in respect of perma-
nent ways, surely railway companies are
bound by every moral consideration to
maintain them in the highest possible con-
dition; to alarm their passengers in the
way Ihave described through failure so to
maintain them is, to say the least, unpar-
donable. To feel that your carriage, being
propelled at forty or fifty miles an hour,
cannot keep the rails with so much sway-
ing and bumping is a trial even those
with the strongest nerves do not care to
have repeated." Mr. Francis W. Dean,
tutor in engineering at Harvard Univer-
sity, U. S. A., has also taken part in the
correspondence. He says he has noticed
on nearly every railway he has traveled
on in Great Britain the same defects of
which Mr. Howard makes complaint and
endorses what he says touching the value
268
VAN nostkand's engineering magazine.
of the " Bogie " system as a remedy.
This system, he adds, has further to rec-
ommend it the fact that it .prevents the
grinding of the flanges on the rails. In
support of the latter proposition he
writes :
"Although I have had an opinion
upon this matter for an indefinite
time, at York, the other evening, I be-
came convinced that the amount of the
grinding is not over-estimated by advo-
cates of the Bogie system. While wait-
ing at the station in that place, I heard
.squeaking between the flanges and
1 metals,' which far exceeded anything
that I had ever anticipated. The loco-
motives were noble specimens, and be-
longed chiefly, if not wholly, to the
North-Eastern Company. As the Aus-
tralian commissioner, Mr. Higinbotham,
in his report of the railways of the world,
has substantially remarked, such locomo-
tives and carriages would hardly keep on
the rails on less perfectly permanent
ways than those in Great Britain. I may
remark that I have traveled in both the
Bogie and common carriages of the Mid-
land Company, and found the difference
very striking." The gravity of the de-
fect animadverted on is palpable and the
necessity for removing it obvious : and
there are few save railroad proprietors
who will not agree that should the adop-
tion of the " Bogie," or any other remedy,
ensue from the correspondence, a service
will have been done the public by Mr.
Howard and those who have with him
participated in it.
STEEL PLATES AND RIVETED JOINTS.
From "Engineering."
A circumstance connected with the
greater ductility of soft steel compared
with that of iron plates, which appears
to us to require consideration, is the
effect of this greater ductility upon the
crippling strength of the plate, and con-
sequently upon the proper proportions of
the riveted joint. The softer and more
ductile the plates the more liable is the
material at that side of the hole that
bears the stress to be crushed or crippled
by the rivet bearing against it.
With iron plates and iron rivets, in
order that the tearing, shearing, and
bearing resistances may be theoretically
equal in single riveted lap joints, if we
take the thickness of the plate as unity,
and assume the tearing stress to be
equally distributed over the section of
the plate between the holes, and the
plate to receive no damage by punching
the thickness of the plate, mean diameter
of hole and pitch of rivets will be repre-
sented by the numbers 1, 2.6, and 7.6,
the efficiency of the joint or the ratio of
the strength of the joint to that of the
solid plate being 0.66. As the diameter
of the rivet holes in £ inch plates seldom
in practice exceeds twice the thickness,
and the pitch 4J times the thickness of
the plate, it is evident there is an excess
of bearing strength over both the tear-
ing and shearing strength in £ inch
plates with the usual proportions of
joint, and this excess increases with the
thickness of the plates, taking the diam-
eter and pitch of rivets generally used.
With double-riveted lap joints tak-
ing the thickness of the plate as unity,
we should have the thickness of plate,
diameter of hole, and pitch of rivet
represented by 1, 2.6, and 12.75. In
practice, the pitch in ^ inch plates
double riveted seldom exceeds seven
times the thickness, and three and a half
times the thickness in 1 inch plates, so
that the excess of the bearing over the
tearing strength is even greater than in
single riveting, the excess over the
shearing strength remaining the same.
In reducing the thickness of plate
when substituting steel for iron plates
by the amount allowed by the excess of
tenacity of the former over that of the
latter, or, say, by 25 per cent, if we re-
tain the same pitch and diameter of
rivets, we shall maintain the same pro-
portion of tensile and shearing strength
in the plates and rivets, neglecting, for
the present, in the case of lap joints the
increase in the proportion of strength
due to the stress being less out of line at
STEEL PLATES AND KIVETED JOINTS.
269
the overlap of the thinner plates of steel.
The bearing surface of the plate will,
however, be reduced by 25 per cent. If
the resistance of soft steel to crippling
were greater than that of iron, in the
same proportion that the tenacity is
greater, the redaction of bearing surface
would be compensated for by the great-
er resistance to crippling. As, however,
the ductility of soft steel is considerably
greater than that of ordinary iron plates,
it is extremely probable that the resist-
ance to crushing is less. The resistance
to crippling no doubt varies widely in
different qualities of iron plate, but com-
paratively little is known of this resist-
ance in iron and still less of that in steel
plates. From the results of the few
experiments that have been made with a
view to ascertain its value for iron it is
usually taken at twice the tensile strength
of ordinary boiler plates.
If we take the tenacity of steel as
being one-third greater than that of iron,
which allows a reduction in thickness of
25 per cent, only, and assume the resist-
ance to crushing as being 25 per cent,
less, in order to compare the proportions
of joint for equal tearing, shearing, and
bearing resistance, we shall have, using
the same mode of comparison as above,
1, 2, and 4.4 representing the thickness
of plate, diameter and pitch of rivets for
single-riveted lap joints in steel, and 1,
2, and 6.8 for double riveting, giving an
efficiency of .54 and .70 respectively.
These theoretical proportions of joints
are much nearer what is used in practice
than is the case with iron plates. In re-
placing -|--inch iron plates with |-inch
steel plates, and using f -inch rivets at
lf-inch centres for single and 2|-inch
centres for double riveting, we shall
have a joint with the tearing, shearing,
and bearing resistances all equal. In re-
placing a I -inch iron plate by a J-inch
steel plate, we should require lj-inch
iron rivets at 3J inch centres for single
and at 5-inch centres for double rivet-
ing in order to have a theoretically pro-
portioned joint, and by using 1 J-inch
rivets at 2|--inch and 3|-inch centres re-
spectively for single and double riveting,
it is evident we shall have an excess of
bearing resistance over that for tearing
and shearing.
In the report of Lloyd's Registry
Committee on steel for boiler making it
is stated that in consequence of the crip-
pling of the material behind the rivets in
some experiments, it appears that a great-
er proportion of bearing surface is re-
quired with steel than with iron. Un-
fortunately the dimensions of the joint
that thus failed are not given.
There are two ways of bringing up
the bearing- surface, (1) by increasing
the diameter of the rivets, and (2) by
increasing the number of rivets. By
increasing the diameter of rivets and
maintaining the same pitch, we diminish
the efficiency of the joint, and if we
attempt to increase the pitch in order to
maintain this efficiency, we neutralize
the very advantage sought in increasing
the diameter of rivets. It must not,
however, be forgotten that by increasing
the diameter of rivets without altering
the pitch, we may increase the propor-
tion of bearing surface by a much great-
er amount than we reduce the proportion
of tearing section. For instance, by al-
tering 1-inch rivets at 3j-inch centres to
1 1 inch rivets, we increase the bearing
surface by 50 per cent, whilst we reduce
the shearing section 20 per cent. only.
In all cases it must be a question wheth-
er the increased bearing strength obtain-
ed by increasing the diameter of rivets
is wisely bought at the expense of the
efficiency of the joint. Whether we
maintain the same pitch or not, we give
a preponderating shearing strength to
the rivets, by increasing their diameter
beyond the usual practice for iron plates.
In seeking to obtain additional bearing
surface by increasing the number of
rivets in the same line and reducing their
diameter, we reduce the tearing strength
to the same extent as by increasing the
diameter and maintaining the number of
rivets. In this case we injure the plate
more by punching, but the stress will be
more evenly distributed over the plate,
and we get a joint that is more easily
made and kept tight if the rivets are not
made unduly small. Here again the
proportion of tearing section is not so
rapidly reduced as that of the bearing
surface is increased. Suppose we replace
1-inch rivet holes at 3 J-inch centres
by f -inch rivets at lf-inch centres, the
bearing surface will be increased 50 per-
cent, and the tearing section diminished
20 per cent., the shearing section being
increased about 12 percent.; or by using
270
VAN NOSTRAND'S ENGINEERING MAGAZINE.
^-inch holes at 2|-inch centres, the bear-
ing surface will be increased 16.6 per
cent., whilst the tearing section will be
reduced 6.6 per cent. only. When ad-
ditional bearing surface is actually
required, it is best obtained by making
an additional row of rivets in the joint.
The carrying out of the recommenda-
tion to increase the diameter of rivets!
when substituting steel for iron plates |
may easily be pushed too far, and count-
eract some of the benefit we should ex-
pect to derive from the superior ductility
of steel. If all rivet holes were drilled
fair with the plates in position and close
together, and if every hole were filled by
its rivet to make a perfect job, in which
each rivet takes its share of the stress
distributed over the length of the joint,
it would even in this case be scarcely
advisable to proportion the joint so as to
bring the crippling strength up to the
tearing strength of the plate, for it is
much better that the holes should elon-
gate by crippling under severe stress,
such as that caused by unequal and sud-
den contraction, and give warning by
leakage, which might not require the
renewal of the plates to render the boil-
er serviceable, than that attention should
be drawn to the presence of the strain-
ing by the fracture of the plate from
hole to hole, which is always a serious if
not dangerous defect requiring partial or
complete renewal of the plate, and which
may occur without giving warning,
through the crippling strength of the
plate being kept too high.
When we increase the size of the
rivets, we increase the bearing surface
only directly as the diameter of the
rivets, but the shearing strength as the
square of the diameter. - We should
therefore increase the pitch in proportion
to the square of the diameter, assuming
of course that we are dealing with a
joint well preportioned in the first in-
stance, in which the plates between the
holes should have a margin of tensile
strength over the shearing strength of
the rivets, since the plates are liable to
become reduced in strength by punching
and wasting, whereas the portion of the
rivet between heads being protected
does not become so much reduced.
When the joint is not so proportioned,
the less are we justified in still further
giving a preponderance of strength to
the rivet already too large. The great-
er the pitch of rivets the more is the
strain concentrated at the sides of the
holes, and consequently the greater is
the tendency of the plate to be broken
piecemeal and the breaking strength to
be thereby reduced. Hence increasing
the size of the rivets and attempting to
maintain the efficiency of the joint is
tantamount to increasing the brittleness
of the plate, and by injudiciously pro-
portioning a joint we may to some
extent at least neutralize the advantages
expected to be gained by annealing and
using a ductile material.
One very important point should not
be lost sight of in proportioning a joint,
and this is that it is far more difficult to
make a good repair job with large rivets
than with small ones, especially in inac-
cessible situations, and where the pitch
is increased to maintain the section be-
tween rivet holes when using large
rivets, the difficulty of making tight re-
pairs is still further increased.
Perfect tightness in a joint without
theoretical correctness of proportion is
of far more importance than correct pro-
portions which may fail to secure perfect
tightness. One boiler-maker may have
appliances which will enable his men to
make perfectly tight and sound work
with rivets of unusually large diameter
and pitch, and with which another maker
would fail to make satisfactory work.
The cases of boilers that have given way,
and of expensive repairs that have been
required through the rivets being too
small, are very rare in comparison with
the disasters that have occurred, and the
expenses that have been incurred^
through wasting of plates in consequence
of leaky joints. No doubt it is advisable
to keep up the ultimate breaking strength
of the joint by increasing the diameter
and pitch of rivet, but it is absurd to do
it to such a degree as to risk making the
plate weaker in the solid than in the
joint, which it will inevitably become in
time should the joint leak. If the wast-
ing of steel plates occasioned by leakage
took place only at the same rate as that
of iron plates, the reduction in thickness
with the former would render them less
durable. But there is reason to believe
that the wasting will be more rapid with
steel in certain situations, hence the im-
portance we attach to having perfectly
STKTJCTUKES IN AN EARTHQUAKE COUNTRY.
271
tight joints, lest the material should be
blamed, instead of the design and work-
manship, in the case of a boiler wearing
out rapidly. The crippling strength of
a ductile steel plate in front of the rivet
may be considerably increased by in-
creasing the lap or distance between the
edge of the plate and center of rivets.
With lap joints the practical objection
to this is that beyond a certain limit,
usually taken at one and a half times
the diameter of rivet, the difficulty of
making a joint tight by caulking or
"fullering" increases with the amount
of lap.
But in butt joints this objection is
got over by increasing the lap of the
plates only whilst retaining the usual
amount of lap between the rivets and
the caulking edges of the strips or welts.
In double-riveted lap joints a consider-
able advantage in strength will be gained
by increasing the distance between the
lines of rivets in steel plates beyond the
usual practice for iron plates, especially
STRUCTURES IN AN EARTHQUAKE COUNTRY.
By JOHN PERRY and W. E. AYRTON, Professors in the Imperial College of Engineering, Tokio, Japan.
From "The Architect."
When working at our paper on " A
Neglected Principle that may be Em-
ployed in Earthquake Measurements,"
read before the Asiatic Society of Japan,
May 23, 1877, we were led to consider
how the effect produced by an earth-
quake on a structure is influenced by the
time of vibration of the structure.
It follows from that principle that if a
number of quickly vibrating bodies form
part of the same structure, they all
vibrate in much the same way; that is,
the periods of their swings are all ap-
proximately equal to one another and
equal to the periods of the earthquake;
and although they differ in the amount
of their motions these amounts and their
differences are all exceedingly small;
whereas if one or more of the parts of
the structure are only capable of vibrat-
ing slowly, the periods of vibration of
the different parts vary very much, the
amounts of the motions are all compara-
tively great, and their differences are all
relatively considerable. If, however,
there is a sufficiently great viscous re-
sistance to motion of such slowly vibrat-
ing parts, these parts will be found
during an earthquake to behave much as
if their natural periods of vibration were
quick. Supposing the foundation of a
structure to vibrate with the earth which
encloses it, we see that a slowly vibrat-
ing structure which is fastened to these
foundations is during an earthquake sub-
jected to stresses which may be exces-
sively great and of a very complicated
kind, whereas a quickly vibrating struc-
ture is subjected to stresses which may
be said to be determinate, and which are
comparatively small. It is not here
necessary to consider whether, as all the
motions of a quickly vibrating body
must be small, such a structure will be
more comfortable to live in, because it is
doubtful whether the annoyance pro-
duced by rapidity of shock would not
more than counterbalance the annoyance
of great but smooth motions. It is only
safety we are here considering, and in
this respect there can be no doubt of the
superiority of rigid structures, or of
structures having a sufficiently great
viscous resistance to motion. We have
made some calculations of the times of
vibration of ordinary structures, such as
well-built houses of stone and brick,
chimneys, lighthouses, &c, and from
these we see that the periods are all
much less than what we judge from our
experience is the ordinary period of vi-
bration of earthquakes in Japan. Even
two-storied houses built of wood if
framed in the best way have quick times of
vibration; such structures are, therefore,
it seems to us, well capable of resisting
the ordinary Japanese earthquake shock.
As, however, we have not yet experi-
enced the effects of a destructive earth-
quake, and as we presume that one of
272
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the most important ways in which it may
differ from ordinary earthquakes is in the
suddenness of motion, or change of mo-
tion, it cannot be said that any ordinary
structure has a quicker period of vibra-
tion than a destructive earthquake; con-
sequently, if it be granted that stability
depends on the structure having a quicker
period of vibration than that of the
earthquake, the stability of a building
will be only relative; we can, of course,
be sure that by making the walls of a
building thicker and its height less that
we add to its safety, but however far we
may go in this direction we cannot be
certain but that after all the earthquake
period may be less than that of our build-
ing.
We must, therefore, content ourselves
with saying that a slowly vibrating
structure will probably get broken in its
connections with the foundations if these
be rigidly fixed to the ground, conse-
quently (and we here oppose the prac-
tice of many architects and engineers)
putting a heavy top to a lighthouse, the
chimney of a factory, or other high
building, must certainly take from its
stability. And although the times of vi-
brations of ordinary brick and stone
houses are very short, still in view of the
possible great suddenness of a destruc-
tive earthqaake we should advise that all
buildings be kept as low and made as
rigid as possible.
The argument used by engineers to
support the practice above referred to of
placing a heavy top on a chimney as-
sumes that the shock is an impact, and,
consequently, that a definite quantity of
momentum is given to the structure, but
it must be quite evident that it is the
relative velocity of the base of the struc-
ture with regard to the other parts
which is the fixed quantity, and, there-
fore, that the more massive the structure
the more momentum enters it through
the base.
There is no easy way of judging what
are the forces which cause an ordinary
Japanese house to return to the perpen-
dicular position after it has received a
push or blow, and so we cannot calculate
its natural time of vibration; but it is
well known that it vibrates very slowly,
an ordinary Japanese two-storied house
with the usual heavy roof taking per-
haps four seconds to make a complete
vibration. Th<e restoring forces are due
merely to stiffness of the joints, there
being no rigid connection with the
ground since the vertical posts of the
house are all supported on detached
stones, and there are also no diagonal
stays in the building. Such a structure
is therefore capable of being displaced
very far from its position of equilibrium
without fracture occurring, and as its
time of vibration is very long, it has a
very great amplitude of swing during
most ordinary earthquakes ; that this
amplitude is not even greater is most
probably due to the fact that there is a
sort of viscous resistance to motion at all
its joints. Such a viscous resistance
must greatly diminish the motion, and
will be especially useful in an earthquake
consisting of regular vibrations, but the
most severe test of such a structure con-
sists in an earthquake shock which
begins with a sharp impulse, or which
has a very irregular motion. The slowly
vibrating structure would register the
shock in a longer period of time than
that in which the blow was delivered,
but it would probably have an exceeding-
ly great first swing from its position of
rest.
We think that the important elements
of safety in ordinary Japanese structures
is this viscous resistance which they op-
pose to motion, and which is mainly due
to the great multiplicity of joints (all of
which are compelled to move) and to the
absence of diagonal pieces; for we de-
duced from the principle in our original
paper, that if the restoring forces are
weak there ought to be a great viscojis
resistance to motion if we wish the
strains of the structure to be small.
But it must be remembered that this
safety is only gained by a very great ex-
penditure of timber, so that although
such slowly vibrating structures as many
of the temples may be regarded as ex-
ceedingly safe during earthquakes, it
must not be concluded that all heavily-
roofed houses are secure.
The amount of momentum which has
to be transmitted through the founda-
tions of a building to the superstructure
depends on the nature of the earthquake
— that is, its suddenness and the amount
of earth motion, as well as on the mass
of the building, while the velocity of the
foundations, if these are rigidly con-
STRUCTURES IN AN EARTHQUAKE COUNTRY.
273
nected with the earth, is independent of
the mass of the building, an important
fact to which we have already drawn
attention. The earthquake energy gets
destroyed by the interior portions of the
earth as well as the mountains and
buildings at its surface, not having ex-
ceedingly small periodic times of vibra-
tion, in consequence of which interfer-
ence takes place, at every surface of con-
tact of the different portions. Of course,
however, any one particular building
will destroy only a very small portion of
the whole energy of the earthquake vi-
bration, so that its mass cannot in any
preceptible way affect the motions of its
foundations.
In the same way as we have shown
that the more quickly a house is capable
of vibrating the less is its motion relative
to the foundation, we might arrive at
the result that the smaller the natural
period of vibration of the several por-
tions of a body subjected to shocks the
less internal friction must there be; and
this conclusion is consistent with the
well-known fact that there is more inter-
nal friction in non-homogeneous bodies,
or rather, we should say, in bodies
which, being non-homogeneous, have
some of their materials only capable of
very slow natural vibrations compared
with the remainder.
We have no doubt but that with any
given material whatever there is a best
method of constructing buildings in an
earthquake country. Thus with small
stones set in bad mortar, or in no mortar,
as in the buildings destroyed by the
Neapolitan earthquake of 1857, the mo-
mentum which must pass through any
level joint depends (I) on the short time
t during which the foundations are ac-
quiring a great velocity v; (2) on the
mass of the building M above the joint;
and (3) on the natural time of vibration
of the portion of the structure between
the given joint and the foundations. If
this time of vibration is very short then
the momentum Mo must be transmitted
by the joint in the short time t — that is,
the joint must transmit the great force
— ; whereas if the time of vibration of
%
the building below the joint is considera-
ble, the time of transmission of moment-
um is increased in a calculable way, say
to the time nt, and hence the force traus-
Vol. XIX.— No. 3—18
mitted by the joint becomes reduced to
Mo
— . It is for this reason that if we wish
nt
to drive in a nail without hurting the
head with the hammer a block of wood
is used as a cushion, the wood being of
service because having an appreciable
time of vibration it causes the duration
of the impact to be lengthened, and so
diminishes the force acting at any mo-
ment. In the same way the lower parts
of a structure having appreciable times
of vibration cause the earthquake shock
to be altered in character, to be length-
ened in time, and, therefore, diminished
in intensity before it reaches the upper
parts. Hence it is obvious that if small
stones or bricks set in bad common mor-
tar are our building materials it would
be better to choose, for the site, a quak-
ing bog, which was capable of support-
ing the weight of the building, rather
than to build the house direct from a
rocky foundation, or if the ground is
firm there ought to be placed underneath
the house a foundation of yielding tim-
ber, or some other method should be
sought for by means of which the time
of transmissions of momentum through
the joints may be increased.
Thus there is a best time of vibration
of the part of a structure below a joint,
which depends on the strength of the
joint; and if the basement has a time of
vibration different from this, then, we
should advise that the building be kept
low. For example, it is desirable that
houses with ordinary wall thicknesses
built of bricks set in common mortar
should not be more than one, or at the
very most two stories high if there is a
piled or concrete foundation; but if good
cement be employed instead of bad mor-
tar, then a height of two or three stories
may be employed probably with com-
parative safety.
Again, the horizontal vibration of the
ground is given up to a stone or brick
building mainly by shearing stress com-
municated from course to course, a kind
of stress which mortar is very unsuitable
to transmit. Hence, a stone or brick
building -subjected to horizontal shocks
ought certainly to be built with cement,
and not with ordinary mortar. In fact,
in every part it ought to be capable of
resisting pulling as well as crushing
stresses.
274
VAN NOSTRAND's ENGINEERING MAGAZINE.
Every joint is a weak place, and it is
evident that if, by increasing the size of
the building, we diminish the area of
joints we shall be increasing the stability.
Now, in large masonry structures larger
stones are as a rule employed, and the
joints are made of less area. In this re-
spect, then, may we say that large ma-
sonry structures built with common mor-
tar are usually more stable than smaller
ones.
It is quite evident that, as concrete can
be obtained which will resist as great a
tensile stress as ordinary brick itself, we
shall derive great benefit from making
all horizontal sections of a structure,
which is composed of bricks set in good
cement, as great as possible — that is, we
shall find that the most suitable struc-
ture, if of brick or stone, for an earth-
quake country, should be composed of
large stones set in good cement, with
walls as thick as possible near the base,
the thickness of wall at every place be-
ing roughly proportional to the mass of
the building above that place.
As, however, the resistance to tension
of timber is very much superior to that
of cement or bricks, and as the mass of
a timber building is small, a timber
building with sufficiently strong joints
must be very much superior to any
structure of brick or masonry. And, for
the same reason, a building of wrought
iron might be made stronger still, and one
of steel strongest of all.
Ordinary timber houses ought not to
be too rigidly fastened to the earth; if
the joints of the structure are made,
however, very strong, and especially if
wrought iron is used as well as wood,
and if there is diagonal bracing, then the
connections with the ground may be made
more rigid. The stiffnesses of struc-
tures vary so much that we cannot give
more definite rules than those contained
in this short article, but it is obvious that
our principle of relative vibrations may
be easily applied to find the best arrange-
ment in a structure for any given mate-
rial, and with any given foundation.
STEEL SHIPS.
From " The Nautical Magazine.'
We have reluctantly felt compelled
to place the heading " Steel Ships" be-
fore this paper, but would desire to
repeat our former observation that the
new metal is not steel at all, but merely
ingot iron. Our readers will pardon
this reiteration when they are told that
some great authorities on the subject
have been so far led away by the name
as to adduce experience of the wear of
some decided steel ships which have
been afloat for years, as proof of the
reliableness of the new metal of an
essentially different character, although
bearing the same name. So far as its
composition goes the new metal is rather
an exceptionally pure iron than a steel, and
for aught we know at present, may ulti-
mately develope qualities the reverse of
those of ordinary steel. The cautions
recommended in using it, and the careful
testing of each plate, are rendered neces-
sary by the fact that in the present state
of the new processes of manufacture we
cannot without test be absolutely certain
that the metal obtained is the real bona
fide ingot iron or mild steel. Mr. Wims-
hurst suggests that in consequence of
the great ductility of the new metal, the
ordinary system of riveting may be
found insufficient, but wisely does not
lay down any rules to be followed, and
concludes with the excellent practical
suggestion that in all cases of passenger
ships built of mild steel "frequent easily
made surveys should be held during the
first year," which surveys " need not be
of such a character as to interfere in the
least with the engagements of the vessel,
hut they will afford the Board a prompt
and effective means of checking any evil
which may be found to arise."
We have, in our present paper, to
notice a lengthy and important commun-
STEEL SHIPS.
275
ication made to the Institution of Naval
Architects, by the Chief Surveyor to
Lloyd's Registry, on the subject, and
giving in great detail the result of a
•eries of experiments instituted by the
Committee of Lloyd's Register. Mr.
Martell begins his paper by some re-
marks upon the prospects of the general
adoption of the new material, and ap-
pears to regard the question as practi-
cally settled. He says, "The time has
now come when it is said by many
others, besides the manufacturers, that
steel can be used with as much confi-
dence as iron, and it is held that whilst
the properties of mild steel are in every
respect superior to iron, the cost, having
regard to the reduced weight required,
will warrant the shipowner, from a com-
mercial point of view, in adopting the
lighter and stronger material." We
have also the important fact that during
the last twelve months the Committee
of Lloyd's have had before them pro-
posals for 5,000 tons of sailing ships, and
18,000 tons of steamers, to be built of
mild steel.
We are glad to hear that, so far as
they have gone, Lloyd's fully agree with
the Admiralty as to the practical value
of mild steel. As regards its working
qualities Mr. Martell produced a speci-
men "shingled " from cuttings of plates
which were in use, and which had stood
a tensile strain of 26 tons per square
inch. Experiment proved that its be-
haviour in the fire and under the ham-
mer was just that of ordinary iron: in
fact, the welds were cleaner and more
perfect. The first series of experiments
were made upon the strength of riveted
joints, the results being, briefly, that iron
plates double-chain riveted with iron
rivets, the holes being punched, devel-
oped a mean tensile strength of 17.9 tons
per square inch. Steel plates connected
with iron rivets gave out by shearing of
the rivets at a strain 16.7 tons per square
inch of rivet area, the strain upon the
plate only reaching 15.3 per square inch.
Steel plates connected with steel rivets
developed a mean strength of 22.5 tons
per square inch. The result of these
experiments, if borne out by similar
results with more extended experience,
will be to prove, that in using iron rivets
with steel plates we must have a larger
proportion of rivet area to the plate area
between the holes for double riveting, or
the plates must be treble riveted unless
it be found that steel rivets can be used
with good results, in which case the ordi-
nary scale of riveting will be sufficient.
As regards the practical use of steel
rivets, in addition to the practical experi-
ence at Glasgow to which we adverted
in our former article, Mr. Martell states
that they have been recently satisfactor-
ily used in two steel vessels, built by
Messrs. Laird, of Birkenhead. Special
care must however be taken to make
sure that the rivets are really mild steel,
and even then it is desirable that they
be uniformly heated, and not at too high
a temperature. As an illustration of
this, a case is adduced where some build-
ers tried steel rivets, and found that
after some landing edges of outside plat-
ing had been riveted, many rivets were
broken mostly between the plates; and
in this case iron rivets were ultimately
used throughout the vessel. Subsequent
experience has shown that mild steel
rivets can be safely used by ordinary
riveters, and what is more, with the or-
dinary rivet boys; and we must conclude,
therefore, that the rivets which failed
were not made of true mild steel.
A second series of experiments were
undertaken with a view to ascertaining
the relative effect of punching upon mild
steel and upon iron plates. The results
are thus summarized:
" 1. That steel plates very thin suffer
less from punching than iron.
" 2. That the difference in loss of
strength by punching on steel and iron
does not appear sufficiently great to re-
quire special precautions to be taken for
steel more than for iron in plates up to
T8g- inch in thickness.
"3. That in plates above eight-six-
teenths in thickness, the loss of strength
of iron plates by punching ranged from
twenty to twenty-three per cent:, while
in steel plates of the same thicknes it
ranged from twenty two to thirty-three
per cent, of the original strength of the
plate between the rivet holes. An occa-
sional plate, both of iron and steel,
showed a smaller loss than the mini-
mum stated, but they were exceptional
cases.
" 4. That by annealing after punching,
the whole of the lost strength was re-
stored, and in some instances greater
276
VAN NOSTRAND'S ENGINEERING MAGAZINE.
relative strength was obtained than ex-
isted in the original plates.
" 5. That the steel was injured only a
small distance around the punched holes,
and that by riming with a larger drill
than the punch, from y1^- inch to J inch
around the holes, the injured part was
removed, and no loss of strength was
then observable, any more than if the
hole had been drilled.
" 6. That in drilled plates, no appre-
ciable loss of tensile strength was ob-
served."
Mr. Martell then, at some length, con-
siders the respective disadvantages of
riming the holes or annealing the
plates. He also shows that, even after
allowing the twenty per cent, less scant-
ling for steel, and supposing a further
loss of thirty per cent, by punching the
plates, as compared with the twenty per
cent, loss due to punching in ordinary
iron, the advantage is still with the steel.
A better solution of the difficulty than
annealing will probably be found in the
use of some kind of punch which will
distress the iron less than the common
one does. Some of the experiments
proved that the loss due to punching,
when the patent spiral punch was used,
was 2£ tons per square inch less than
with the common punch.
The second part of Mr. Martell's paper
Is devoted to the question of the relative
cost of vessels built of mild steel and of
iron, taking into the question the reduced
weight of hull and consequent larger
carrying capacity of the former. In the
first place, he disposes of the objection
that mild steel is of so much greater
specific gravity than iron as to detract
considerably from the advantage of the
smaller scantlings offered by Lloyd's. It
has been said that the difference was as
much as 4 per cent., data furnished by
Messrs. John Brown & Co., the well-
known Sheffield firm, fix it at 2.66 per
cent., and Mr. Bessemer states it to be
still less. Mr. Martell goes into details
as to the first cost, and subsequent yearly
profit of a steamer 2,300 tons gross, sup-
posed to be built for the Indian trade,
and makes out that with a cargo of coals
out and measurement goods home, the
additional freight of the steel ship would
just pay the percentage on her additional
cost, but with a dead weight cargo out
and home there would be a profit on the
voyage of 6f per cent, in the steel ship
as against 5^ on the iron ship. With
sailing ships the gain is not so clear, al-
though, from the fact that a sailing ves-
sel of 1,700 tons is now being built of
the new material, it would appear that
at least one large shipowner believes
that even in the case of sailing vessels
the additional freight would pay interest
on the additional cost. Obviously a
saving of weight in the structure is of
very much more importance in a steamer
than in a sailing ship; in the former, the
machinery and coals absorb so much of
the carrying capacity that the addition
of a few tons to the freight gives a larger
percentage on the total freight.
As regards the durability of the new
material, Mr. Martell can tell us little
more than has been known for some time
past. We agree with him that the fact
that the Admiralty are going to build
some small torpedo vessels of brass or
bronze instead of steel is nothing to the
point. It has been found that some of
the thin steel torpedo vessels have in a
very short time become very much pit-
ted; it must be remembered, however,
that they are only -fa inch thick, and
an amount of deterioration hardly
noticeable in another vessel would be
serious in them. Less to the point are
the other remarks as to the durability of
some vessels built of steel some years
ago, and which have worn well. It can-
not be too much insisted upon that these
vessels were built of bona fide steel,
whereas the new metal, mild steel, in
some of its properties, is much more an-
alogous to wrought iron than to steel.
Especially is such the case in the most
important feature, as regards decay.
The chemical analysis of mild steel shows
a larger percentage of pure metallic iron
than is found in any commercial wrought
iron.
Probably with the increased demand
for mild ship steel the cost of production
may, in a few years, be so diminished
that it may successfully compete with
wrought iron for all kinds of ships. At
present it will probably be used in many
steamers, more especially in vessels de-
signed for speed, in which, as compared
with ordinary steamers, every ton of in-
creased freight is of as much greater im~
portance, as in the comparison between
ordinary steamers and sailing ships.
THE BRAKE AS A DYNAMOMETER.
277
THE BRAKE AS A DYNAMOMETER.
From "The Engineer."
The friction brake is so generally re-
garded as an essentially accurate instru
ment for ascertaining the power develop-
ed by a steam engine or water wheel,
that it requires some courage even to
suggest that it is perhaps not quite such
an instrument of precision, after all, as
some persons would have us think. The
friction brake is more used by builders
of portable engines than by anyone else.
There is scarcely a respectable agricul-
tural engineering works in the kingdom
in which the friction brake is not regu-
larly and frequently employed. But the
great majority of mechanical engineers
engaged in the construction of marine
engines, locomotives, or stationary en-
gines of large power, know nothing
practically about it. It is, therefore, to
the experience of agricultural engineers
that we must turn for such information
as may enable us to form an estimate of
the true value of the friction brake as a
power-testing machine ; the remainder
of the engineering community can, as we
have.said, tell us nothing whatever that
is not theoretical about it. Now it so
happens that many agricultural engi-
neers say that they have found by
experience that the friction brake is by
no means so precise an instrument as
theory would have us believe. Indeed,
unless these gentlemen are wholly mis-
taken, the brake may, theory to the
contrary notwithstanding, prove very
deceptive. Everything, it it is said,
depends on the condition of the brake.
If that is perfect, then a high duty can
be got from an engine; if it is imperfect,
then the performance of the engine will
be bad. To explain our meaning, it is
necessary to go back to the days when
prizes were given by the Royal Agricul-
tural Society for portable engines. The
competing engines were made and tested
daily for months before they came to
the public trial. Now, it was well
known to those who superintended the
daily runs made with a racing portable
engine, that whereas on some occasions
a run of, say, four hours could be obtain-
ed with 14 lbs. of coal per brake horse-
power, on other days the run would not
exceed three and a-half or three and
three-quarter hours, and there was no
possible explanation of the circumstance
save that the brake did not work smooth-
ly. Carrying this experience into prac-
tice, engineers always did their best
when competing publicly, to get a brake
which had been worked until it was in
perfect order ; and some of the most
eminent authorities on racing portable
engines maintained that the difference
between a brake in what is known as a
good condition and one in bad condition
may be such as to affect the length of a
run by from five to ten minutes.
Such conclusions and experiences as
we have just noticed are totally opposed
to the received theory of the friction
brake; yet it is impossible to ignore
them, and it may be found that the ap-
parent incompatibility may be reconciled
by adding something to the theory which
is in no way opposed to physical truth.
The friction brake or dynamometer con-
sists of a smooth pulley some 5 feet in
diameter, round which run twTo hoops of
iron lined with blocks of elm, beech, or
willow. The hoops can be tightened by
a hand screw, and when so tightened
would, if permitted, revolve with the
pulley. To prevent this they are fitted
with a simple lever arragement by which
the straps are slackened if they move
through a short distance with the pulley,
and at one side of the ring of wood
blocks is suspended a weight, calculated
according to the power required. This
weight is kept in suspension the whole
time that the pulley is running, its
weight being just sufficient to equal the
frictional resistance of the blocks on the
rim of the pulley. This being so, it is
assumed that the resistance offered to
revolution by the apparatus will exactly
equal the power that would be required
to wind the weight on the brake out of a
pit, say, of great depth. Let the dis-
tance from the point at which the break
load is suspended to the center of the
brake pulley shaft be such that, using it
as a radius, a circle 33 feet in circumfer-
ence would be described, then for every
1 lb. of brake load and one revolution of
278
VAN NOSTRAND S ENGINEERING MAGAZINE.
the brake pulley 33 foot-pounds of work
will be done. Let the revolutions of the
brake be 100 per minute, then every
pound of brake load represents 33 X 100
X 1 = 3300, and every 10 lbs. of brake
load becomes 33 X 100 X 10 = 33,000
foot-pounds per minute=one horse
power. It will be seen that the appar-
ently absolute measure of the work done
is the load on the brake and the surface
speed. The maximum resistance the en-
•gine can have to overcome is measured
by the weight, because if the hand screw
is tightened the weight will rise, and
would be carried round with the wheel
but for the levers before referred to;
while, on the other hand, if the straps
were released, the weight would fall a
little until the straps automatically
tightened it again. According to theory,
again, the condition of the brake has no-
thing to do with the matter. If the sur-
faces of the pulley and the wood blocks
are rough, then the hoops must be left a
little slack. If, on the other hand, the
surfaces are beautifully smooth and well
oiled, then the hoop must be tighter, but
in either case the resistance offered to the
engine is precisely the same, and is
measured by the weight which hangs
balanced in mid-air while the engine is
running. There can be no doubt that
this reasoning is extremely plausible,
and would be quite convincing if it only
covered the whole of the ground to be
traversed. But let us ask ourselves
what becomes of the power developed
by the engine ? No useful work is done;
the weight is not lifted, and the only re-
ply is that the power is transformed into
heat; that is to say, the engine heats up
the brake pulley and its connections,
and it also heats up the water or oil used
for lubrication. This heat is dissipated
by conduction and radiation. It amounts
to 42.75 thermal units per horse-power
per minute.
An engine working up to 20-horse
power develops as much heat in the
brake as would rise from 62° to the boil-
ing point 34'2 lbs., or say 34 gallons of
water per hour. All this is quite intelli-
gible, and a little examination will show
that the engine, instead of lifting a
weight, works against friction, and it is
assumed that the weight is a precise
measure of the amount of friction, or, to
speak more accurately, of the quantity
of heat which will be transferred per
hour from the engine to the brake, and
thence to the air and the lubricants. On
this point the whole theory of the fric-
tion brake really turns, and unless it can
be proved that a given weight resting on
a polished surface running at a given
speed beneath it can produce an amount
of heating which is invariable under all
circumstances for the same conditions,
then the theory of the brake must be re-
garded as incomplete. Hitherto almost
all writers on this subject entirely neg-
lect the consideration of the heat im-
parted to the brake. They allude to it,
indeed, but only incidentally, and they
say nothing whatever concerning the re-
lation between the brake load and the
heat developed. They content them-
selves with considering the duty done
by the engine to be precisely similar to
the work of lifting a weight, whereas
they are totally dissimilar, and if it could
be shown that under certain conditions
a given brake load would convert great-
er or lesser quantities of engine power
into heat, then the idea that the friction
brake is thoroughly reliable dynamo-
meter would have to be abandoned. It
is well known to all who have had ex-
perience that friction brakes will run
sometimes hot and sometimes cool, and,
according to those whose experience
constitutes the best authorities, that the
cooler a brake runs the smaller is the
power required to work it. If this be
true, then it is evident that the usually
received ideas concerning the merits of
the brake as a dynamometer must under-
go some modification.
It will be understood that we have ad-
vanced nothing concerning the friction
brake which will not be confirmed by
many engineers who have used it much.
It is difficult to reject as valueless opinions
which we have heard expressed over and
over again for years, and the accuracy
of which is suggested by our own expe-
rience. All that we have now endeav-
ored to do is to show how it may be pos-
sible to reconcile theory and practice. It
is certainly possible to conceive that
under all. possible circumstances the
coefficient of friction need not bear an
invariable relation to each other. Let
us suppose that the coefficient of friction
of well lubricated wood blocks is -g^, and
that the weight to be supported is 100 lbi.
REPORTS OF ENGINEERING SOCIETIES.
279
then the blocks must be applied to the
wheel with a force of 5000 lbs., and the
heat developed on the brake per minute
will be 427.5 units. Now it is absolutely
certain that the conditions of speed, load
&c, being constant, the rate of conver-
sion of power into heat must also be con-
stant. In other words, is there an
invariable relation between frictional
resistance and heat developed? That
an approximate relation does exist we do
not for a moment question, but that any-
thing like an invariable correspondence
can be proved to exist, is open to ques-
tion. Those who have the means of
settling the point by actual experiment
should do so. The friction dynamome-
ter is no doubt a substantially accurate
machine ; but if a legal difficulty arose
to-morrow about the power of an engine,
a jury would soon have reason to believe
that even under the best arrangements
the friction brake may be as much as
perhaps 10 per cent, wrong in its indi-
cations.
REPORTS OF ENGINEERING SOCIETIES.
The Institution op Mechanical Engineers,
held meetings in Paris in June. The fol-
lowing papers were read:
Further Researches on the " Flow of Solids";
by M. Henri Tresca, President of the Societe
des Ingenieurs Civils.
On the Hydraulic Machinery at Toulon
Dockyard; by M. Marc Berrier Fontaine,
Ingenieur de la Marine, Toulon.
On Mechanical Traction upon Tramways;
by M. Analole Mallet, of Paris.
On the Greindl and other Rotary Pumps; by
M. L. Poillon, of Paris.
On the Vapart Disintegrator; by M. Prosper
Closson, of Paris.
On Compound Engines fitted with Correy's
Variable Expansion Gear; by Mr. Thomas
Powell, of Rouen.
On the Effect of Brakes upon Railway
Trains; by Captain Douglas Galton, C.B.,
F.R.S., of London.
On Lighting by means of Electricity; by M.
Hippolyte Fontaine, of Paris.
IRON AND STEEL N0TES-
Analyses of Russian Iron. — Mr. Sergius
Kern has written from St. Petersburg
commenting upon the remarks of Mr. E.
Riley, that he was astonished that most of the
steels, the analyses of which appeared in Mr.
Kern's late paper, contained only traces of Ph.
and S. Mr. Riley also complained that the
percentage of Mn. was too low in the analyses,
and added that perhaps Mr. Kern used inferior
methods for the detection of Ph. S. and Mn.
The following are the answers of Mr. Kern:
"(l) The steels in question were prepared from
Oural pig-irons; most of them, indeed, contain
only traces, or nil, of Ph. and S. Charcoal is
used as fuel. (2) The methods I use belong to
Eggertz, and may be found in his classical
manual ' Om Kemisk profning af Jern, Jern-
malmer och Braenn mateiialier.' Using the
methods of the well-known Professor V.
Eggertz, I cannot understand why I should
prefer other methods. (3) As for the low per-
centage of Mn., I will only mention that I can-
not understand what Mr. Riley wishes, as it is
not my fault that the Russian steels contain
such a low percentage of Mn."
At the Philadelphia Exhibition, it will be re-
membered, an International Committee,
consisting of commissioners who were over re-
porting for the different countries, had a dis-
cussion on the classification of iron and steel,
and proposed new definitions. Among those
on the committee were Mr. I. Lowthian Bell,
M.P., F.R.S.. and Dr. Reuleanx, of Berlin.
The German Ironmasters' Association has, ac-
cording to the Iron and Goal Irades Journal,
just had this classification under discussion,
and resolved : — (1) that a general classification
of iron and steel is neither necessary nor use-
ful ; (3) that the tests now customary for test-
ing iron and steel goods — hammering, bending,
and loading for rails, bending for axles, pulling
for sheets, &c. — are sufficient ; (3) a specifica-
tion of limits of value of the properties of iron
and steel goods in reference to their uses is de-
sirable ; (4) that a further prosecution of the
experiments hitherto conducted by the associa-
tion, with common commercial irons, is there-
fore desirable, in view to an eventual special
classification of railway material ; (5) that State
testing be placed under the control of a com-
mission, consisting on the one part of delegates
chosen by consumers and producers alike, and,
on the other, of approved men of science ; (6)
quantities of metal in railway contracts to be
determined by ironmasters conjointly with the
railway engineer ; (7) that the proposal made
by Dr. Reuleaux, to draw up a table of proper-
ties, and stamp goods with a mark correspond-
ing to a designation in the table, is impractica-
ble.
Siemens-Martin Metal Ruled to be Steel.
— Secretary Sherman has sent a letter to
the Collector of Customs at Boston, Massachu-
setts, in which the vexed point of how Sie-
mens-Martin metal is to be taxed, is disposed of.
The text is as follows : — "The Department, by
decision of December 1st, 1874 (Synopsis 2025),
held that metal produced by what is known as
the ' Martin-Siemens process ' should be
charged with the duty imposed upon steel,
such process being considered a steel-making
process, designed only to produce an article
having the 'quality of steel.' Subsequently,
upon further consideration, and upon addi-
tional facts at that time submitted, the Depart-
ment, by letter of July 14th, 1876 (Synopsis
2891), expressed its conviction that both iron
and steel are produced by the Martin-Siemens
process, and that, consequently, the fact of
manufacture by that process was not of itself
280
VAN nostrand's engineering magazine.
conclusive ground for classifying the product
as steel; but that the question whether any
particular importation was iron or steel was
one of fact to be determined by the appraisers.
It has recently been ascertained that a want of
uniformity has prevailed at the ports of New
York and Boston in the classification, since the
later decision, of importations of metal pro-
duced by the Martin-Siemens process ; metal
of that character, and similar in every respect,
having been, without exception, classified at
the first-named port as steel and at the latter as
iron. In view of these facts, the Department
has again had the matter under consideration,
and has submitted the question of the character
of this metal to experts, metallurgists, and the
most prominent manufacturers of, and dealers
in, iron and steel in the United States. A
careful consideration of the reports and opin-
ions of these persons satisfies the Department
that the Martin-Siemens process was intended
to be, and is essentially, a steel-making pro-
cess, and that the product of such process must
consequently be steel or an article possessing
the general characteristics of steel, and used
for the purposes to which steel is applied In
confirmation of the correctness of this view, it
may be stated that the classification at the port
of New York of the metal in question as steel
has been accepted without dissent by importers
of that city, and that protest against payment
of duty exacted on such classification has in no
case been made. After a full examination and
consideration of all the facts and information
bearing upon the question at issue, the Depart-
ment is of opinion that the classification as
iron, of metal produced by the MartiE- Siemens
process, is erroneous, and that all metal pro-
duced by that process should be hereafter
classified as steel, and assessed with duty ac-
cordingly. The decision of the Department of
the 14th July, 1876, hereinbefore referred to, is
therefore revoked, and decision 2025 will be re-
garded as in full force. "
RAILWAY NOTES.
The St. Gothard Railway Co. finds some
difficulty in obtaining the money neces-
sary to complete its work. According to the
original understanding under which the under-
taking was begun, Italy was to have con-
tributed $9,000,000; Switzerland, $4,000,000;
the Nortfi German Confederation, $2,000,000;
the Grand Duchy of Baden, $ 600,000, and the
other German States the additional cost. Now
Switzerland is asked to contribute as a nation,
instead of by States, $ 1,300,000, on condition
that the Northern & Central Railway Co.
gives $300,000 more, which, it is estimated,
will complete the road. Whether these sub-
sidies are in addition to those originally agreed
upon does not appear in the dispatch. The
road will connect Luzerne and Milan by rail,
and the division of cost between the nations is
supposed to represent the proportion of bene-
fits to be derived by each from its construction.
It now requires fifteen fifteen hours to cross
the Alps by the St. Gothard pass in the dili-
gence from Fluelan to Bellinzona,
In discussing the recent half-yearly report of
the Great Indian Peninsular Railway,.
Colonel Jas. Holland said: — "In the corre-
sponding half of last year the proportion of
English to native fuel used was 84 per cent, of
English to 16 per cent, of native coal. Last
half-year the proportion was 68 per cent, of
English to 32 percent, of native, so that we
are coming to use native coal more considera-
bly. I only wish I could say that the native
fuel was as good as the English. It is, how-
ever, excepting that from Bengal, very in-
ferior, but that, though good, is as dear as coal
from England. It would shock any one ac-
customed to English coal to see with what rub-
bish from Wararo we work our line. It pro-
duces a vast quantity of sparks, and a consid-
erable portion of the compensation paid for
damage to goods has been owing to burning
inferior coal. We find with the new and
powerful engines now day by day coming upon
the line that they puff and blow less ; the
sparks are consequently fewer. We may now
be said to be using about one-third native coal ;
last year we used about 10,000 tons of native,
this half-year we shall probably use about
30,000 tons."
The Belgian Grand Central Railway Com-
pany, in their annual report for 1877, pub-
lishes some statistical tables showing, for the
period from 1865 to the end of 1876, the num-
ber of rails removed from the track, of those
deteriorated but not removed from the track,
removed and deteriorated, the number of re-
maining in the track uninjured, both of iron
and steel. From these tables it appears that
all the iron rails used before 1873 are of bad
quality, except those laid in 1867, 1869, and
1870 ; these latter are hammered rails. Of the
rails laid since 1873, the quantity removed is
insignificant ; this is because for the past few
years the management of the Grand Central
makes sure of the quality of the rails, and pur-
chases only of works which offer sufficient
guarantees under this head. The quantity of
rails in the track on the last of January, 1878,
was 37,000 tons of iron, and 3385 tons of steel
rails, and to maintain this track since 1865 has
required 55,000 tons of iron, and 3388 tons of
steel rails. Thus already 18,000 tons of iron
rails have been renewed, and only three tons of
steel. The greater part of the iron rails re-
newed are of those delivered in the years 1865,
1866, 1868, and 1871, which have been the
worst, for of the 18,000 tons of iron rails re-
moved, 12,600 were of the rails laid during
these years. There have been broken 97 rails
in all — 94 of iron and 3 of steel. Comparing
these figures with the wThole number of rails of
each kind in the tracks, we find that 0.04 per
cent, of the total number of iron rails have been
broken, and 0.02 per cent, of the total number
of steel rails — that is, the number broken is in
the proportion of steel to two iron rails ; and
68.04 per cent, of the breakages have been at
the fish-bolt holes.
The Railroads op the United States in
1877. — From advance-sheets of Poor's
Manual (the eleventh annual number) we take =
the following:
RAILWAY .VOTES.
281
"The depression of the three previous years
still continues. Not only has there been a
considerable decline in the construction of
railroads, but the earnings also show a larger
relative decrease than at any period since the
first publication of the Manuil. The number
of miles of railroad opened during the year
1877 was 2177, against 2(557 for 1876, 1758
miles for 1875, and 2305 miles for 1874. The
largest number of miles built has been in New
York and Pennsylvania, and in narrow-gauge
lines in Ohio, Iowa, and Texas. No new lines
of any considerable magnitude have been under-
taken. The tables which follow will show in
what sections there has been any considerable
increase.
"The gross earnings of all the roads whose
operations have been reported have equaled
$472,909,272, against $497,257,959 for 1876
and $ 503,065,505 for 1875. The general result
of the operations of our railroads for the last
seven years is shown in the following state-
ment:
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" It will be seen by the above that the gross
earnings have fallen off $25,348,687, and the
net earnings $15,476,055, as compared with
1875.
"The ratio of net to gross earnings was 36. 16
per cent., as against 37.5 per cent, for 1876,
equal to an increase of 1.36 per cent, in the
operating expenses, as compared with the pre-
ceding year. The decrease in earnings from
freight has amounted to $ 18,278,154; and in
passenger traffic, $6,070,533; ihe percentages
of decrease being respectively 9.5 and 9.7 per
cent The dividends have fallen off $ 9,483,356;
and are less than for any year since 1871. The
total amount of capital stock on which divi-
dends were actually paid was $835,038,896,
giving an average rate of seven per cent. No
dividends were paid on any of the railroads in
the States of Arkansas, Colorado, Florida,
Kansas, Louisiana, Mississippi, Missouri, Ne-
braska, Oregon, Texas and Vermont — nor ex-
cepting on leased lines in Iowa and Minnesota.
"The principal decrease in earnings has
been in the Middle States, due partly to the
depressed condition of the coal trade, and
partly to the falling off in passenger earnings
as compared with 1876, the Centennial year.
"The elaborate tables heretofore printed in
the Manual are omitted this year; but the final
results, the only important feature, are given
in full detail. There is added a table reducing
these results to the unit of 100. From this it
will be seen that for each 100 miles of railroad
in the United States there are 22.8 miles of
second track, sidings, etc.; 20.1 locomotives;
15.2 passenger cars; 4.7 baggage, mail, and
express cars; and 495.3 freight cars of all
kinds.
"The capital stock aggregates. $2,921,507
for each 100 miles; the funded debt, $2,848.-
308; the floating debt, $300,078; and the total
cost of construction and equipment, $ 6,069,-
893; equal about to $60,699 per mile of com-
pleted road.
" The gross earnings per mile were, $ 6380.94;
operating expenses (63.85 per cent), $4074; net
earnings, $2306.90. Interest paid on bonds
per mile of road, $1248.04; dividends paid on
stock, do. $739.52. The ratio of interest paid
to total funded debt was 4.39 per cent; of divi-
dends to aggregate capital stock, 2.53 per cent.
In 1871, with only two thirds as many miles of
railroad in operation, and a little more than
one half the capital stock, the dividends
aggregated $ 56,456,681, equaling 4.19 per cent,
of the capital then invested. — Engineering and
Mining Journal.
It is but a few years since the idea of bridging
the Mississippi and Missouri rivers was held
to be both impracticable and outrageous, as
contemplating an infringements on the rights
of navigations, and terrible pictures were
drawn of the damage which would ensue to
the boating and rafting interests if a single
structure could be thrown over one of those
streams. But the locomotive could not be
kept back; one bridge was built and then an-
other, and now there are no less than eleven
structures — ten upon piers and one a pontoon
bridge — spanning the father of waters between
Winona and SC Louis. From a lengthy re-
282
VAN NOSTRAND7 S ENGINEERING MAGAZINE.
port from a United States board of engineers,
the Railway Age quotes the following list of
these structures and their sizes:
At
Winona
La Crosse ......
Prairie du Chien
Dubuque
Clinton
Rock Island
Burlington
Keokuk
Quincy
Hannibal
Louisiana
When
buiJt.
1871
1876
1875
"1808
1865
1871
1868
1870
1868
1871
187a
No. Longest
spans, span, feet. Draw.
16 . 240 . 160
. 240 .
Pontoons
240 .
180 .
250 .
200 .
240 .
160 .
240 .
256 .
10
14
7
10
12
24
8
11
160
160
118
160
160
160
160
160
200
ENGINEERING STRUCTURES.
THE Emperor of Brazil has recently written
an autogiaph letter to Mr. James B. Eads,
soliciting his advice in connection with the
contemplated improvement of some of the
great rivers in that country.
The Sutro Tunnel.— This remarkable engi-
neering enterprise will soon reach a suc-
cessful termination.
The famous Comstock lode has been worked
at a great expense, partly from difficult drain-
age and, partiy from the high temperature,
(120° F.)
Surveys made some years since indicated
that a tunnel, nearly four miles in length,
would lessen the difficulties and permit work-
ing to greater depths than would otherwise be
possible.
The State of Nevada, in 1865, granted to
Adolph Sutro the exclusive right for fifty years
to run the proposed tunnel. A contract was
made with all the leading companies, in which
they agreed to pay $2 per ton for all the ore ex-
tracted after the main tunnel is complete and
actually drains the mines; or, if they are not
drained, then after a lateral drift reaches any
mine. In 1866 the Federal Government
granted the right of way through the public
domain for seven miles along the Comstock
lode; also the right to select 1,280 acres of land
at the mouth of the tunnel, and the right or
title to the mines for 2,000 feet on each side of
the tunnel. All the mines of the Comstock
lode are made tributary to the tunnel, the same
as in the contract mentioned above. These
measures were carried in response to recom-
mendations and memorials signed by all the
prominent mining officials, bankers, etc., on
the Pacific Coast.
The tunnel has been in progress some eight
years, and not far from $3,000,000 out of
about $4,000,000 required to complete the work
and its railway connections have been expend-
ed up to this date.
Foundations for Bridges. — The system of
making foundations for bridges in marshy
soils, adopted by French engineers, in the case
of the Chareates Railway — a line which crosses
a peat valley to the junction of two small rivers
— seems to have solved the problem of what is
required in such cases. The thickness of peat
at this point was so great that any attempt to
reach the solid ground would have been ex-
tremely expensive. In order, therefore, to ob-
tain a good support for the bridge, two large
masses of ballast, accurately rammed, were
made on each bank of the river, and a third
on the peninsula between the two. The slopes
of these heaps were pitched with dry stones,
for preventing the sand from being washed
away by the rains or by the floods in the
rivers. Over the ballast a timber platform was
laid, this platform carrying the girders of the
bridge, which has two spans about sixty feet
each. When some sinking down takes place
the girders are easily kept to the proper level
by packing the ballast under the timber plat-
form— this platform packing being made by
the plate-layers with their ordinary materials.
In another case — that of a railway in Algierg
— a different plan of engineering was resorted
to. This road crosses a peaty plane nearly a
mile broad, the floods and elasticity of the
ground preventing the formation of any em-
bankment. The road was to be carried over a
viaduct across the valley, but the foundation*
of this viaduct presented serious difficulties,
the thickness of peat or of compressible ground
being nearly eighty feet. It was quite possible
to reach the solid ground with cast-iron tubes
sunk with compressed air, or any other system;
but neither the implements, the workmen, nor
the material for such an undertaking were ac-
cessible in that region.
Under these circumstances, the engineers
began boring holes ten inches in diameter down
to the solid ground; these holes, lined ^ith
thin plate iron pipes, were afterward filled
with concrete up to the very level of the
ground. Each of these concrete columns bears
a cast iron column, these columns being braced
togethei in a suitable manner, thus supporting
the girders of the viaduct. — Railway Review.
Wire Tramway Worked by Water
Wheels. — The tramway connecting the
town of Lausanne with its harbor Ouchy, on
the lake of Geneva, consists of two lines of
rail, and two trains which are connected by a
wire rope. At the rop of the tramway the rope
passes over a winding drum, through which
the trains are put in motion. The two trains
keep each other in equilibrium, the one ascend-
ing upon one line while the other descends on
the other line, and vice versa.
The tramway is 1,650 yards long, and leads
in a straight line from Ouchy up to Lausanne,
passing on the way a tunnel several hundred
yards in length. The steepest gradient is 1
in 9.
The winding drum is driven by two Girard
turbines, which work under a head of 393 feet;
they are made of brass on account of the high
velocity of the water, due to the great^ head;
they have a diameter of seven feet four inches,
and run at a speed of 170 revolutions per min-
ute. The water can easily be turned on and off
the turbines by means of circular slides worked
by hydraulic gear.
The two turbines are fixed upon a horizontal
shaft, which carries also a brake wheel, the
band of which is worked by gears similar to
ENGINEERING STRUCTURES.
283
the slides, and spur gear for transmitting the
motion to the winding drum.
The winding drum is 19 feet 8 inches in di-
ameter and 13 feet long, and is covered with,
wood lagging. As it has to transmit by mere
friction a force 180 H.P., making at the same
time only a few revolutions per minute, the
following arrangement to produce the necessary
friction has been contrived by M. Callon, the
designer of the tramway : The winding drum
is placed in a position parallel to the direction
of the tramway and considerably lower than
the level of the rails ; the rope is wound on the
drum in two coils, and above the drum ; the
two ends of the rope are made to pass over two
guide pulleys, which stand at right angles to
the drum, and are carried in sliding bearings.
By means of bevel gear and screw spindles,
these pulleys are made to move to and fro
along the winding drum, thus forcing the rope
to travel continually from one end of the drum
to the other, and preventing the surface of the
latter from being worn smooth, as it would be
if the coil were always on the same spot. —
Review.
Public Works in France.— M. de Freycinet,
Minister of Public Works, is an able and
ambitious man, and has lost no time in framing
a project which was well calculated to excite
the imagination of the French people. At the
close of 1877 he had developed his plans, and
on the 2d of January a project was laid before
the Marshal President, which proposed to ex-
pend one hundred and twenty millions sterling
upon the development and reorganization of
the railway system in France. Nor was this
all. Some days later a supplementary project
was presented, demanding the expenditure of
an addiiional forty millions sterling upon
canals. An expenditure of one hundred and
sixty millions sterling would be an arduous en-
terprise for even the most wealthy and actively
prosperous of countries, but in a country which
has been so depleted of capital as France has
been within the present decade, it is a proposal
demanding peculiar courage and coolness in
tho>e who make it. As must have been ex-
pected, it was assailed, not only by M. Rouher
and others in the interests of the monopoly
which the existing great companies practically
enjoy, but by some advocates of the smaller
companies, who are anxious to make better
terms for their clients. M. de Freycinet's
answer is practically a plea in " confession and
avoidance." He admits that if the whole sum
of 160 millions sterling were to be withdrawn
at once from active use, and sunk in the con-
struction or working of unproductive railways,
the danger of a financial crisis might become
imminent, but he points out that the expendi-
ture will be gradual — will be spread, indeed,
over ten years or more. Six commissions —
one for each of the reseaux worked by the great
companies — have been appointed \o inquire
whether the main systems of each of tnose
companies may not be extended, and in a few
weeks it is anticipated that they will have pre-
pared their reports. When they have reported,
the Ministry will be able to state with fair pre-
cision what the extent of the national railway
j system will be. The conjectures of well in-
! formed persons ave to the effect that the Minis-
l try, after the above-meniioned reports have
: been received, will state that provision must be
; made on national grounds for the maintenance
; of some 38,000 kilometers of railway in France.
I Of these "national lines" only about 21,000
| kilometers are at present in working order;
[ 5000 kilometers have been sanctioned by the
• Chambers, and private enterprise has under-
; taken 2000 more. But supposing all these pro-
' jects to be carried out, there would still remain
a deficiency of from 8,000 to 10,000 kilometers,
for which new and additional provision must
be made. In the same way, M. de Freycinet
j contends that the extension of the canal system
! ought to be provided for, and the reports of
five commissioners appointed to inquire into
j the artificial water* ays of the five gr at
\ " catchment basins " of France will ultimately
guide the Chambers. An expenditure of 30
! millions on new canals and on the completion
| of old work, and of ten millions on the deepen-
i ing and improvement of ports — such is the out-
: line of M. de Freycinet's scheme, of which the
' bill now before the Chamber of Deputies is
I only the first and most modest installment. As
for the financial plans with which the Minister
I of Public Works hopes to meet the new bur-
! dens he would impose upon his country, they
! are important enough to require separate con-
i sideration. It is enough to say now that they
[ would involve the addition, according to M. de
! Freycinet's calculations, of seven millions
| sterling a year to the taxation of France. — The
I /Standard.
ORDNANCE AND NAVAL.
New Gattling Guns. — Mr. Ackers, agent of
Dr. Gattling, inventor of the mitrailleuse,
tried at Sealand Range, Chester, recently, in
the presence of Captain Rogers and a number
of officers and men connected with the pen-
sioners now up for training, three new patent
Gattling guns, which have never before been
j tried in England. The mitrailleuses were first
I tried at 1000 yards range, Mr. Ackers working
! the machine. When everything had been ar-
i ranged, the signal was given, and the weapon
i literally poured out a hail of bullets, the ina-
j jorit}7 of which struck the canvas target and
tore it all to shreds, and penetrated quite
through 2-inch oak supporting poles. Accu-
rate time was kept by Captain Rogers, and it
was ascertained that the mitrailleuse fired 1000
I rounds a minute, which is 300 to 400 rounds a
j minute faster than any other Gattling gun.
I Experiments with the weapon were then tried
! at 800 and 600 yards range, and the way in
! which the bullets were hurled at the target,
and the marvelous precision with which they
{ struck it astonished every one present. The
! sergeant-major who was working it said that a
j sparrow must have been killed Hying across the
j line of fire: the bullets which fell a litt'e short
j tore up the clods of earth and hurled them
right over the target into the workmen's retreat.
It was the opinion of competent judges that
this is the most destructive weapon ever in
i vented.
284
VAN NOSTRAND'S ENGINEERING MAGAZINE.
The Loading of Heavy Guns. — To facili-
tate the loading; of heavy guns it has open
of advantage to enlarge the bore at the muzzle
by half an inch or more by scooping out half
an inch or so of metal for a depth of about two
inches. This process is to be termed "bell
mouthing," and it is to be applied to all the
guns in the Service of ten inches and upwards.
Artificers are being sent in various directions
to make the alterations in the guns at the
several forts and stations.
A New Explosive. — It was stated at the last
meeting of the Royal Dublin Society that
a new explosive agent has been discovered by
Professor Emerson Reynolds in the Laboratory
of Trinity College, Dublin. It is a mixture of
75 per cent, of chlorate of potassium with 25
per cent, of a body called sulphurea. It is a
white powder, which is very easily prepared
by the mixture of the materials in the above-
named proportions. The new powder can be
ignited at a rather lower temperature than or-
dinary gunpowder, while the effects it produ-
ces are even more remarkable thon those caus-
ed by the usual mixture. Dr. Reynolds sta es-
that his powder leaves only 45 per cent, of
solid residue, whereas common gunpowder
leaves about 57 per cent. It has been used
with success in small cannon, but its discover-
er considered that its chief use would be for
blasting, for shells, for torpedoes and for simi-
lar purposes. Dr. Reynolds pointed out that
one of the advantages this powder possesses is
that it can be produced at a moment's notice
by a comparatively rough mixture of the ma-
terials, which can be stored and carried with-
out risk so long as they are separate. The sul-
phurea, the chief component of the new ex-
plosive, was discovered by Dr. Reynolds about
ten years ago, and could be easily procured in
large quantities from a product of gas manu-
facture which is at present wasted.
Anew Italian Ironclad. — The ironclad
Dandolo, which was launched at La Spezia,
on Wednesday, is a sister ship of the Duilio,
now completing for seas for the Italian Govern-
ment- Both of them are to be armed with 100-
ton guns, and destined to carry armour no less
than 22 inches in thickness; so that, in point of
armament, these Italian men of -war bid fair to
be the most formidable afloat when they are
finished. Our Inflexible will not be so heavily
armed as either the Dandolo or Duilio for her
turrets are fitted to contain each of them a pair
of 80- ton guns, while the metal of the Italians
consists of four 100-ton cannon. On the other
hand, the iron walls of the British ship are a
little stouter, being 24 inches instead of 2i
The Italian armor was devised to keep
out shot from any cannon of less power than
that carried by the ship itself, and this the
plating practically does. The Duilio armour
is capable of repelling all shot with the excep-
tion of that from an 80-ton or a 100-ton gun.
The penetration of a o8-ton gun, the heaviest in
our service at this moment, is set down at 19|
inches at a short range, and with the employ-
ment of a battering charge, and ihe Duilio, has
its turrets protected with 22 inch plates. On
> the other hand, the 80-ton gun would make as
little difficulty in getting through 22 inches of
iron as 24, and there is little doubt nothing less
than three feet of iron can be depended upon
to stop the terrible blow of f ton of metal
hurled through the air at a speed of nearly a
mile per second. The Italians have not been
daunted, however. They have already set to
work, and are now constructing two ships to
carry armour plating capable of resisting any
gun in existence. They hope to build a pair
of turret vessels armored with 2 feet of solid
iron, and to carry cannon of perhaps 200 tons.
The names of these stupendous floating struc-
tures are the Italia and the Lepanto, but in the
meantime Italy possesses in the D mdolo and
Duilio two men-of war destined to carry
heavier metal than any ship in the British
Navy. The Dandolo was planned by the
Commendator Brin, the ex- Minister of Marine
The plates were constructed by Schneider of
Creusot, and the engines by Maudslay, of
London.
The New Field Gun. — The new field-gun,
which had, by a course of experiments ex
tending over more than two years, undergone
an evolution from a 9-pounder to a 12-pounder
without enlarging its bore or materially in-
creasing its weight, has undergone a further
and final development, and may shortly be ex-
expected to appear as the model field-piece of
the British Artillery in the shape and weight
of a 13 pounder. Experience has proved that
much of the value of a good field-gun lies in
the length of barrel, and accordingly the
13-pounder, although no thicker than a 9-
pounder, will be considerably longer than even
the 16-pounder, the heavy gun of the field
batteries of artillery, the efficiency of which
is now admitted to have been sacrificed to the
prejudice which existed at its introduction
against impairing its symmetry by elongating
the muzzle. The 13 pounder has undergone a
rigid course of experiments. It is a compound
of all the recent inventions, and it has pro-
duced splendid results.
Shell Penetration — Some trials of shell
penetration of a very important character
have lately been conducted at Shoeburynesa
under the direction of a committee appointed
for the purpose. The experiments were in the
nature of a competition between the shells of
different makers, and hence, as they are to be
resumed, it is not thought desirable that pre-
cise details should be published concerning
them until they are completed. The general
results obtained up to this point may be briefly
stated. The object was to ascertain what
shell would combine with the greatest power
of penetration the power to retain its bursting
charge in a state of efficiency. For this pur-
pose the most eminent firms in England and
on the Continent were invited to supply six
shells each for a 9-inch Woolwich gun, the only
restriction being that they were all to be of
the same exterior and interior dimensions, the
material and mode of manufacture being left
to the discretion of the makers. Five English
and four foreign firms entered into the com-
petition, and three varieties of projectiles were
sent from Woolwich— an ordinary Palliser chill-
ORDNANCE AND NAVAL.
285
€d iron shell, an improved chilled iron shell, and
shell made from the much-extolled Gregorini
iron from Italy. The gun used was an ordin-
ary 9-inch Woolwich, with a charge of 65
pounds of powder, giving a striking velocity
of 1500 feet per second. Every possible care
was taken to obtain uniformity of strength
and character in the plates fired at. These
plates were made by Brown & Co., of Sheffield,
were 12 inches thick, and of excellent quality
throughout. Each of them was divided into
pieces 4 feet square, and each competitor had
a separate piece to fire each shell at. Each
competitor fired two shells and the general
result was that both the steel shells supplied
by Sir Joseph Whit worth & Co, passed com-
pletely through the plate, and were left parti-
ally uninjured. All the others, especially I
those supplied by Herr Krupp and Herr Grusen |
wore broken to pieces by the impact, except j
the shells of the (French) Terre Noire Company
which proved to be so soft that they bulged,
and consequently retained so little penetrating
power that the back of the plate was but little
damaged. In every case, therefore, excepting
that of the Whitwcth steel, the projectiles
were found to be valueless as shells for the
purpose of penetrating armor and of retaining
their bursting power after penetration.
Quick Steaming. — The famous torpedo boat
Lightning, built by Messrs. Thorneycroft,
has been beaten at last. Recently a trial was
made by two launches constructed by Messrs.
Yarrow & Co., of Poplar, for the Admiralty.
The trials were carried out under the super-
intendence of Mr. Neil M'Dougall for the Ad-
miralty. The boats are each 85 feet long, 11
feet beam, and draw 3 feet. They are strong-
ly constructed of steel, and are fitted with
compound surface-condensing engines capable
of indicating 420-horse power. The high pres-
sure steam cylinder of these engines is 12|
inches in diameter, and the low pressure 21-|
in., both having a 12 inch stroke. These boats
are at present known by their builders numbers,
one being No. 419 and the other No. 420.
The former is propelled by a three-bladed
screw, 5 feet 6 inches in diameter and 5 feet
pitch; and the latter by a two bladed screw of
similar proportions. The trials were made
over the measured two miles at Long Reach.
No. 420 was first tried, and made the down run
over the two mile course in 5 minutes 19 sec-
onds, which is equal to a speed of 22.59 knots
per hour. In other terms, this vessel attained
the remarkable speed of 26 miles an hour.
She had six tons of ballast on board, and her
draught forward wTas 2 feet 8j inches, and aft,
2 feet 7 in' lies, Her mean revolutions were
460 per minute; maximum, 475; steam pressure
120 pounds; vacuum 23 inches to 25 inches and
blast 4 inches. The tide had just turned and
was running out, being, therefore, with the
vessel on the run down. On the run up it was
of course against her. This run was made in
6 minutes 47 seconds, or equal to a speed of
17.69 knots per hour. The mean of the two
runs was 20.14 knots, or 23.2 miles per hour.
On the up run the mean revolutions were 460
per minute; the steam pressure 120 pounds; the
vacuum, 24 inches; and the blast 4 inches.
The vessel was under way just an hour, during
which time she burned 10 cwt of ^oal, a por-
tion of which was used in getting up steam.
No. 419 was then tried. She was run light
without any ballast, her draught forward be-
ing 2 feet 5 inches, and aft 2 feet 4 inches.
The first run was made up the river, and, con-
sequently, against the tide. The two miles
were run in 6 minutes 38 seconds, giving a
speed of 18.09 knots per hour. The mean revo-
lutions were 459, the steam pressure 110
pounds; the vacuum 22 inches, and the blast
4£ inches. The second run was made down
the river, and, consequently with the tide.
Here the two miles were accomplished in 5
minutes 1 second, giving a speed of 23.92 knots
or more than a knot faster than any run made
by the Lightning, or 27.56 miles per hour.
The mean of the two runs was a speed of 21
knots, or 24.2 miles per hour. On the last run
the mean revolutions were 459, the steam
pressure, 110 pounds; the vacuum 22 inches,
Mid the blast 4 J inches, This is by far the
highest velocity ever obtained by a boat or
ship of any dimensions or under any con-
ditions.
Torpedo Warfare. — A remarkable series
of experiments has just been concluded at
Cherbourg by the successful completion of the
three hours' trial of the last of a set of six
torpedo vessels, which Messrs. Thornycroft &
Co. have just delivered to the French Govern-
ment. These vessels are somewhat similar to
the improved " Lightnings" which that firm is
now building for the English Admiralty, being
87 feet long over all, by 10 feet 6 inch beam,
and drawing about 5 feet 6 inches of water.
They are made of thicker plating than the
original Lightning, and differ from her also in
having the rudder placed abaft the screw — an
arrangement which it was feared would occa-
sion a considerable loss of speed in the vessels,
and which was only introduced at the urgent
request of the French Government. By some
what modifying the construction of the hull
and introducing some improvements in the
machinery, which practically secured an in-
crease of available power, this fear, as will be
seen from the following statement of results,
has been completely dissipated, and the boats
have in some cases attained a higher speed
than the Lightning did on her trial. The re-
sults actually obtained were as follows:
No. Speed on Speed on
of Measured three hours'
Boat. Knot. Run.
Knots. Knots.
54 .. 18.482 .. 18.661
55 .. 19.423 .. 18.734
56 .. 18.441 .. 18.963
57 .. 18 379 .. 18.165
58 .. 19.152 .. 18.405
59 .. 19.307 .. 18.836
The runs on the measured knot, six in number
for each boat, were made alongside the break-
water at Cherbourg, and the three hours' runs
were made in the open sea between Cape la
Hogue on the one hand and Barfleur on the
other. The difference of speed as ascertained
are accounted for by the condition of the bot-
286
VAN nostrand's engineering magazine.
toms of the boats and the state of the wind and
sea on the days of trial. The speed contracted
for was 18 knots per hour, so the contractors
have amply fulfilled their obligations in that
matter. The consumption of coal at full speed
was found to vary from 18 cwt. to one ton per
hour, and the bunkers were capable of contain-
ing five tons of coal. The actual amount of
coal carried on the trials was only that required
for a three hours' run. Steaming easily, the
consumption was found to be very light — one
of the vessels, having made the voyage from
Chiswick to Cherbourg in 22 hours on a con-
sumption of 2£ tons of coal. The weight on
hoard, in addition to the three tons of coal re-
quired for steaming, consisted of a crew of
ten men, with stores, &c, including even a
spare propeller and a weight equivalent to the
weight of the torpedo gear to be used on the
vessel, and fixed in the position that the gear
will occupy when the vessel is on service.
The primary object of the French in having
these particular boats is, of course, the defence
of Cherbourg; but it does not require a great
amount of foresight to perceive that boats
which are capable of steaming from one end of
the Channel to the other and still having coal
for a two or three hours' run at full speed will
not be confined to the defence of any particular
port, but will, in conjunction with larger ves-
sels, be employed in offensive operations which
will leave little to be done in the way of actual
defence. Engineers and stokers accustomed
to other classes of engines and boilers find
some difficulty at first in getting the power,
and consequently the speed, which Messrs.
Thornycrcft & Co.'s men obtain; but this is
mainly a matter of practice, and the French
officers of the "Defense Mobile" are most
assiduous in their efforts to acquire information
regarding their new boats, and to practice
their men in the working of them. Organiza-
tion is principally what is now required to con-
rert these boats, when properly armed, into a
most important means of national defence;
and the well-known ability of the French in
this way may be safely trusted to supply that
want, so far as they are concerned — Times.
Composite Armor Plates. — In continuation
of the Admiralty experiments with armor
plates, a composite plate, manufactured by
Messrs. Cammell & Co. of the Cy< lops Works,
Sheffield, was subjected to gunnery tests on
board the Nettle target ship, at Portsmouth
Harbor. The experiments are to determine
whether steel or composite pktes, that is
plates made with iron and steel, cannot be
made of greater inpenetrability than the iion
plates with which our war vessels are now
coated. Already nearly a dozen plates have
been in competition and notwithstanding each
has represented from 300 pounds to 500
pounds the results obtained have not been alto-
gether hopefull. The first experiments took
place in the presence of a distinguished com-
pany including the Directors of Naval
Ordnance and Naval Construction, and repre
eentatives of the German, Italian and Russian
navies. Since that occasion, however, the
experiments have been conducted in private,
being only attended by practical delegates of
the Admiralty able to gauge results of the trials.
The above-mentioned p'ate was 8 feet long by
6 feet 8f inches in width, and 9 inches thick,
its weight being slightly over eight tons. It
was composed of Si inches of steel, and 5£
of iron. The plate was fixed to a transverse
wood bulkhead built from side to side of the
ship, and consisting of two vertical and two
horizontal layers of oak bulks, making in all 3
feet 6 inches of thickness, the whole beiDg
shored by substantial wooden spalls secured by
a massive thwartship. The gun used was a
12-ton 9-inch muzzle-loading "rifle, and stood
behind thwartship wooden bulkhead 30 feet
from the plate. The charges were 50 pounds
of battery pebble powder, and the projectiles
chilled Palliser shots, 251 lbs. in weight, the
muzzle velocity being 1420 feet per second,
and the energy at the muzzle 348G feet. Three
rounds are usually fired at a plate and hither-
to that number has done inevitable damage,
but this plate was so comparatively invulner-
able as to lead to two extra shots being fired to
ascertain whether it was possible to break it
up. The impact of the first three shots formed
a triangular diagram, being about 2 feet apart.
The first projectile struck the plate on theritjht
hand side and penetrated nearly 7 inches,
occasioning a series of superficial cracks.
The impact of the next shot was on the lower
section of the plate the penetration being a
trifle more than 7 inches, and the further in-
jury a fissure gradiating to the bottom of the
plate, going quite home to the backing. The
third shot made a number of cracks insignifi-
cant in their character, and penetrated 6^ inches,
I he depth of penetration needs to be explained
for to those unacquainted with the previous
experiments the idea may be conveyed that
these tests were rather a failure. At ten yards
distance, with so powerful a gun as a 12-ton
9-inch rifle, a shot penetrates clean through an
iron plate, and partly through the backing,
and in a lesser degree the same result has at-
tended the experiments with composite plates,
excepting in the case of that manufactured by
Sir Joseph Whitworth, which was an extra-
ordinarily expensive one, being studded with
intensely hardened steel plugs. The fourth
shot was aimed at the center of the triangular
diagram, and partially broke the plate in two,
the width of the fissure being f of an inch-
Neither part, however, came away from the
backing. The fifth projectile struck the right
hand lower corner of the target and carried
away the section bodily. All the five shots
were smashed to fragments by the concussion^
only their heads being imbedded in the plate.
The experiments- were conducted by Captain
Herbert, of the gunnery ship Excellent. On
Tuesday two more iron plates were received at
Portsmouth Dockyard, one measuring 12 feet
8 inches by 4 feet 6 inches, its thickness being
10 inches, whilst the other's dimensions were
10 feet 5 inches by 4 feet 1£ inches, and its
thickness only 2 inches. The former plate was
manufactured by Messrs. Brown, of Sheffield,
but the latter bears no maksr's name, although
it is understood to have been forwarded by the
same firm. Immediately after the receipt the
BOOK NOTICES.
287
dockyard authorities telegraphed for instruc-
tions as to whether the plates were to be at
once fixed into position for gunnery experi-
ments.
BOOK NOTICES,
GEOGRAPHICAL SURVEYING: ITS METHODS,
Uses and Results. By Frank De Yeaux
Carpenter. New York: D. Van Nostrand.
Price 50 cts.
This book is No. 37 of the Science Series.
It is a report prepared originally as a part of
the labor of a Commission for the Survey,
Geological and Geographical, of the Empire of
Brazil.
A complete discussion of the methods per-
sued in the survey of large areas is presented
in this little treatise.
The organization of the corps; the order of
prosecution of different branches of the work;
the comparative merits of different instruments,
and the methods to be employed to secure the
proper degree of completeness and accuracy
without needless expenditure of time, are
, treated with a degree of fu lness that leaves
nothing to be desired by anyone familiar with
the general methods of surveying.
The subject will interest many who are not
of the engineering profession, since the results
of the surveys of our great western plateau
have called forth such nattering compliments
from foreign scientific journals.
The Whitworth Papers. I, Plane Metallic
Surfaces; II, An Uniform System of Screw
Threads ; III, A Standard Diurnal Measure of
Length. By Joseph Whitworth, Esq., Man-
chester. Price 20 cts. For sale by D. Van
Nostrand.
These brief essays are all included in one
small pamphlet, which seems singularly dis-
proportioned to the importance of the topics
or to the eminence of the author.
Practical engineers, however, for whom these
papers are designed, generally regard brevity
in boobs with favor, and will find these essays
none the less acceptable because they are in-
expensive.
Railway Service : Trains and Stations.
By Marshall M. Kirkman. New York :
Railroad Gazette. Price $1.50.
This work treats of the composition and
movement of railway trains and the laws
governing the same, including an exposition of
the duties of train and stationmen. The prin-
cipal topics discussed are : The mysteries that
underlie the organization and movement of
trains; The different signals employed on dif-
ferent roads; Phraseology employed on English
roads; Technical terms of a railway service;
Classes and grades of trains and their move-
ment; Instructions to conductors, brakenien,
&c. ; Rules regarding passenger and freight
traffic; Austrian railways; English railways;
General regulations for the block system on a
double track road.
The work is well printed and will doubtless
be of good service in aiding to harmonize
different systems and improve in a general way
the railroad management of the country.
PROCEEDINGS OF THE INSTITUTION OF ClVIL
Engineers. — Excerpt Minutes.
The following papers have been received
through the kindness of Mr. James Forrest,
Secretary :
The Steam Navy, comprising papers on its
use, by Chas. Douglas Fox, M.I.C.E. ; James
Brand, A.I.C.E.; Henry Mitchell Whitley,
A.I.C.E. ; Charles Augustus Harrison, M.I.C.E. ;
also Remarks on Steam Excavating Apparatus,
by Ruston, Proctor & Co. *
Machine Tools, by Percy Ruskin Allen.
The Egremont Ferry-Landing, by William
Carson, M.I.C.E.
The Hooghlv Floating Bridge, by Bradford
Leslie, M.I.C.E.
Drainage and Cultivation of the Albufera
(Marshes) in Majorca, by Henry Robert Wa-
ring, M.I.C.E.
All the above papers, except the last, are
fully illustrated.
MISCELLANEOUS.
Soukce of Error in Leveling. — Mr. G. C.
Herron, Ottawa, Can., writes us as follows:
" I have not seen mertion made of the fact, in
any book on Engineering, that when leveling
over a hill or mountain the bubble will not as-
sume a truly horizontal position; but will be
at right angles to a line from its center to the
center of gravity of the general mass of the
earth and hill combined. This will cause the
line of sight to rise in going up a hill and to
fall in going down, and is a fruitful source of
error in correct leveling."
M. Bardoux has opened at the Palais du
Champ de Mars the Exhibition connected
with Public Instruction. The minister said in
his address that, owing to the recent progress
of France, that country was now inferior to no
other European nation as regards popular
education. The results of the last conscription
are highly satisfactory in this respect. Out of
294,382 men admitted into the ranks of the
French army in 1877, only 4,992 were unable
to read or write, 2,620 had taken their prelimi-
nary degrees in letters or sciences, 284,279
knew the "three R*s," 36,325 could only read
and write, and 5,856 could only read. Ele-
mentary schools have been established in the
various regiments of the French army for
years but the attendance, which had been
very limited, is now almost universal. Not
less than 305,989 soldiers were pupils of regi-
mental schools in 1877; out of these, 255,380
followed the course of elementary instruction^
36,981 the secondary course, and 4,682 the
course of superior instruction. The army has
been turned into a machine for promoting
elementary knowledge. In 1877 not less than
33,337 soldiers learned to read, 21,483 to write,
and 111,303 were taught arithmetic. Under
guidance of their officers, 200 soldiers from the
garrisons of Paris visit the Exhibition daily.
ii
The supply of ice in Bombay has failed,"
was the announcement which greeted
288
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the inhabitants of that city and the surround-
ing country about the middle of last month;
and no one who has not experienced a week of
life in India without ice can conceive the dis-
may with which the report was received. A
large trade in ice is carried on between India
and North American ports, Boston being the
principal place of shipment, and, with the spe-
cial arrangements made on board the vessels
for keeping down the temperature, it is found
cheaper to import it in this way than to make
it artificially. The man who can devise some
means of making ice by artificial means, in
large quantities and at a sufficiently low cost,
will make his fortune and confer an immense
boon on those whose fate it is to dwell in coun-
tries beneath the sun. A little enterprise
would probably open up a new field for the
supply of ice for India in the Antarctic regions
The lands and seas surrounding the South
Pole require exploration, and a vessel destined
to press the icebergs of that rtgion into the
service of the inhabitants of India would be
able to drive a lucrative trade, and at the same
time do science a service. It would hardly be
possible, perhaps, to take a giant iceberg in
tow, and haul it bodily into Bombay Harbor,
but with the easy means afforded by dynamite
of breaking up these floating monsters into
suitable sizes for stowing on board ship, the
neglected supplies might, thinks the Colonies
and India, be utilized with comparatively little
difficulty.
Lb Neve Foster Testimonial Fund. — Some
members of the S ciety of Arts, and
others, who know the history and progress of
the society during the last quarter of a century,
and feel how much of its success during that
long term has been due to the judgment, zeal
and devotion of its chief executive officer, the
secretary, Mr. Peter Le Neve Foster, have
associated themselves together to present him,
on the occasion of his completing twenty-five
years' service, with a substantial testimonial
in money, as an expression of their respect.
Mr. Foster became secretary to the Society of
Arts in 1853; the number of members at that
time was little over 1,000, and the annual
revenue scarcely exceeded £3,000; whilst in
the year 1877 the number of members was
nearly 4,000, and the revenue over £ 11,000.
A reference to its "^Journal" will show how
many are the important public questions with
which the society has successfully dealt during
this period, questions in the initiation and con-
duct of which Mr. Foster has taken a promi-
nent part. Education, elementary and techni-
cal, the reform of Jthe patent and copyright
laws, international exhibitions, public health,
Indian and Colonial topics— these are but a few
of the subjects on which Mr. Foster, through
his connection with the society, has done use-
ful work. On grounds such as these his
friends confidently appeal to the members and
to the public for their hearty co-operation. A
committee has been formed to receive sub-
scriptions, which may be paid to the credit of
the Le Neve Foster Testimonial Fund, at
Messrs. Robarts, Lubbock & Co., or at Messrs.
Cocks, Biddulph & Co., or to the honorary
secretaries and treasurers, at the offices of the
Society of Arts, John Street, Adelphi.
One of the most remarkable occurrences
which has come under our observation
lately is the disappearance of a locomotive and
tender beneath the quicksands of Kiowa Creek,
Colorado.
The circumstances are somewhat as follows:
An eastern-bound freight train on the Kansas
Pacific road, on the 21st of May, plunged at
full speed into the above named creek, the
bridge having been washed away by a flood.
The current was so strong that loaded cars and
iron parts of the locomotive were washed five
miles down stream, while- the locomotive and
tender disappeared altogether and were not
found for more than two weeks afterwards,
though diligent and constant search was made
with long iron rods and otherwise daily. They
were finally discovered, it is reported, by
means of a magnet, which was carried over
the surface of the sand and was finally
attracted by the hidden iron. They are fifteen
feet below the sand and twenty-five feet down
stream below the bridge. Specific gravity ac-
counts for the sinking of the locomotive
through the quicksands, but in our judgment
the movement down stream can only be ac-
counted for by supposing that the whole mass
of sand in the bed of the stream was in motion,
like a glacier, and that the combined weight of
the sand and the force of the current were
sufficient to force this ponderous mass of iron,
weighing peihaps twenty-five tons, the dis-
tance of twenty-nve feet' from where it fell.
It is calculated that water moving at a velocity
of 3,600 feet an hour carries fine gravel, and
when moving at a rate of two miles carries
coarse gravel and pebbles. Such being the
case, a stream moving with a velocity of not
less than five miles an hour in a bed of quick-
sand would doubtless move the whole mass
with almost irresistible force. It must be re-
membered that nearly all of the time, the year
round, the bed of the Kiowa is perfectly dry
and that all the water that flows through it
except during freshets, passes beneath the sur-
face of the sand, and it is not unreasonable to
suppose that the sand may thus be moved en
masse when suddenly saturated by a swift and
powerful stream. Doubtless the formation of
the canons of the plains may be, in part at
least, accounted for in this way. — Western
Review.
The commission for reorganizing the Ob-
servatory of Paris has — says Nature —
ended its sittings, as we have already reported.
The commissicners recommended no change in
the present organization of the Internal Mete-
orological Office ; but, taking into considera-
tion the actual wants of meteorology, it has
advised the Minister of Public Instruction to
appoint a meteorological commission, in order
to suggest any measures which might be
likely to promote the interests of meteorology
at large, without interfering with the working
of telegraghic weather forecasts sent by the
International Office to the sea-ports and more
than 1200 parishes all over Fratice.
VAN NOSTRAND'S
ECLECTIC
ENGINEERING MAGAZINE.
NO. CXVIIL-OCTOBER, 1878.-V0L. XIX.
MAXIMUM STRESSES IN FRAMED BRIDGES.
By Prop. WM. CAIN, A.M., C.E.
Contributed to Van Nostrand's Magazine.
III.
108. Let us now compare the weights
of the three trusses examined for the
most economical heights. As the diam-
eters of the columns are unchanged, the
same number of pounds of iron for cast-
ings <fcc, was added as before. The
section of the vertical posts in the
triangular truss was taken at 4.5 square
inches (see art. 8V).
The trusses are all of 200' span, with
12 panels. Assumed dead load 336,000
lbs ; live load 2,000 lbs. per foot, with
two 60,000 lbs. weights, not less than
50' apart, so placed as to give maximum
strains in chords and web. The trusses,
for the diameters of columns, strains per
unit &c, given, are of the most econom-
ical heights ; all of them being through
bridges with leaning end posts. The
following is the comparison of weights:
Truss.
Fig.
Height.
Weight in lbs.
Triangular ....
Whipple
Pratt
7
9
5
27
29
26
324909
325390
833086
The comparison is thus most favorable
to the Triangular, next to the Whipple,
and least to the Pratt Truss, for the
panel length &c, taken. Practically,
the first two have the same weight.
Vol. XIX.— No. 4—19
109. An increase of the diameters of
those columns that admit of it, would
probably benefit the triangular most.
Thus some of the interior posts of the
Pratt or Whipple Trusses admit of little
or no increase in diameter for a proper
thickness of metal, whereas the main
braces of the triangular do admit of it.
With diameters of 15" for upper chords
and braces, the triangular may give
the least weight ; supposing the diame-
ters of the upper chords of the other
trusses to be 15" also, the posts being
enlarged where possible. On the con-
trary the workmanship towards the
center of the space probably costs more
for the triangular than for the others.
The heavy competition in this coun-
try has been productive of economy in
material and workmanship, in bridge
building, and the "bids" on the same
design, often give the best comparisons
between trusses of different types and
details.
Each design has its advantages and
disadvantages, and as a consequence
its advocates and opposers.
A proper study of the details of truss-
es now before the country is then imper-
ative.
110. It is interesting to ascertain what
290
VAN nostrand's engineering magazine.
inclinations of ties and braces will make
the web material a minimum. Thus let
Fig. 12 represent a panel of Fig. 11.
Put AB=Z, AC=^, BC=£2, AD=*,
DC =/*/ the dimensions being in inches.
w" = weight of 1 cu. in. of tie BC in lbs.
w'=weight of 1 cu. in. of post AC in lbs.
c" = cost per pound of tie in cents.
c'=cost per pound of post in cents.
£=7500 (1 + #)= strain per sq. in. for tie.
38500 {! + &)
//
4 +
0d + r* + 10dr2
per square inch for post
as given by eq. (8), art. 53.
Fig. 12.
safe strain
We find, S being the shear on the
panel,
7 C7
Strain on CB = S72; cost CB=^.Ja*oV.
h lib
I S£
Strain on CA^Sy-; cost CA= z-^.lw'c'.
h lib '
Substituting for b and b' their values, we
have as the total cost of tie CB and post
CA,
A i
l + 0)h (
*>v +
100 (l + 6)h ( 15
1V 10« r2 10dr2/
__— 385
Placing lx = v77T?~; *\=V + (l-xf;
differentiating with respect to x and
placing the result =o, we lind that for
the least cost of tie and post (on replacing
308 w"e"l
?>0Sw"c" + 30w'c'(8 + -^i -f I6c-i + - L±-
Examples. — 1. Let w'fc"=w'c',
d
30,
and for a hollow cylindrical post hinged
1 „ c?2 r
at both ends c:
18000'
7200,
whence x=.26'l.
If c? is given, it is evident that h has
only one value corresponding to cc=.26 I
to be found from the equation - = 30 =
ri
.-. A=V(30^)2-a;2.
2. Similarly we find for-^:=20«=.36£;
and for j =40, a?=.18Z.
111. If for &1' we write Rankine's
formula with a constant factor of safety,
38500
o=h
P
l + c-V
and proceed as before to deduce a
formula, &c, we shall find by it that
for
\ =20, x=.36l
d
30, x=.3 I
40, x=.24l
If in a Pratt truss (Fig. 5) of 200' span,
the posts as well as the ties are inclined
so that x=%l, the web (neglecting the
counter braces) weighs a few thousand
pounds less than with vertical posts;
the posts regarded as hinged at both
ends in both cases. Using the value of
V in the previous article, for ^—30 as an
average, we found x=£l for greatest
economy. This is the value adopted in
the Post truss and is, theoretically cor-
rect, for the above value of b\ which is
agreeable to practice as before men-
tioned. The economy of the square
joint, however, due both to less work-
manship as well as the use of a formula
for posts with " flat ends " or " one pin
ends " eliminates all saving in this direc-
tion.
112. If the post is of wood w'c' is very
small compared with w"c" and x is nearly
equal to I. Hence in the Howe type
(Fig. 6) the braces should be of wood —
never of iron — for economy. Similarly,
if the post AC is of cast iron, x ap-
MAXIMUM STRESSES IN FRAMED BRIDGES.
291
proaches i I as its proper theoretical
value. The chords will influence the
above results very slightly for usual
diameters of upper chord.
113. For deck bridges and the trian-
gular through truss, the shear on the
post is greater than on the tie, and the
post should be more nearly vertical.
This supposition is easily included in the
formula.
114. Most Economical Depth for a
Fink Element. — Let a weight W act at
P, Fig. 13. Call the constant length,
BP=AP=£; the variable height of post
PC =jcy the strain per square inch on
ties AC, BC, = T, on chord AB = &', on
post PC = &. The weight W is directly
supported by the post PC.
Fig. 13.
Thus let T=b'= 10000,
6=10000, i=45°
b= 7000, 2=47°47'
b = 6000, i=4:9° 3'
b= 5000, i=50°47'"
b= 4000, i=52°5o', &c.
38500(1 + 0)
116. Regarding b =
as variable we find,
I
tan. i = — =
x
(^)('+f)
•
CX*
( x 12cx' 4
b'T ) 4 + 57/ + ~7~ + U) dr* 1
b' + T ( 38500(1 + 0) T
x
Decomposing W=DC at C, the strain on
AC or BC is £W sec. i=—-
This strain is in equilibrium at A or B
with the reaction JYV and the chord re-
• w/
sistance AW tan %=—-—.
2 x
On dividing the strain on each mem-
ber by its strain per square inch and
multiplying by the length of the mem-
ber in inches, we get its volume. Thus
the total volume of AC + BC + PC + AB
is
VV\ Tx
+
—)
xb'P
For a given — we can of course find
tan. i / but generally d is given and we
x
can not know -7 until x is found. Hence,
a
given c?, we cannot determine tan ?', ex-
cept by a series of approximations.
But as in the case of beam trusses,
having assumed x and di unless the pre-
ceding equality holds, the most economi-
cal depth has not been chosen, and the
formula will indicate whether x is too
small or the reverse.
Examples. — Let, V = T = 10000, and
let PC be a hollow cylindrical column
x* 8x'2 x* 8x\
' d2 ' dr9
and (9= J.
d3
Also place c-
24000
Then for,
x
d
20, tan. 2=1.237 .'. z = 5l° 3'
30, tan. z= 1.473 .: i=55°50'
to be a min.
Now T is constant; also b', since I is
constant, but b varies with x.
115. Regarding b as constant; on
differentiating, &c, we readily find, for
a min. vol.
x*\'V b' J T + b
fa
n. i= L = JQ+W
« y (b' + T)b
— =40, tan. £=1.761 .*. z=60o25'
d
Thus somewhat shorter posts are re-
quired than when b is taken constant.
117. Let us now investigate a Fink
truss (deck bridge) Fig. 14 for maximum
strains and minimum material. Assume
as before a 200' span, but divide it into
16 panels of 12£' each. As before, let
the weight of bridge = 33 6000 lbs., or
10500 lbs. per panel on one truss; the
car load, uniformly distributed, 1000 lbs.
292
VAN nostkand's engineeking magazine.
KiG. 14.
per foot or 12500 per panel for one truss,
and the locomotive excess, two weights,
30000 pounds each for one truss and 50'
apart, to be so placed as to give maxi-
mum strains on chords, posts or chain
system-
Each 30,000 pounds rests on 3 drivers
for one truss, 6' apart or a total wheel
base of 12' .-. there is 10,000 pounds on
each driver. Hence when the center
driver is at any post as c, the adjoining
posts bear — — 10,000=4800 lbs., and the
1 2.5
post c therefore 30,000—9600 = 20400
directly.
118. If a weight is placed anywhere on
acf since the element arc acts independ-
ently, the reactions at a and c are de-
termined by the law of the lever. Simi-
larly for the systems ase, ati, and auq ;
for the posts at the end of the system
act as abutments to the system consid-
ered, and the reactions can only be de-
termined by the simple law of the lever,
irrespective of the pattern of the chain
system used.
119. It follows, therefore, that the
max. strains on posts b, d, f . . . . =1
panel dead and car load, (23000) 4- 20400
of loc. excess (center driver bearing on
post) = 43400 pounds.
The dead load is really less as the
chains, at, au . . . only rest on cs, ct . . .
ordinarily, but the section of the post
would hardly be taken less than this
strain gives, owing to oscillation of en-
gine sometimes increasing the reaction at
b, d ... due to engine weight. But for
posts b . . . put (9=-— -Q=.13.
Next, let center driver bear at c.
The post c bears directly 23000 lbs.
car and dead load 4- 20400 loc. excess;
also 23000 4-4800 transferred from b and
d, making in all 71200 .'. Q — -~— =.3.
The post 6, bears directly 43400 4- -J
car and dead load at b, c, d and /, g, h,
(69000) + (2.|.4800 + £.4800) loc. weights
borne at d, f and h= 1 20800 lbs. if center
driver is at e ; but with locomotives at c
and g, post e sustains J load on a i=
122000 lbs. which is therefore its max.
strain; and 6=^%=. 34.
If locomotives are supposed at d and h,
the reaction at e due to them is (J + £)
30000 = 30000 as in the preceding case.
Lastly to find the max. strain borne
by post i. It bears 8 panels, car and
dead load (184000 lbs). With engines
at g and k, by art. 118, post i bears
£ 60000 loc. load. With engines at h and
I, i sustains £30000 + |30000=f 30000 as
before; but with engines at i and m, i
sustains £30000 + 2f 4800 + 20400 = 43800
or less than the 45000 before.
120. From the above we see that
when one locomotive only can get on the
system, it must be placed over the cen-
tral post of that system to find its max.
strains ; when two locomotives can bear
on one system they must be placed
either side of the central post.
The above strains are entered in the
following table. The max. strains on
the ties at the foot of the posts are found
by multiplying £ the max. strains on
posts by sec. i, i being the inclination of
the tie to the vertical.
The lengths and diameters of posts
are assumed as in the table.
It was not considered judicious to
make the center post i longer than 30
diameters, though for theoretical econo-
my it should be much longer.
121. Chord Strains. — As in art. 114,
to find the chord strain due to any ele-
ment we multiply £ weight at foot of post
by tan. i.
Thus for the uniformly distributed
car and dead load of 23000 lbs. per
panel, post b bears 23000 lbs ; post cb
46000 ; post e, 92000 and post i, 184000
lbs. Similarly for similar posts so that
the strain on a q, for uniform load is
the same throughout and equals
MAXIMUM STEESSES IN FRAMED BRIDGES.
293
Piece.
d
I
d
th
Strain.
e.
b.
Area.
Length.
No.
Jc.
1
; Weight.
Totals.
>>
n
□ "
/
lbs.
Post b
6
20
5
T7T
43400
.13
6400
6.8
10
16
10
3627
c
11
22
TIT
71200
.30
6950
10.3
20
8
5493
e
13*
30
*
122000
.34
5670
21.5
100
4
"
9555
i
18i
30
1
229000
34720
.37
.13
5800
8470
39.5
4.1
100
16
2
32
< (
8778
27453
Tie ar
6997
as
56960
.30
9750
5.8
32
16
( t
9898
at
109983
.34
10050
10.9
60.1
8
1 1
17469
au
131
11.3
1*
362049
485625
.37
.39
10420
10140
34.7
47.9
105.4
200
4
2
"
48765
83129
Chord aq
63867
63867
i(184000X3 + 92000X 1| + 46O0O
X||- + 23000Xli) = 388125 lbs.
122. Next consider the locomotive
excesses, 50' apart, consisting of 30000
lbs. each on 3 drivers. With center
drivers at g and k, these posts support
directly and indirectly 25200, the adja-
cent posts 4800 II is each (art. 117); e
and m, will bear 15000, and i 45000 lbs.
applying the simple law of the lever to
determine these reactions. This gives as
the total strain on the parts ei or im, due
to loc. excess
J(45000 X 3 + 15000 XH+ 25200§|-
+ 4800|5) = 97500 lbs.
Similarly, for engines at e and i, the
part ci experiences a strain of 92400 lbs.
which differs but little from the preced-
ing; hence I have regarded the chord aq
as strained throughout by £ 7500 + 388125
= 485625 lbs. as entered in the table.
With engines at c and g, the chord
strain on ai due to loc. excess is 86250
lbs. — less than in preceding cases.
123. The trusses were assumed 14'
from center to center; floor beams being
15. 5' long and 24" deep; the web, J"
thick. The loss in the rivet holes is
assumed equal in effect to the resistance
afforded by the web &c. The floor
beam max. live load is 63880 lbs. (see
art. 15), to which add 6738 lbs. dead
load. The moment at center is thus,
35309X54//=/$«=7500X24Xl0.6. The
section of a floor beam is thus, 28.5 sq.
in. and its weight 1472 lbs. Similarly
the stringers of wood, each 16" X 6.6
(see"Fig. 9) or of iron I beams, 16" deep,
weigh about 213 lbs. per foot. The
transverse bracing was put at 11400 lbs.
as for the Whipple truss, the rails and
cross ties as before. The " Whipple "
deck truss, (art. 91) with which this one
will be compared was subjected to as
near the same conditions as possible, ex-
cept that the panel length of the former
was taken at 16f feet, whereas a differ-
ent panel length might be more econom-
ical. The same percentages for castings,
bolts, &c, was added to both.
The following is the
Bill of Materials.
Fink Deck Bridge, 200' span, 16' panels.
lbs.
Ties 83129
15 p. c 12469
Chord and posts 91320
20 p. c 18264
Lateral tie rods and struts 11400
17 Floor beams, 24" deep 25000
Wooden stingers 42600
Rails, cross ties, &c 83200
Total weight of bridge. . . . 317382
Assumed weight 336000
Assumed weight too great by. . 18,618
124. Let us now ascertain if each ele-
ment of the truss has its most economical
depth.
For the element arc, we must substi-
tute in the value of tan. i (art. 116), T=
8500, £' = 10200, - = 20 and 6=. I'd, as
found from the table ; whence we find
that for the most economical depth - = 1.3
x
.-. for £=12.5, x=br=9.6 feet, As we
assumed br=10, the result is almost
exact ; in fact considering the thickness
of chord, it is practically exact.
Similarly for the element ase : T —
9800, 6' = 10200, 0=.3,-7=22 whence tan
294
VAN NOSTRAND'S ENGINEERING MAGAZINE.
i=~ =4 .*. for £=25, 3=cs=18.8 feet.
This value differs only 1.2 feet from
the 20 feet assumed, or really only .6
foot say, considering the thickness of
chord. The depth is very slightly too
great.
For the element ati, T= 10050 bf —
x
10140, =30 and 6 = .34, whence (see
a
2nd example, art. 116) -=1.473 .*. for /
= 50, x=et=33.9, we assumed 33.3.
Practically then, the most economical
depths have been chosen for all the ele-
ments excepting aitq, which is necessarily
circumscribed in depth.
125. The formula of art. 98 applies
directly to a Fink element, Fig. 13, since
the chord strain varies directly as tan. i
or as the depth, and the shearing force,
J W, is the same on the ties of Fig. 13
for any depth ; these being the only
requirements of the formula.
For a Fink element, Fig. 13, formula
(14), art. 98, takes now the following
shape,
Wc=Wtcos. 2i+Wv(l+m);
in which
Wc= Weight of chord A B
Wt= Weight of ties AC + CB.
and
Wp =Weight of post PC.
In the value of m, for hollow cylindri-
cal posts, hinged at one end,
I2 1(1
V2 3000 V d
)'.
Now for the element ati Fig. 14, i
= 56°19', cos. 2*= -.385.
From the table art. 120 we get 4 Wt=
17469, 4 Wp=9555; and computing
Wcwe find 4 Wc =(6l000X6-M0140)
x
iffi-= 12030. Also for -j=30,m=f + Jf ;
whence
4 Wc = 12030> 17469 X— .385
+ 9555(l+f + it) = 11235
The chord weight is very slightly too
great, which indicates that the depth is
too small for the most perfect economy;
the same conclusion previously arrived at.
On comparing now the weight of the
Fink with that of the Whipple deck
bridge, {art. 91), we see that the Fink is
lighter by 10,072 lbs.
126. Fink Through Bridge. — If we
draw a line tu (Fig. 14) parallel to chord
and drop " suspenders " from the foot of
posts, as r, #, . ... to hold up the roadway
tic, and also add vertical posts at a and
q, the depth of the truss, we have an
outline drawing of the Fink through
bridge. Call the points of the roadway
vertically under a, b, c, . . . . respectively
a', b', c! . . . .; and consider the element
arc conjointly with the suspender rb' for
economy. Call br=x, bbf=h .'. rb'=
(h—x). As the post br only supports
one panel upper chord, &c, its section
will practically be taken much larger
than the 2500 pounds about of dead load
requires. Hence we can regard its
section = S constant as br varies in
length.
As in art. 114, call the strain per
square inch on ties (ar, re, rb'), T; on
chord, b' . Then we have as in art. 114
the total volume of ar, re, b'r, ac and br
(calling W=load on suspender b'r),
nr/x' + l2 h-X P\ a
whence,
cp. hr f
b'TS
W(ft' + T)
Now putting S=4.5, £'=10000, T=8500,
W= 43400, it follows that for economy
that x=l-r-.685. Thus if 1=12.5, x=br
= 18. For S=10, <e=12.5 feet, &c.
The first values (nearly) are taken from
the following table, and the results are
thus correct for the element arc : but in
the element ase, the cross section of cs
must not be assumed constant for differ-
ent depths. If it were, then it follows
that for 6'=10,000, T=9700, W = 71200
and S=8 that l=% x .'. 3=33.3 feet=cs.
For S=14 (about), x=l.
It is easy to deduce a formula regard-
ing b for the post sc as varying, but it is
perhaps simpler to determine the proper
value for sc by trial. From the formula
above we see that as S diminishes, that
the angle between the ties becomes less.
127. Let us assume as before that the
ties ar and as are equally inclined, but
place their inclination now at 45°, the
depth of truss, no. panels, &c, being as-
sumed as before.
MAXIMUM STRESSES IN FRAMED BRIDGES,
295
The maximum strains on ties and top
chord are determined as before, since
they depend only upon the load borne at
the foot of each post, whether that load
is communicated by posts or suspenders
or both.
The chord strain due to uniform car
and dead load
=-£(1 84000 X 3 + 92000 X lj + 46000 +
23000) = 379500;
and that due to loc. excess placed at g'
and k'
= ijf (45000 X 3 + 15000 X l£ + 30000) =
93750
The sum of the two is entered in the
following table. With engine at b', post
c bears about 41000 pounds. The posts
e and i bear, one panel of car load
(12500) + one panel roadway (3535), or
16035 pounds less than before, giving the
max. loads ever borne by
Post e, 122000—16035 = 105965
" *, 229000 — 16035 = 212965
The dead loads carried by these posts
are 17465, 38465 and 80465 so that 6 has
the respective values, 42, 36, 37.
The suspenders bear 32900 lbs. live
load (=20400 + 12500) and 3100 lbs.
roadway : in all 36000 lbs.
Piece.
Chord
Post br
C8
et....
iu
Suspenders
Tie ar
as
at
au
m
5
n
13*
l|th
d
11.311,
i
4
Strain. 0.
473250 |.39
2500 1 .
41000 .42
105965 .36
212965 .37
36000 .13
36000 1.13
43400
30727
.13
8470
50410
.3
9750
109983
.34
10050
362049
.37
10420
10140
4880
5750
5800
8470
8470
Area.
Length.
No.
k.
Weight,
lbs.
Totals.
D "
f
46.7
3.6
200
12.5
2
16
3
62267
62267
2400
8.4
25
8
1
5600
18.4
100
4
8180
85.5
4.3
1 00
3
20.8
o
16
"
7889
24069
4770
4 3
3.6
8.3
17.7
8
32
"
952
5722
6797
5.2
35.4
16
" i
9818
10.9
60 1
8
»
17469
34.7
105.4
4
"
48765
82849
128. With trusses 16' apart, center to
center, the iron floor beams, 26" deep
are estimated to weigh 1866 lbs. weight
per panel; stringers and track as before
4738 lbs. We now form the following :
Bill of Materials.
Fink through bridge, 200' span, 16 panels,
33'. 3 deep.
lbs.
Chain system and suspenders "88571
15 p. c. for bolts, nuts, eyes and pins 13286
Chord and posts 86336
20 p. c. for castings 17267
Floor beam loops 5000
Lateral rods, struts and portals. . . . 15000
15 floor beams (26" deep) 27990
Stringers (of wood) 42600
Rails, cross ties, &c 33200
Total weight 329250
Assumed weight 336000
The lateral struts and portals were
increased over previous trusses examined
by 4600 lbs. on account of the greater
depth of this truss. The roadway for
greater stability, should be formed of
closely spaced cross bearers, extending
from truss to truss, but we have estima-
ted as above. If we subtract the weight
of portals, say 5000 lbs. we get the weight
of bridge for calculation 324,250 lbs.
The four-end posts or " pier towers,"
are 33.3 feet high and for 30 diameters
weigh in all 17111 lbs. since they sustain
a max. load of 226500, when train
extends from farthest abutment to near-
est panel. These pier towers should be
given a broader base for equal stability
with other trusses, and hence should
weigh more than the above. Putting
them at 17111 the total weight of bridge
and towers is 346,361 lbs. which is more
296
VAN NOSTRAND7S ENGINEERING MAGAZINE.
than for the Pratt, Whipple or Triangu-
lar, previously examined.
129. To ascertain if the most econom
ical depth has been chosen, let us keep
the inclination of the ties, inclined 45,° at
that angle. Then for a change of height
A h, only the suspenders, end posts and
weights, due to systems auq and ati,
need be examined. Call ws = weight of
suspenders of height r#'=20.8=b1 then
if the height of the truss h = 33.3 is
increased by A A, the new weight of sus-
penders is
h. + A h Ah
w^—^ji — =ws + ws—
Similarly the new weight of the other
suspenders whose height=A2 = 8.3 is
,AA
~K
If these expressions are added to the
value of F(h+ Ah) in art. 98, and the
subsequent reductions made as in that
article, (the transformations the above
terms undergo are very easily traced), we
find in place of eq. (14) that for the most
economical height,
/+Ws
W, =■
,h
+ Wa ' -j- + ^w (cos. 2i + -rj m)
ni A2 t
130. In this formula wc —weight of
chord due to variable elements ati and
auq=5573<i lbs. The posts et, ia and
end posts being all 30 diameters long and
A2
vertical, cos. 2z'=l,— = 1, m=f + J-f, and
their weight Wp =16069 + 17111 = 33180
lbs.
The weight of ties, at, ti, . . . , inclined
at 56° 19 to the vertical is wt = 17469.
For them cos'. 2i= — .385. The w't. of
au icq=tot ' — 48765. For them cos. 2i=
— .6. Also io6 =4770 and w$ ' = 952.
Now if the most economical height has
been chosen we should have
Wc =we-j- +w8' -T- +Wt X(-.385)
K K
+ Wt,(-.6) + Wp(l+m).
Actually we have,
Wc =55732>ll250-35985
+ 62714 = 379,9,
The chords being £he greater, the
depth (3 3 J') is too small for theoretical
economy ; but it would hardly be prudent
to increase it.
131. If however we take the pier
towers at 27000, the right member equals
57096, which nearly equals Wc.
132. The Fink truss is better adapted
for a deck than a through bridge, and
possesses one advantage for either form
over all others ; " compensation " under
live loads or changes of temperature ;
each isosceles triangle or "element"
being independent in its action of every
other, there can be no loose counters
causing distortion of the bridge as in
some beam trusses. Its action in pract-
ice is said to be £i perfect." It would
seem that an increase of diameter of the
heavy chord of the Fink would benefit
it more than a similar operation would
benefit the quadrangular trusses. A re-
estimate can alone determine.
132. It may be remarked that the
number of panels in a Fink is, from the
peculiar design, some power of 2 ; 2, 4,
8, 16, 32, &c, thus fixing a panel's length.
The Quadrangular trusses on the contra-
ry can have any number of panels, thus
giving it a greater adaptability to
various spans. The Triangular truss
with suspenders has necessarily an even
number of panels. But with some of
the center panels built on the quadran-
gular plan (as has been done), thus giving
short posts, where material is most likely
to be wasted, the adaptability to any
span can be made equal to that of the
quadrangular trusses.
For very long and deep spans — 300 to
600 feet and upwards — vertical posts
throughout would seem to be desirable;
for if inclined, the flexure from their
own weight would be appreciable and
might continually increase besides.
The posts, when the truss is high
enough to admit of it, are often braced
together between their ends, thus shorten-
ing practically their length as compared
with their diameters, and adding materi-
ally to the stiffness of the system.
133. Bow String Girder. — This truss,
depicted in Fig. 15, is assumed, as be-
fore, to have 200 feet span, divided into
12 panels, and to weigh 336000 lbs. (en-
tire bridge). The center height is as-
sumed at 30 feet. The counters are
omitted in Fig. 15, as we shall assume
them out of action when the bridge is
loaded uniformly, which case will first be
investigated.
134. Using Bow's ("Economics of
MAXIMUM STRESSES TN FRAMED BRIDGES.
297
Construction," &c), notation, we denote
any bridge member, in Fig. 15, (1) by
the two letters placed either side of it;
thus the first vertical on the left is ab,
the next cd, &c. Similarly the first bow
piece on the left is aM, the next cM, &c. ;
the first chord piece is aA, the next bB,
&c. The same notation applies to the
forces AM, AB, BC, &c.
135. Let the bridge be loaded with its
own weight only, 14000 lbs. per panel on
one truss ; i.e., AB = BC = CD = &c.=
14000 lbs. Then the reactions AM and
LM are 5£x 14000.
Lay off, in Fig. 15 (2) the forces AB,
BC, &o. vertically, also the reaction
AM, and draw the lines, as per figure,
whose extremities are marked by any
two letters, x>arallel to the members of
the truss, Fig. 15 (1), indicated by the
same letters; then will the lengths of the
lines in (2), measured to the same scale
as the forces AB, .... give the strains
on the members of the truss (l) indi-
cated by the same letters.
Thus Ma, (2), is drawn parallel to Ma,
(1), and Ma, (2), measured to scale is the
strain on Ma (1).
Similarly Aa, ab, be, Mc, &c, in (2)
are the strains on the corresponding parts
in (1).
136. This results from the well-known
law of mechanics, that if a number of
forces acting at a point are in equili-
brium, then if we lay off the forces in
order, " the polygon should close." Also,
having given, at any apex, the direction
of one force, by following around the
corresponding polygon we find the direc-
tions of the others. If the force, repre-
senting the stress on a member, is thus
found to act away from the apex., the
member is in tension, if towards the apex
the member is in compression.
Thus at apex AMa, AM is given
acting upwards : then in (2) following
around the polygon AMaA in order, Ma
is found to act towards, and aA from the
apex; i.e., aM, (1), is in compression and
aA, (1) in tension.
Be careful to note now that these same
pieces act in an opposite direction at
their other ends. Thus at apex ABab
(1), aA acts to the left, being i?i tension;
then following around the corresponding
force polygon (2) in the order Aa#BA,
we find ab and bB acting away from the
apex, hence in tension. Next at apex
Mabc (l),aMcba (2) gives CM compres-
sion and be tension. Similarly all the
web members will be found in tension,
the bow in compression and the chord in
tension.
We determine first the strains at a
chord apex, to find the strain on the
vertical, then go to the bow apex above
it, where, the strains in two pieces only
being unknown, can be readily found.
137. The strains were of course
determined from a larger drawing, the
truss being drawn to a scale of 10 feet=
1 inch, and the force diagram being
drawn to a scale of 20000 lbs. = l inch.
We thus find that the dead load alone
strains the ties, be, de, fg, hi, jk, 4700,
4000, 3300, 2900 and 1300 pounds re-
spectively. The verticals thus carry the
greater part of the weights. With
engine at the foot of tie ab, its maximum
strain i,s 45000 lbs.
It was not considered judicious to pro-
portion the verticals (when acting as
ties) for a less strain, as a very slight
error in the length of a diagonal could
cause the vertical (neglecting the counter,
supposed loose however) to sustain the
whole panel reaction of 45000 lbs.
138. For a uniform live load, the
force diagram is similar to (2), and the
bow and chord strains can be most con-
veniently obtained from it. With the
locomotive excess placed so as to give
298
VAN nostrand's engineering magazine.
max. chord strains, a new diagram would
be required for every new position of the
load however and on that account it is
simplest to use the principle of moments.
139. The maximum moment about an
apex n panels distant from the abut-
ment is given by the eq., art. 39, by sim-
ply dividing by A, as is sufficiently evi-
dent.
Mn
\>
■n)
In the case of the Bow String gird-
er, the lever arms for panels Act, Cd,
Df, E/?,, F; respectively are ab, cd, ef,
gh and ij respectively. The lever arms
for the arch panels Ma, Mc, Me, M^ . . .
are the perpendiculars drawn from the
apices Ab, Bd, Cf, .... respectively
to the chords of the arcs Ma, Mc . . . .
Substituting now in the last eq.,
N=12, l=*£9 E=60000,— =1|, P = 30666
we have,
Mn =[255550(12-^) + 83333(10^ -»]ra
whence we find the strains in,
Aa=B£=
M, 3602713
Ma —
9.8
=427000
= 367620,
Mx
8.43
6527660
;377320,
17 3 17.3
&c, &c, as entered in the table below.
140. Maximum Web Strains. The
following method of ascertaining the
max. web strains is due to Stoney
(" Strains in Girders," etc., art. 211).
Suppose the truss without weight. Let
the live load, engines in front, extend to
the foot of the tie whose max. strain is
required. Then, in Fig. 16, if we sup-
pose the panel IJ ij cut and forces ap-
plied at the cut pieces equal and opposite
Fin. 10.
to the resistances of those pieces the
right segment of the truss will be held in
equilibrium by the reaction at the right
abutment, the horizontal tension in IJ,
and the resultant of the strains in 1/ and
ij. The two former met at M, hence the
resultant at j must pass through M.
Therefore, if we draw, by scale, ji
vertically, and equal to the reaction
(which is also the shear over panel IJ),
and draw 12 horizontally till it meets
jM produced at 2, then 2/ is equal and
opposed to the forces supposed applied
in the directions, ij and jl at j ; whence
drawing 24 parallel to ij, /4=strain on
tie, and 24 on bow ij for this position of
the load.
Similarly if we suppose the truss sev-
ered through IJjk, 2j will be the result-
ant of the resistances of jJ and jk at j,
or, j2 acting in the direction from/ to 2
is in equilibrium with those resistances.
Hence, drawing 23 parallel tojk, on fol-
lowing around the force polygon in the
order, /23/, we find 3/= strain on /J com-
pression as it acts towards j.
141. From this method of construction
we see that the strains on any two web
members as Ij and /J are greater the
greater the reaction, provided there is no
load on the right segment; hence, omit-
ting the case of the right segment being
loaded for the present, the strains on a
tie and the vertical connecting with its
top, when the greater segment only is
loaded are a maximum, when the live
load — engines in front — extends from
the farthest abutment to the foot of the
tie. The counters Ji and K/ are sup-
posed loose or out of action, hence were
disregarded.
141. We proceed similarly for the
other diagonals and verticals. The
method is the same for the counters Yg,
Yf, . . . . : the live load extending from
their feet to the nearest abutment for
their max. strains. Now add, with its
proper sign (+ for compression, — for
MAXIMUM STRESSES IN FRAMED BRIDGES.
299
tension), the effect on the posts of the
dead load, as found from the construc-
tion Fig. 15, to the strains just found,
from Fig. 1(5, when the live load extends
to the farthest abutment.
Post
Fig. 16
K/fc
Rh
Og
Dead Load.
11800
11000
11200
11900
11600
Live Load.
+
13000
+
22000
+
27500 -
+
31000
+
32300
Total Strain.
+ 1200
+ 11000
-f 16300
+ 19100
+ 20700
Next, in Fig. 15 (1), conceive the
diagonals only in the direction of the
counters — they thus suffer compression
for a uniform load — and draw the cor-
responding strain diagram due to dead
load only. It is convenient to draw it
directly over Fig. 15 (2), as the inclina-
tions of all the pieces (but the diagonals),
and also the loads, have been already
laid off in proper position. An explana-
tion of the construction for one panel
will suffice. Place b and c, Fig. 15 (1)
on either side of the diagonal from Ab to
ce, so that the bow piece is Mb and the
chord piece Be. Then in Fig. 15 (2) ex-
tend ab to intersection with Mc, and draw
cb || cb (1) to intersection with B& pro-
longed; then ab= — 18300 gives the strain
in the first vertical due to dead load.
Similarly we .proceed for other panels.
The strain diagram for Fig. 20, inverted,
applies here exactly. The strains in the
counters due to dead load are obtained
from the same figure.
Since, when the live load extends to
the nearest abutment the counter connect-
ing with the post is alone in action,
we must add the strains on the posts
found from Fig. 16, for this case, to the
strains just found on the diagonals in the
direction of the counters, due to dead
load. We thus find,
Posts
Fig. 16
KA
J?
K
Rh
^9
Dead Load.
17800
17000
16400
15300
14000
Live Load.
Total Strain.
-f 16500
-f 23000
+ 27500
+ 31000
+ 32300
- 1300
+ 6000
+ 11100
+ 15700
+ 18300
On comparing this table with the pre-
ceding, we see that, in this example, the
posts are most strained when the live
load extends from the farthest abutment
to the foot of the tie connecting with
them. The same is true for the main
ties, since they can only take tension.
The max. strains thus far found are
entered in the following table :
142. We have previously found that
for dead load the diagonal web members
are only slightly strained. If the count-
ers are tightened too much, it would
tend to relieve the main ties of strain,
but to increase the strains on the posts.
Thus if counter j"K is in action, say it is
strained 10000 lbs., then j 2 acting from
j towards 2 is opposed to the the result-
ant of the resistances J/, JK and jk.
Hence extend 23 so that 3 will have such
a position that a line drawn from it
parallel to counter /K to intersection, 5,
with jj will measure 10000 lbs. The
force polygon formed, _/235y, gives as
explained before, 23, compression on jk
(greater than before), 35, tension on
counter (10000 lbs.) and 5/ compression '
on post J/, considerably greater than
before.
Hence an ignorant tightening of the
counters may easily double or treble the
strain on the posts for which they will be
designed in what follows.
Another very objectionable feature in
this truss, is the fact that for a uniform
load there is tension only in the verticals,
whereas, when the train is only partially
on the bridge, they are each in turn sub-
jected to compression ; changing thus
quickly from a possible 45000 lbs. tension
to a max. compression of 20000 lbs.
(about, for middle posts), or the reverse.
The verticals were consequently design-
ed, each to consist of two plates connect-
ed by the usual latticing and angle irons
of sufficient section to resist both strains,
and were of course " hinged at both ends."
143. We thus see that the great
saving in the web in this form of truss is
really the greatest objection to it, at
least for a railway bridge. The bow
form is best used in the plate girder.
144. The successive reactions at the
right abutment in last Fig. are easily
found from eq. (5), art. 19, by making
the dead load, ^>=o. The reactions are
the same then as the shears on the right
segment. Expressing them in hundred
weight, we have
300
VAU nostrand7s engineering magazine.
Sx = 1391,
S2=1188,
S3 = 100(),
S4= 825,
S5=664,
S6=516,
S7-«83,
S =264,
158
92
39
0
moving off the bridge by modifying the
formula as suggested in art. 19.
145. Combining the max. strains
found on the main ties due to live load
with those previously given due to dead
load (art. 137) the results are entered.
Due regard was paid to the rear engine
Bow String Girder — Through Bridge.
Piece.
Kb
be
cd
de
ef
fff
*PostK&
Ji
K
m
% -.
Latticing, angles, &
Lower Chord
Tie Kl
U
v
m
Gh
Counter ¥g
w
Be
Cd
Be
Vertical Ties
17.7
16.
334
c. 27 lbs.pr.ft.
th.
n
Strain.
427000
413140
404370
396330
388780
381660
1200
11000
16300
19100
20700
2263400
34200
41000
46000
49900
51300
50200
48000
43200
43100
44200
. 45000
.39
,39
0
0
0
0
0
0
0
0
0
0
.13
8000
9040
3000
10420
7500
8470
Area.
53.4
45.7
44.7
43.8
43.
42.2
0.
3.7
5.4
6.9
6.9
217.2
4.6
5.5
6.1
6.6
6.8
6.7
6.4
5.8
5.8
5.9
5.3
Len'th
19.6
18.3
17.5
17.1
16.8
16.7
17.3
23.
26.9
29.2
30.
111.4
19.3
24.
28.5
31.8
33.7
34.3
33.7
31.8
28.5
24.2
121.2
No.
Weight.
lbs.
13955
11151
10430
9986
9632
9396
0
1135
1937
2492
1380
12032
48267
1184
1760
2318
2798
3055
3064
2876
2459
2204
1903
8565
Totals.
64550
6944
12032
48267
32186
* The thickness of metal
acting as a strut.
th " is made up of that due to the vertical acting as a tie (5.3) + that due to its
together with the strains on the other
members of the bridge in the adjoin-
ing table ; from which we deduce as
before the
Bill of Materials.
Bow String Through Bridge, 200' span, 30' rise.
lbs.
Bow and posts, with latticing &c. . 83526
20 p. c 16705
Chord ties and counters 80453
15 p. c 12068
Other items as in art. 47 134100
Total weight of bridge.
Assumed weight. . . .
.326852
.336000
9148
146. We have assumed the same per-
centages and estimates of loops, trans-
verse bracing &c, as previously given
for the Triangular and Whipple bridges,
which is only approximately correct.
The bow piece can be more convenient-
ly constructed of some other form than
the phoenix column, so that the above
estimate is favorable to this form of
truss. The principal objection urged to
the Bow String Girder is, that the web
members are so slightly strained from
dead load, that the rolling load may
find them out of action, thus giving rise
to hurtful vibrations.
The difficulty in cross-bracing the bow
is also a great objection to this truss as
a through bridge.
147. In the previous investigation of
the Bow String Girder, only one system
of triangulation was assumed and the
MAXIMUM STRESSES IN FRAMED BRIDGES.
301
most economical height was not found
as for the other trusses examined.
As the web is comparatively light and
some of the ties have about their most
economical inclination, 45°, it is not
probable that a double system of triang-
ulation, for the span and panel length
assumed, would involve as much saving
as we found in the quadrangular truss.
The height assumed, 30 feet, is slight-
ly greater than for the beam trusses, as
it was thought that the light web would
admit of a greater height. Trial only
can determine the most economical
height. It would seem that the change
of a foot or so would effect a very slight
saving however, if we may judge at all
from the previous investigations concern-
ing the beam trusses.
148. Analytical Formulce.
Cj__ — -
Cs---
— -zi<y
\
Cl
*v,
/
X-
\d
V
C\/
^1
l \
Fig. 17
Let us call the successive lengths of
the bow, cl9 ?„,... ; the length of a post
y, the length of the post to left of it yx ;
d the length of a diagonal connecting y
and yx\ Ay, --difference between yx and
the length of the post to the left of it ;
Ay=y— yr Also the pieces can be des-
ignated by the letters next them on
the figure above, prefixing the words
post, tie or piece to avoid any confusion.
Call the moment of the external forces
(reactions and loads) on one side of post
y, about its foot as a center of moments,
My ; similarly for Myi ; also call the shear
in the panel included by y and yl9 for
the same distribution of the load Sy.
Designate a panel length by I ; the
inclinations of pieces cv c2, . . . by al9 a„
. . . and of the diagonal d by fi.
Also denote the strains in c3, y, d, etc.,
by the corresponding capital letters, C3,
Y and D.
149. Suppose a vertical section cutting
pieces c3 d and I, and take the intersec-
tion of d and I as a center of moments to
find the strain C,
thus,
M, =Cay
y cos «3
I
C,
whose
I
r —
M^
y
lever arm is
a)
If we supply forces (as in art. 7, Fig. 2)
at the supposed vertical section (cutting
c3 d and I) equal and directly opposed to
the resistances of the cut pieces, we must
have the algebraic sum of their vertical
components equal to Sv. Compare art.
8. Now since the bow is always in com-
pression— since every weight on the
truss causes an upward moment — the ex-
ternal force opposed to the resistance in
piece C3 acts downwards.
S„ =D sin. fi + C sin. a
»it+
M,
V I
y, v y if
Ay
(2)
On the right half of the truss the force
opposed to C acts upwards. Since Ay
is then minus eq. (2) applies on changing
the sign of Ay. Again, note that
when Sv is minus it must be so substi-
tuted in eq. (2). When D is plus, the
diagonal is in tension, otherwise in com-
pression.
The reader will do well to sketch the
truss up to the section and the forces act-
ing on it, as in Fig. 2, in this and subse-
quent articles.
150. Next conceive the section parallel
to diagonal d, cutting pieces c2 y2 and I ;
and balance the vertical components of
the "acting forces," which include the
reaction and loads left of the section,
and the supposed forces equal and op-
posed to the resistances of the cut
pieces
Sy = Y1-\-C,2 sin. a2
From eq. (1) we can derive,
Myi c^ AjA =
c„
C„ sin. a =
2/,
I
Ay,
NowMy,=My— S„ £, as may be shown as
follows :
Suppose a section cutting y, c3 and the
chord piece to right of piece I; and sup-
ply forces equal and opposed to the re-
sistances of the cut pieces. Decompose
the applied force =Ca, at top of post y,
into vertical and horizontal components.
The latter component is equal to the
force applied at the cut chord piece and
forms with it a left-handed couple, equal
to My, since the moment of the vertical
component +Y=SW is zero; these forces
302
VAN NOSTRAND'S ENGINEERING MAGAZINE.
acting through the center of moments —
the foot of post y.
Hence, regarding the left-handed
couple (=My) and the sum of the verti-
cal components ( — Sy), acting down-
wards if Sy is + , as the external forces
at the section, we have the moment
about the foot of post yl9 M-yi=My— Syl
as was to be proved.
It is useful to note that, since My =
Myi + Sy I, the moment increases in going
from y1 to y, so long as Sy is positive.
Therefore at the point where Sy — 0 the
moment is a maximum (compare art. 90).
Substituting the above value for My x,
we have for the strain in the post y1
Y=S,
M,
"Sy I
y*
Ay,
I
(3)
As before, when Sy or A y, are nega-
tive, they must be so substituted in this
formula.
151. The Maximum Strains on a tie
we have previously found to be when the
load extends from the foot of the tie to
the farthest abutment; for a counter tie,
the load extends from its foot to the
nearest abutment. Therefore, for maxi-
mum strains, the shears S,, are easily ob-
tained from eq. (5), art. 19.
The corresponding moments My are
found thus : to Sy add the dead load be-
tween the post marked y and the left
abutment to find the reaction, whose
moment about y, minus the moment of
the downward loads from the abutment
to y gives M^.
152. Example. Required the max.
strain, D the counter ij ever sustains,
for the bow string girder, Fig. 16 pre-
viously examined. The live load ex-
tends from M to J. By table, art. 21,
S=-191?2. Reaction at A=- 19172 +
8X14000 = 92828.
.♦. M,, = 92828 + 150-112000x75 =
5,524,200,
whence by eq. (2)
D
31.8
.9\
19172 +
5524200.3.9x6
26.9 \ ' 23 100 /
43770.
The graphical analysis gave 43200.
153. For a post as Ee, the live load
must either extend from M to F or from
A to D to cause max. strains. In the
first case the strain on Ee is by eq. 3.
Y = 87364-
9613667-87364^
26.9
3.9x6
" 100
16402
Secondly, since post \i for live load from
M to J sustains the same strain as Ee,
when the load extends from A to D, we
have for the strain in this case,
5524200 + 19172^
Y
19172 +
26.9
2.3X6
100
10808
The graphical analysis gave 16,300
and 11,100 respectively. In this way
we can form the following table ; where
column 1 gives the post, columns 2 and 3
the strains sustained by it, when the live
load extends from the foot of the tie or
counter connecting with it to the farthest
or nearest abutments respectively:
Cc
1600 comp'n
182 tension
Dd
9318
6200 comp'n
Ed
16402
10808
W
19008
17150
Gg
18470
18470
In this case, we see that the posts are
most strained when the live load extends
to the farthest abutment. The strains
found by the preceding formulae were
found to differ from those found by
construction less than 1000 lbs. as a
mean, the extreme difference being 3000
lbs. This is due partly to the short
lengths of the bridge members from
which their inclinations were derived,
and partly from the unavoidable errors of
construction, as well as from the dimen-
sions being taken to only tenths of a foot
in the formulae. Other formulae could
be given but we have preferred those of
Schwedler on account of their compact-
ness and as introductory to his bridge.
154. The Schwedler Bridge. — In this
bridge, the upper chord is parallel to the
lower chord in those panels where count-
ers would be required in a Pratt or a
Howe truss ; e.g., for the four middle
panels, for the span, panel length and
loads previously considered. In the
other panels, the height of post is so reg-
ulated that no counters are required; ie.t
the diagonals act as ties only or as struts
only.
MAXIMUM STRESSES IN FRAMED BRIDGES.
303
Now the max. reverse strain, in a
diagonal as T>c (Fig. 18), is when the
£ront engine is at C and the load extends
to A. The condition for this truss is,
that this strain must be zero for those
panels where no counters are to be used.
Placing eg. (2) equal to zero, we deduce,
for the left half of the truss,
Ay=y
SyJ
Ml
(4)
In this formula, it is understood that
the front engine is at the post marked yl9
and the live load extends to the left
abutment, the moment My being taken
about the post y.
155. Example. — Take the span='200,
Z =11-0-0, loads &c. as before. Assume
Y.e—m'—y.
With engine at D and load extending
to A, the moment about E is
My=5,844,000
Sy=-19l72
,.A3,=-3o19mx1**
1.6
5844000
.*. D<£=30— 1.6=28.4 feet.
Again, write y=28.4, with load from
A to C,My =4,525,000 and Sy= -39836,
whence by (4) Ay=— 4.1 .*. Cc=24.3
finally put y=24.3, S= -59112, with
live load at B only, the moment about
C=My=2,981,000 .'. A y— — 8, whence
B6=24.3-8 = 16.3.
156. Should more concentrated loads
ever be allowed to pass over the bridge,
the posts should be increased in length
for them, otherwise the destruction of
the bridge is inevitable. It should
therefore be proportioned for a greater
load than can ever by any possibility
come on it, which would somewhat lessen
the economy shown below.
157. The max. strains on ties and
posts are found by using eqs. (2) and (3)
as previously explained, the load extend-
ing to the farthest abutment for the
posts.
The minimum strain on the first and
last three diagonals is zero, for this
truss; the same is true for the posts at
their feet, since the vertical strain is
transmitted to one by the other entirely.
158. The computation of some of the
web members will now be given.
Max. strain in bC is when engine is at
C and load extends to M. In eq (2)
write d=bc=23.3, y, = B6=16.3, y=Cc
= 24.3, Ay =8 &c, whence max. strain in
,,0-^.3, 6294667_8_
iC-i6T3(18184° — -zU~H*} ~82'131
Ay, A 2/j become zero for some of the
center panels, reducing the case to that
of the Pratt truss.
From eq. 3 the max. strain in post Cc,
(load from M to D) is,
8,148,000-1489601$* 8X6
14 ~M3 100
= 37060.
159. The chord strains are determined
as explained for the Bow String. The
lever arms of C2, C3, C4, as determined
from a drawing, are 21.9, 27.6, 29.9
respectively.
160. The results for the Schwedler
truss of 200' span 30' center height, &c,
are entered in the following table:
(See Table on following page.)
Bill of Materials.
Schwedler Bridge, (through) 200' span 30' high.
lbs.
U. chord and posts 78,574
20 p. c • 15,714
Ties and lower chord 65,801
15 p. c 9,870
Other items as in art. 47 134,100
Total weight of bridge. . . 304,059
Assumed weight 336,000
31,941
161. Collecting together the estimates
of weights of the through bridges exam-
ined, arts., 108, 128, 145 and 160, we
have, in round numbers,
Weight of Triangular Truss, 325000 lbs.
" " Whipple " 325000 "
" " Pratt " 333000 "
" " Fink " 356000 "
" " Bow String " 327000 "
" " Schwedler " 304000 "
The pier towers of the Fink were put at
27000 lbs. These weights will differ
still more on a re-estimate, on assuming
dead loads more in accordance with the
truth.
4
304
VAN NOSTKAND7 S ENGINEERING MAGAZINE.
SCHWEDLER THROUGH BRIDGE TABLE OF WEIGHTS.
Piece.
*Bow Cj...
C8...
8::::
c5...
o....
*Post Cc...
T>d...
Be...
F/...
%...
Tie Bb
Cb
Dc
Ed
Fe
Of
Counter Hg.
Vi.
Chord AC.
CD..
DE..
EF..
FG..
12
12
9
30
th
Strain.
e.
b.
308910
.39
7650
298060
it
9040
317930
"
"
345960
"
(<
374530
"■
"
381660
< i
<<
37060
0
3930
54466
0
"
61260
0
"
58648
0
"
31320
0
2810
45000
.13
8470
82131
0
7500
94830
0
<<
101860
0
"
99886
0
"
67054
0
"
35809
0
"
6151
0
"
221020
.39
10420
268630
"
"
308970
< t
< i
344808
1 1
"
374530
"
"
Area.
Length.
No.
k.
D"
'
40.4
23.3
4
iP_
32.9
18.5
• <
35.2
17.2
"
38.3
16.7
"
41.4
100
<«
42.2
K
< i
9.4
24.3
< <
13.8
28.4
"
15.6
30
< <
15.
30
« 4
11.1
30
2
"
5.3
16.3
4
i e
11.
23.3
"
"
12.6
29.4
"
el
13.6
32.9
(<
< e
13.3
34.3
"
((
8.9
(<
"
t <
4.8
"
(<
2.
"
"
a
21.2
100
100
<(
a
25.8
"
"
29.6
"
it
33.1
((
"
< t
35.9
((
"
' 1
Weight.
Totals.
lbs.
12551
8115
8072
8528
9200
9378
55844
3045
5225
6240
6000
2220
22730
1152
3417
4939
5965
6082
4070
2195
915
28735
9422
5733
6578
7355
7978
37066
* The compression members are regarded as Phoenix columns in the computation, though other forms
may be more convenient in construction. Ci was taken as "hinged at one end," the other chord panels as
" flat at both ends," the posts as " hinged at both ends."
The superiority of the Schwedler Truss
in point of weight is marked, and should
receive careful attention from construct-
ors.
162. Several other through trusses
were examined, as the Lenticular or Fish-
bellied Girder, and the Triangular, with
two suspenders to a panel, instead of one;
but little or no economy was found over
the Whipple Truss above. The truss
figured in Van Nostrand's Magazine,
for November, 1877, p. 461 (Fig. 8), on
data above, weighs 320,000 lbs.
163. Bow String Deck Bridge. —
Formulae. — Call the bow pieces tl9 12 . . . ;
the length of the post to the right of y,
?/2 ; put y2—y= Ay2 ; the other notation
as before.
is, T4
My t,
The strain in piece tA .
(5), since the lever arm of piece
tA about the top of post y=y - .
164. Now conceive a vertical section
cutting pieces I, d and £3, and balance
the vertical components.
Ay
d
.-. S,
D^+T,
D
+
My-SyJ.
.'. D:
Sy^+Sy^
y y
Ay
dM.
y$
A- 'iv
i ts
Ay
I
.,D=^(Sy-^4-2/) (6)
y\ y y I /
To the right of the center, Ay is
minus, whence the — sign in the( ) is
changed to 4- as is evidently correct.
165. Next conceive a section parallel
to piece d, cutting pieces /, y and t0 and
balance the vertical components of the
MAXIMUM STRESSES IN" FRAMED BRIDGES.
305
forces opposed to the resistances of the
cut pieces with Sy we find,
My Ay2 m
y i {)
The same formula applies to the right
of the center, since Ay2 is then minus
and the eq. becomes
:Sy-T4^Sy
Y=Sy + -=3L
y
My Ay5
, where Ay2=y-y2
When Sy is minus it must be so regard-
ed in the previous equations.
As the application of the formulae is
essentially as just explained for the
through bridge it is needless to give it.
166. As it was of special importance
to ascertain whether the posts were most
strained by the live load extending to
the farthest or nearest abutment from
the posts considered, for the loads &c. as
previously given, the following strains
were tabulated referring to the next
figure : #
Post.
Live Load from
Live Load from
Post to farthest abt.
Post to nearest abt.
ob
50718
60655
cd
57400
60584
ef
66060
62970
gh
70108
68450
V)
71564
71750
kl
73632
73632
from which we ascertain that in this case
ab and cd are most strained when the
live load extends to the nearest abut-
ment ; for the other posts it extends to
the farthest abutment.
1G7. In this deck truss the construct-
ive difficulty of the joints of the bow is
not experienced as the bow is not in
tension. The web is heavier and the
posts may be made of phoenix columns,
with square joints at their connections
with the chord. These vertical members
now bear but one kind of strain; alto-
gether the truss is a good one, and is
worthy of more consideration than it has
received, as it will be found to be the
most economical in weight of any of the
deck bridges examined.
168. Graphical Analysis — The next
figure gives the form of the truss, omit-
ting the counter ties, and the strain
diagram for the uniform dead load of
14000 lbs. per panel; which, using Bow's
Vol. XIX.— No. 4—20
admirable notation, needs no further
explanation. From the strain diagram
we find the dead load strains on ties, be,
de, fg, hi, Jk, respectively, to be, in
round numbers, 6000, 5000, 4000, 3000
and 2000 lbs; the strains on the posts
vary from 18000 on ab to 14000 lbs. on kl.
169. If the members of the bow in any bow
string truss are given such inclinations that the
strains on the web ties are zero, i. e. that in the
strain diagram b and c coincide, as well as d
and e, f and g &c. , then the apices of the bow
are points in a parabola. For in the strain
diagram the points a, b, c, d, e, . . . . will all lie
in the vertical through a, and then since ab=
bd=dg . . . . , the difference between the tangents
of the inclinations to the horizontal of any two
consecutive bow pieces is the same. For re-
garding momentarily Aa as unity, ab=bd=dg
= .... is the tangent difference in question.
This is a property of the parabola Thus
assume its emation y2=mx ; give x the incre-
ment h and call the corresponding increment of
y, k .-. (yx k)2 =m (x x h). Whence, expanding
and taking the difference between the two
equations, 2 yk-\-k2 = mh
hh = ±(2y+k)
k m
h
Now -= tangent of the angle made by a
h
chord of the parabola with the axis of y. (In
the figure of the truss a horizontal drawn
through the point MJm (the origin) may be
taken as the axis of Y, the line kl as the axis of
X).
Now giving to y the successive values o, k, 2k,
'3k .... we find for - the successive values,
k
- k, 1 Sk, - 5k, -7k,....
m m m m
whose difference is — 2k, a constant,
m
which
was to be demonstrated.
In the figure of the truss k may be regarded
as equal to a panel length 16| feet, whence h
will be the vertical distance between the
extremities of the bow piece, the tangent of
whose inclination to the horizontal is given by
the value of—, corresponding to the value of y
for the lower end of the bow member.
When a parabolic bow string is loaded uni-
formly the strain throughout the string is
uniform, since, in the strain diagram a, b, c, d
. . . are in the same vertical.
170. As before, to find the max. strains
due to live load only on tie 14, we sup-
pose the front engine at IJ and the train
extending to the farthest abutment. Lay
off the reaction at LM from 1 to 2, and
draw 23 parallel to chord to intersection
with 13 passing through LM. Then 13
— resultant of reaction and strain in
chord panel J, must be in equilibrium
306
VAN nostrand's engineering magazine.
Y-"
A N
K
c
D .. E ,.F\, G ,
.H,, I ^, J
r&./t. ,
|X
\ c
\ e
\ (J
v
V
7
/
5 /
A
-y
/I
d\
A
E\
\
/m
7
l
*6
with strains in tie 14 and 16; hence
drawing 34 parallel to 16, 14=strain on
tie due to live load.
Similarly, drawing 35 parallel to 17,
15= strain on post 15 due to this position
of the load ; but we shall find that the
posts are most strained from the live load
alone when it extends from the nearest
abutment to the post considered; which
strains as well as the strains on the
counters are determined in a similar
manner to the above. Now add the post
strains due to live load — extending to
farthest abutment — to dead load strains
obtained from diagram above, and com-
pare these totals with those found, by-
adding the post strains due to live load
— extending from post to nearest abut-
ment to those found (from a diagram
similar to Fig. 15 (1) and (2) inverted),
due to dead load, from a figure where
diagonals in the direction of counters are
alone represented.
We reach the conclusion of art., 1 60.
From the last mentioned diagram, the
dead load strains on counters are found.
171. The total strain on any post can-
not be less than 45000 lbs., (the panel re-
action), when the engine is directly over
it; and proceeding as above we find that
the strain on the posts due to live and
dead load is not in any case less than
45000 lbs.
Suppose that the loads are so placed
that AB has, say, double its value given
in the figure, the reaction MA remaining
the same; then in the strain diagram for
aB, ba AQc'b (c' being in the prolonga-
tion of be at its intersection with Ce) we
see that be must now act as a strut;
otherwise ab takes the whole load (2 AB)
and a counter must be introduced from
its foot to cC.
It follows that, for the assumed truss,
the counters next an engine may be in
action when the whole bridge is loaded.
172. The maximum chord strains are,
for panels Aa, Be, Ce, .... respectively,
-gjg > jyfjj 23 ; the ^^ armS be"
ing respectively ab, cd, ef, . . . .
For the Bow we ascertain the lever
arms as follows: conceive the panel as
Mdec cut, take the intersection of the
tie and upper chord panel cC as a center
of moments, and from it draw a per-
pendicular to Md produced, which is
thus the lever arm of the strain in Md.
In this case M2 divided by this lever arm
is the strain in Md, M2 being the maxi-
mum moment when cC is taken as the
center of moments.
The max. moment for both Ma and
Mb is Mj hence M2 divided by the
length of perpendiculars from «B to Ma
and Mb respectively give the strains in
Ma and Mb respectively.
Similarly for other divisions of the
bow.
173. The strains are entered in the
following table. For the posts, 6 was
taken at .25 as an average, from which
none of them differ much. For the ties
MAXIMUM STEESSES IN FRAMED BEIDGES.
307
Bow String Girder — Deck Truss.
Piece.
Chord, cv
Post ab.
cd.
ef.
gh.
ti-
ki.
Tie be.
hi
jk
Counter 1.
2.
3.
4.
5.
d.
I
d
th.
Strain.
„
//
13J
15
1*
367620
1909820
8
c t
__5_
59000
8
26
7
60800
10
27.6
A
66000
10||
30.
7
T6
71400
lit
30.
t
73900
12
30.
f
73600
426860
407550
400470
395270
390350
387440
45000
50000
52000
54000
54000
49500
45200
39800
37000
" 35300
0. fc
39 9050
" 9270
j
25 8140
" 5950
" 5»30
" 5290
" 5290
" 5290
39 10420
7500
Area.
40.6
206.
7.2
10.2
11.3
13.5
14.
14.
41.
39.1
38.4
37.9
37.4
37.1
6.
6.7
6.9
7.2
7.2
Length,
17.3
23.
26.9
29.2
30.
19 6
18. 3
17.5
17.1
16.8
16.7
24.2
28.5
31.8
33.7
34.3
33.7
31 8
28.5
24.
19.3
No.
k.
Weight
9022
45778
941
2353
3466
4842
5451
2800
10715
9543
8960
8641
8377
8258
1936
2546
2925
3235
3293
2966
2544
2013
1568
1209
Totals.
54800
19853
54494
24235
6 is put at o. The maximum chord
strains are Aa=367620, Bc=377320,
Ce=381510, %=384540, E»=384?90,
F£=381660; the sum of the last five be-
ing 1,909,820, as entered in the table.
The total weight found is the same
whether these chord panels are consider-
ed separately or collectively, the length
being the same for each piece.
Bill of Materials.
Bow String Deck Truss, 200' span, 30'
center depth.
lbs.
U. chord 54800
Posts 19853
20 p. c. on two last 14930
Bow 54494
Ties 24235
15 p. c. on two last 11809
Other items (art. 91) 127230
Total weight. 307851
Assumed weight 336000
28,649
174. The Triangular, Fig. 7 as a Deck
Truss, can be best compared with the
Whipple, etc., with vertical end posts.
However, let us assume the abutments
built up to grade to compare with the
deck trusses examined. The max. strains
are identical with those for the through
bridge, except that the vertical posts
must now sustain a max. load of about
45000 lbs. The suspenders may be made
of one square inch cross section. Esti-
mating as usual we find its weight as
given below :
175. . Comparison of Deck Bridges of
200' span, loads, etc., as previously
given.
Triangular, 28' high, 321,000 lbs.
Whipple, " " 326,000 "
Fink, 33§ " 317,000 "
Bow String, 30 " 307,000 '<
The Schwedler as a Deck Truss would
doubtless prove lighter than any of the
previous trusses.
176. With other details than those as*-
sumed — and our best bridge companies
have devised some excellent ones — the re-
sults found may be slightly varied; but
it is believed that the general compari-
sons are correct for any given details.
At any rate the data is all given so that
308
VAN NOSTKAND'S ENGINEERING MAGAZINE.
errors can be detected or modifications
of design readily made.
177. Although the loads previously
assumed are for railroad bridges, yet the
formulae, or methods given, can be
easily adapted to highway bridges,
where the live load is usually taken as so
much per square foot of roadway, vary-
ing from 35 to 100 lbs. per square foot.
178. A matter of great interest to en-
gineers is the determination of good
formulae for compression members.
Government aid is anxiously looked for
in this direction to institute the proper
experiments. Various formulae for dif-
ferent cross* sections are being introduced
in some specifications, though they are
founded on comparatively few experi-
ments, and thus are only provisional, as
indeed are the formulae previously used
in this paper for unit strains; but the
deduction of Wohler that a piece will
bear a smaller maximum strain the
greater the extremes of strain to which
it is subjected is not provisional, but a
fixed fact, which must be regarded if a
bridge is to be designed scientifically;
and it is to be hoped that the above will
show that there is no difficulty in the ap-
plication of Launhardt's formula founded
on this law.
179. It is believed that there will be
no difficulty in applying the preceding
principles to any form of truss in ascer-
taining the greatest or least strain that
any member is ever called on to bear.
If the truss is composed of two or more
web systems, not connected at their in-
tersections, estimate the influence of each
separately and combine the effects for a
piece that is common to the two or more
systems. All the principles relating to
the method of ascertaining max. and
min. strains, etc., that pertain to a sim-
ple system apply to each web system in
turn.
UNIFORMITY IN- SANITARY ENGINEERING.
From "The Engineer."
We admit that there are exceptions to
every rule, and that it is impossible to
lay down a hard and fast line, to be ad-
hered to undeviatingly in any branch of
the profession. Nevertheless the greater
the number of instances to which a gen-
eral rule can be made applicable, the less
troublesome, and what is infinitely more
important, the more certain becomes the
task of the engineer. By the phrase
" less troublesome " we do not mean to
imply that the work of an engineer, in a
sanitary or other point of view, is to be
devoid of trouble and anxiety, but sim-
ply that he is fairly entitled to be relieved
from any amount of trouble which is, in
reality, incurred merely for trouble's
sake. Under the latter category may
be included unnecessary, and frequently
useless routine work, and the planning
and execution of schemes which in some
cases are nothing better than crude ex-
periments, undertaken to meet contin-
gencies which might readily be provided
for by existing arrangements enforced
by a proper head or central administra-
tion. We are not now about to advocate
the creation of a chief or central sanitary
authority for large districts, although it
may be a matter for consideration wheth-
er the important object included in the
title of our present articles might not be
greatly promoted by the establishment
of such an authority.
It cannot fail to strike anyone who is
acquainted with the various drainage
and sewerage systems prevailing in
different towns, that some must possess
advantages over others, advantages
which are general, and not peculiar to
the town or district to which they per-
tain. It is just possible that there may
not be any two towns or districts placed
under precisely identical conditions of
either nature or art, but there are un-
doubtedly a large number which are
to all intents and purposes, practically
so located. To all these, therefore, one
and the same uniform system of drain-
age and sewerage might be applied
provided only that a selection could be
made of the system presenting the best
general advantages. Considerable lati-
tude must be allowed, and great discre-
UNIFORMITY IN SANITARY ENGINEERING.
309
tion used in determining such a selection.
Hitherto in some instances so-called
compulsory injunctions have been made,
and pretended fines imposed, when com-
pliance with the demands of the author-
ities was utterly impossible. The case of
Kingston-on-Thames, which occurred
some two years ago, was of this charac-
ter, in which the penalties incurred, for
non-compliance with the injunction grant-
ed to the Thames Board of Conserv-
ancy, amounted to the equally decisive
and preposterous sum of £10,000. It is
needless to add that the penalties were
never paid, but it is certainly not credit-
able to our sanitary legislation that such
penalty should either have been incurred
by the one party, or inflicted by the other.
The carelessness and indifference of the
former in incurring it is equalled only
by the folly and impotency of the latter
in inflicting it.
The statistics of large towns prove
that no one system for the disposal of
sewage can be rendered universally ap-
plicable; but they do not prove that the
same rule, of necessity, applies to the
collection and removal of it from human
habitations. With respect to the latter,
if we choose to beg the question, the
one universal system would be found in
that of water-carriage, which unques-
tionably conveys the sewage from the
vicinity of dwelling-places in the quick-
est, the cleanest, and in the manner the
least offensive to our English habits and
prejudices. It is worth noting that, at
the conference on the health and sewage
of towns held last year, it was one of the
" resolutions " arrived at, that, " for use
within the house no system has been
found in practice to take the place of
the water-closet." If this is the case, it
could tend very much to the desired
uniformity in sanitary engineering if
that system of collection and removal
were rendered compulsory in all instan-
ces where good cause could not be shown
against it. This would be the more
advantageous, ina=much as there is only
one method or plan upon which the wet
or water carriage system can be applied,
whereas there are several methods by
which the dry system can be brought
into operation. Of those different
methods it is not easy to determine
which is the best. It would appear
that recent experiments demonstrated
that of them all — and they are all more
or less offensive — the pail system is per-
haps the least objectionable, especially
in large towns. Upon whatever plan the
dry system may be carried out its effi-
cient working depends entirely upon the
way it is managed. It possesses none of
the automatic advantages of removal be-
longing to the water carriage principle.
The contents of privies, ashpits, middens,
cesspools, tubs and pails, must be re-
moved by manual labor and transported
to their destination along the streets and
public thoroughfares. The pneumatic
plan, which is adopted in some of the
! towns of Holland, is an exception to the
latter statements or, rather, it would be,
were it a genuine dry system. But the
pneumatic system deals with a certain
quantity of liquid as well as solid sew-
age. It is, moreover, both complicated
and expensive in construction and work-
ing arrangements, easily deranged and
put out of order, and troublesome and
difficult to repair. One of our first san-
itary engineers has remarked on this
plan that he did not "know one English
town in which the apparatus, if adopted,
would be other than a costly toy."
To return to the suggestion made
at the commencement of our article,
with relation to the establishment of
large central sanitary authorities or
boards, it is obvious that had such au-
thorities existed during the " precipitat-
ing mania," happily now over, it is not
too much to assert that enormous sums
of money would have been saved by
both willing victims and unwilling rate-
papers. It might be well asked, of what
use are Government Commissions, whose
labors are carried on at the expense of
the community, if the results they arrive
at are to be permitted to be totally ig-
nored, and processes which they unani-
mously and unequivocally condemn are
allowed to be put into practical opera-
tion, at the cost of those who, however
reluctant to pay, are powerless to pre-
vent the imposition of the tax. Assuming
that the centralization of sanitary admin-
istration were an advisable proceeding,
the first difficulty to be surmounted
would consist in the selection of a stand-
ard or unit of area over which any cen-
tral authority should have sole jurisdic-
tion. It is absolutely necessary that the
unit should be large, in order that some
310
VAN NOSTRAND'S ENGINEERING MAGAZINE.
uniformity at least should result from
the administration, and a termination be
put to the evils which attend the pres-
ent condition of affairs in which every
" sewer authority," no matter how small
may be the field of its operations, can
do what seems best in its own eyes.
Were the results of bad and defective
sanitary arrangements to be confined to
the particular district or locality in
which they originated, the matter might
be left in the hands of the sewer author-
ity of that district to be dealt with.
But this is frequently not the case. At
present, owing to the want of boards of
conservancy, rivers and streams which
are preserved from pollution along cer-
tain portions of their course, are not so
preserved in others. It is becoming every
day more and more apparent that we
shall be compelled to increase the
scale upon which the sanitary en-
gineering of the country is con-
ducted. The water supply— the most
important feature in the whole of
sanitary administration — of many of our
large towns is lamentably deficient in
both quantity and quality. The fact is
that the original sources of supply are no
longer adequate to meet the ever-increas-
ing demands made upon them. The
Thirlmere scheme as a new source for
the supply of water to Manchester is a
case in point. It may be remarked here
that there are comparatively few water-
closets in Manchester. They are discour-
aged as much as possible by the local
authorities, who practically restrict the
use of them to houses of the better class.
If Manchester had been drained and
sewered similarlv to London, on the
water carriage principle, it would have
required a better supply of water long
before the present time.
It has been proposed that the unit of
area referred to should comprise a coun-
ty, and we do not think this would be
found in any degree excessive. There
is a good deal to be said on both^sides
of the question, but there is no doubt
that the establishment of central or dis-
trict boards would tend to the reforma-
tion of our present sanitary legislation.
They would do away with a number of
inferior local boards and officials, pro-
fessional and otherwise of very limited
qualifications and attainments, \ and, in
their stead, substitute uniformity, efficien-
cy, and economy. There is one point
which deserves the serious consideration
of the present Local Government Board,
or any future head or central sanitary
authority. It is the position of the engi-
neer and surveyors to local boards. The
tenure of their office depends upon the
will, and frequently the caprice of their
respective boards. It ought ..to'be simi-
lar to that of the medical officer, who
has the right to appeal to the chief au-
thority in case of dismissal by the board.
A HISTORY OF DEEP BOEING, OR EARTH BORING, AS
PRACTISED ON THE CONTINENT.
By Me. J. CLARK JEFFERSON, A. R. S. M.
A Paper read before the Midland Institute of Mining Engineers.
The writer observed that in bringing
under the notice of the members of the
Institute a short history of deep boring,
or earth boring, which has been, and
was still, carried on on the Continent, he
believed he should be able to point out
many inventions and arrangements
which were quite new, and not unwor-
thy of the attention of most of the mem-
bers. The outcrop of the coal measures
in this country, the comparatively small
depth and level character of the coal
seams, has hitherto not made such great
claims on the art of boring as on the Con-
tinent, where lying mostly under newer
formations and at great inclinations,
necessitated deep borings previous to
the commencement of sinking operations.
Lately, however, in this country they
had witnessed the searching for coal
under formations newer than containing
the coal measures. The Wealden bor-
ings in Sussex were, perhaps, the most
notable examples. The fact of part of
A HISTOKY OF DEEP BORING ON THE CONTINENT.
311
the Nottingham coal-fields dipping east-
ward naturally led to the question
—whether there would not be some
probability of finding coal in the center
of Lincolnshire if borings were carried on
sufficiently deep. Indeed, the deeper
the coal seams lie, the greater will be
the need of careful boring to ascertain
their depth and character, and it might
be that at some future date it would be
the lot of some of the members of that
Institute to search in a more easterly
direction for fresh deposits to supply
the exhaustion of seams in the center of
the coal measures in West and South
Yorkshire. Although he should en-
deavour to deal with the subject as much
as possible in an historical manner, he
should consider it under the following
heads:
First, the borer or boring apparatus;
And Second, the surface arrange-
ments, and, lastly, the removal of the
hindrances occurring during boring,
including the lining of bore holes. The
first mention of the art of boring was
in a book published by Mr. C. T. Delius,
in Vienna in 17 70, in which they had
only the mere mention of earth-boring.
It was pretty generally stated that the
art of boring was invented by the
Chinese, and was introduced from China
into Europe by Jobard. Boring may be
carried on in two ways, either with the
use of rigid rods or with a rope. Until
the invention of the diamond rock drill,
boring seldom took place in the popular
sense of the term, except for small
depths of soft strata. The writer went
on to point out at great lengths the
various methods of boring, together
with the apparatus used on the Continent.
He remarked that the process of boring
as usually carried on consisted of essen-
tially two distinct portions. First, for
raising and the letting fall of some
heavy tool into the bottom of the bore
hole cutting up and breaking the rock
into small pieces; and, secondly, in rais-
ing the debris or sludge from the bottom
of the bore hole. Mr. Jefferson went on
to point out that the rope and windlass
which were first known and used on the
Continent are essentially the same as
those used in this country. The use of
the boring lever is not, however, so
common in this country as on the Conti-
nent, where all deep borings are gen-
erally carried on by its aid. In speaking
of the bore or boring apparatus, includ-
ing the shaft rods, which were sometimes
made of iron and sometimes of wood, he
said their breakage, especially at the
screw joints, was a thing of constant
occurrence in deep holes. Rigidity and
lightness being required, the use of
wooden rods was frequently adopted,
they being found to answer much better
when the bore hole is full of water. As
far back as the 17th century wooden
rods had doubtless been used in Russia
and Germany. In 1840 Herr Kind in-
vented the lengthening screw which has
entirely superseded the use of the chain
in deep borings. The arrangements
consist of two long side links which are
held together at the top by a sort of pin,
the nuts screwing on at the ends outside
the links. In the year 1831 borings
were comenced at ISTeusalswerk, in West-
phalia, for salt, Herr B. Von Ocynhausin
being director of the trials. In 1834
when a depth of 900 feet had been
reached, obstacles proved to be insur-
mountable, although 1300 feet more were
required to reach the deposits. Whilst
things were in that state it occurred to
Von Ocynhausin that if he could detach
the lower part of the rods — at least, so
much as was necessary for an effective
blow — he'might overcome the obstacles.
The result of such a thoughtful and
rational consideration was the invention
of a very remarkable instrument, known
as the sliding shears, or jaws. Kind's
free falling borer, which formed an im-
portant continental invention in the art
fo boring, was employed for the first time
by Herr G-. C. Kind, in 1844, in boring
at Mondorf, on the boundary between
France and Luxemburgh. The writer
then proceeded to explain that the free
falling instrument is composed of two
principal parts — viz., the free falling rod
and shears. The free falling rod is pro-
vided at the upper extremity with a
small tongue piece about 2 inches long
1^ inches wide, and If inches broad,
the bottom part of the rod being f inch
broad, and l£ inches wide immediately
below the tongue. About 12 inches
lower down two nose pins of steel are
inserted, the bottom of the falling rod
terminating on a cylindrical portion or
neck, to which the lower rods of the
boring chisel can be secured.
212
VAN NOSTRAND'S ENGINEERING MAGAZINE.
RAPID METHODS OF LAYING OUT GEARING.
By S. W. ROBINSON, Prof, of Mech. Eng., Ohio State University, formerly of Illinois Industrial University.
"Written for Van Nostband's Magazine.
Gear teeth, more than any other me-
chanical product, seem destined to suffer
for want of correct construction. Ad-
vantage seems to be taken of the fact
that errors in their peculiar form are not
so easily detected as in bodies of more
simple shape. No one would dare to
leave a hole in a link-rod three-cornered
when it is to work on a cylindrical pin.
Such a botch would, however, be much
less discoverable in its working than
errors in gear teeth. In spite of the
tale, told loud and long about every
such error, makers will still persist in
assuming the forms of teeth by guess,
because it saves trouble.
There is probably no better way of
stopping this abominable practice than
by introducing simple and easy methods
of laying out the teeth. To point out a
few such methods is the leading object
of this paper.
The circle arc has been tried as a sub-
stitute for the correct, though much
more complex curve, the epicycloid, and
with results greatly superior to guess
curves. But if a curvilinear ruler could
be found more approximative to the re-
quired curve than the circle, and present-
ing no greater difficulties in use; it, of
course, would be preferable. Such a
curved ruler we have in the Templet
Odontograph, described at length in this
Magazine of July, 1876. The methods
of setting there given were intentionally
made as free from drawing, and use of
instruments, as possible. But the ac-
companying tables often required inter-
polations to be made, a thing which
most practical men have more difficulty
with than with drawing.
But the methods of setting now to be
considered are entirely independent of
tables and mathematical work, and de-
pend solely upon simple diagrams. The
advantage of the latter is very considera-
ble in that the eye is able to detect any
error by a glance at the diagram, while
the former is accompanied by no such
check. A convenient check is sometimes
more valuable than a process.
To state briefly in words the general
method of procedure to obtain the set-
tings, it is simply to find the radius of
curvature of the desired tooth curves,
place the templet odontograph on that
radius, and strike the tooth curve.
The odontograph is especially adapted
for this, in that all the tangents drawn to
the curve of the hollow edge of the in-
strument are normals and radii of curva-
ture to the convex edge. Thus FD,
Fig. 4, page 5 of July No., 1876, Van
Nostrand's Magazine, is perpendicular
to the convex edge at I), and also FD is
the radius of curvature of the curve ADB
at D. For this reason the odontograph
may unhesitatingly be used instead of a
circle for drawing a tooth curve, the
proper tangent FD being brought to the
circle radius; that radius being so located
by construction that the point D will
fall in the midst of the arc to be used.
This point, for a face of a tooth, may be
at about a third of the height. But, to
indicate the mode of proceedure more
fully, it will be desirable to take up
special cases.
I. FOR APPROXIMATING TO EPICYCLOIDAL
TEETH WITH CURVED FLANKS.
1st. For ordinary Spur Gearing. — In
Fig. 1 let A and B represent a pair of
pitch circles touching at C; and with
ACB the line of centers. To find a face
for A, and its properly mated flank be-
longing to B; draw any circle CD HI,
with CH less than the pitch circle radius
BC. Then draw a circle through D
with the center at A, this circle being
about one-third the height from the pitch
line of A to the point of a tooth of A.
From D, where these assumed circles in-
tersect, draw a line to H, and also a line
through C produced to F. These lines
will be perpendicular to each other, be-
cause CDH is in a semicircle. Then
find I by making HI, and CI parallel to
the other two lines. Through I, draw
BIF, and AEI. Then F and E are the
centers of curvature respectively of the
hypocycloid and epicycloid passing
through D, described by rolling the cir-
cle CDH along the inside of the pitch
RAPID METHODS OF LAYING OUT GEARING.
313
P' = 2CT>
r—r
circle B, and outside the pitch circle A.
Also DE is the radius of curvature of
this epicycloid, and DF of the hypocy-
cloid at D. This completes the diagram
as far as required for drawing the ap-
proximate epicycloid through D for a
face of A, and for drawing the approxi-
mate hypocycloid through D for the
flank of B upon which the face of A, just
obtained, works.
To show that DE and DF are the re-
quired radii of curvature: call R the
radius of A, r the radius of B, and r' the
radius of CDH. Then CH=2/ and by
geometry
CD=HI : CE : : B + 2r' : R
CE R
or
OD~R + 2r'
But the radius of curvature of the
epicycloid for A is
=CE + CD=CD(EiLr+1) =
P =
2<S W
the same eq. as given in Rankine's Ma-
chinery and Milhoork, p. 60.
Similarly for the radius DF for the
hypocycloid for B we obtain
2rn
(2)
the same as given by Rankine and
others.
We have then a very simple diagram
for arriving at these radii and centers of
curvature.
The diagram may be abridged a little
in practice. Thus, it is only necessary to
draw ACB; the Pitch circles A and B;
the assumed circle G; to find D at a
third the height of the face; to make
HI=CD; and find the intersections
E and F.
In assuming the circle G, any diameter
may be chosen. If it equals CB, the
flanks will be radial, and the smaller it is
the more will the flanks be curved. A
few trials will enable the designer to hit
about right.
As regards the height of the point D,
taken at a third of the face, any height
would lead to very good results, but the
third is found to be about the most satis-
factory.
Having, now, the radii and centers of
curvature, circle arcs may be drawn if
considered sufficiently accurate, but the
Templet Odontograph will give much
better curves.
To set the odontograph, it will be only
necessary to measure the length of the
radii DE and DF in inches and tenths, to
obtain the setting number. For instance,
if DF were 2^ inches, then 2^ is the
proper number to look out on the scale
of the odontograph as indicated by the
dash at the graduated edge of the instru-
ment shown in Fig. 2. In other words,
the number 2^, as indicated in Fig. 2, is
to be brought to the point D, Fig. 1,
while the hollow edge of the instrument
is to be brought just tangent to the line
DF. This can be very conveniently
done by remembering that the 2£, for in-
stance, is exactly the distance in inches
Fig. 2.
314
VAN NOSTRAND'S ENGINEERING MAGAZINE.
from the dash, Fig. 2, to the point of
tangency in the hollow edge, as above
stated. Then DF, Fig. 1, being 2j
inches, if a sharp pencil or other point be
placed at F, and while the hollow edge
of instrument slides against it, we bring
the 2 \ point of scale at D, we have all
correct, and ready for tracing the tooth
curve through D, by passing the pencil
or scriber along the convex curve of the
instrument.
In a similar manner proceed to trace
the curve through D for the radius DE.
The latter should start from the pitch
line of A and will form the face curve
for a tooth of A, while the former should
start from the pitch line B, and will
form a flank curve for B. These posi-
tions of the odontograph are shown in
Fig. 3.
After once having found the true po-
sition of the odontograph for one face of
*$^I/
A, it may be transferred to the other
teeth in two ways. One way is to at-
tach it to a radius rod so that it will
swing around. But the other way will
probably be preferred by most draughts-
men, and consists of simply passing the
pencil around the point and heel of the
instrument while in position, and then
drawing circles, aa, concentric with the
pitch line A through these points, as
shown in Fig 3. Then by placing the
instrument with point and heel against
these circles, and in the right place for
any face, that face is readily traced.
The same procedure holds for concen-
tric circles bb, about B, for flanks.
If it should ever be desired to trace
convex flanks, it is only necessary to as-
sume the circle Gr with a diameter greater
than BC. In this case F falls to the
other side of C.
So far, we only have the faces for the
teeth of A, and flanks for B. To obtain
the faces for B and flanks for A, we only
have to repeat the construction with A
and B interchanged. In practice, this
can be done on the same diagram as that
which Fig. 1 represents, but for clearness
it has been omitted here. But the two
diagrams are entirely independent of
each other; the lines DEF differing ex-
cept when the wheels are equal.
2d. For Internal Gearing. — For this
the, figure becomes somewhat modified
for the reason that we now have epicy-
cloids running upon epicycloids, and
hypocycloids upon hypocycloids; instead
of epicycloids upon hypocycloids as
before.
Fig. 4 will indicate how to proceed.
Having the pitch circles A and B, as-
sume the circles G and G', and find the
points I and I'. Lines produced through
I and I', from A and B, will give the
center points EF, and E'F', with which
the tooth curves are to be found as be-
fore. Gr' may be assumed infinite, or, in
other words, simply draw a tangent CD"
to the pitch lines at C. Then E' and F'
fall at C. The points corresponding to
RAPID METHODS OF LAYING OUT GEARING.
315
D, Fig. 1, are to be found as in that
figure at a third the height of face. In
this figure D'F' is made to coincide with
DF for clearness of figure.
3d. For Rack and Pinion. — Proceed
as in Fig. 4, except regard CA as infinite.
Then EI is parallel to CB, and the dia-
gram is as in Fig. 5. For this case a
good result is obtained by always as-
suming the circle corresponding to G' in-
finite, or, simply taking CD' on the pitch
line CD' of the rack. CD' will then be
the radius for the face of the pinion,
while the flank will have an infinite
radius and be straight and perpendicular
to the rack pitch line.
II. FOR APPROXIMATING TO TEETH WITH
STRAIGHT FLANKS.
1st. Flanks Radial. — This case is very
simple. In Fig. 1 we have only to make
CH=CB, and hence Fig. 6. The points
F are at infinity. This would make the
flanks straight; and the fact that DB
and D'A are radii of the pitch line,
makes the flank radial. The odonto-
graph is here only to be used for the
faces of the teeth, and its setting is
made upon the radius of curvature DE,
or D'E', as already explained, by meas-
uring the radius and using the length in
inches as the setting number.
2d. Flanks Straight and Parallel. —
This is a peculiar form of tooth, said to
have been first put to practice at the
Lowell machine shop. Examples of
drawings of it were exhibited at the
Centennial by the Mass. Institute of
Technology. It is, however, simply a
special case of a general solution de-
scribed in this Magazine in August,
1876, p. 99, Fig. 2; and, according to
Willis, due to De La Hire. It is a
special case in that the flanks are straight.
But the construction is simplified in
avoiding the laying off of certan angles
by constructing the faces by drawing
numerous circles and taking their enve-
lope. This latter so reduces the work
as to give to this form of tooth its turn-
ing point of success. For a description
316
VAN NOSTRAND'S ENGINEERING MAGAZINE.
of this method for straight circular and
other flanks, see a recent number of the
Polytechnic Review.
From the well known fact that one
tooth can be assumed, and the other,
upon which it is to work, found; we
readily see that any assumed straight
flank will have its correct face of a tooth
of the other wheel upon which to work.
For our present purpose, therefore, we
only seek the radius of curvature of this
face by the aid of which, together with
the templet odontograph, that face may
be traced.
By referring to Fig. 6 or 7, we find E
the correct center *of curvature of the
face drawn through D, because the dia-
gram, as regards E, is the same as in
Fig. 1, and the same eq. (1) applies. Also
the epicycloid DJK, Fig. 7, is the one
that would be generated by rolling upon
the pitch circle A, the rolling circle
CDB, with its tracing point D.
that the point E is the center of curva-
ture of the new curve at Dr Also it is
easily seen that if DJK works correctly
upon DB, as a face upon a flank; so
DJjM, parallel to DJK, will work cor-
rectly upon DjN, parallel to DB. Again
it is evident that DDX may be assumed
at pleasure, and, of course, can be made
equal half the tooth thickness. This as-
sumption makes the two flanks of any
tooth of B, absolutely straight and
parallel.
Hence to draw teeth with straight and
parallel flanks, proceed as in Fig. 6, ex-
cept instead of D, take the point D1 a
half tooth thickness from D, and at one-
third the height of a tooth face from the
pitch line of A. This can probably be
best done by first drawing a circle to the
center B with a radius equal DDX or half
the thickness of a tooth, and then form
a right angle at Dx with a triangle, one
side against the circle, and the other at
C. Thus all the flanks are tangent to
the circle at B, and hence easily drawn.
The length ED, in inches becomes the
setting number for the templet odonto-
graph, by which a curve, closely approxi-
mating to D2 LM, can be drawn with
that instrument in the usual way.
Of course, by interchanging A and B
and repeating the above construction, we
get the other faces and flanks.
3d. Flanks Straight, but Inclining at
any Angle Toward, wr From, Each
Other. — That this form may be realized
is at once apparent from the last above,
from the fact that DDX may be assumed
of any other value than the half tooth
thickness, and the circle at B drawn.
Prolonged tangents to this circle will
form the flanks. Also what is true of
B, is true of A.
gears, rack and pinions, etc.,
be made with teeth of these
Internal
can easily
forms.
Now if we draw a curve D.LM paral-
lel to DJK; that is, made equally dis-
tant by laying off on normals DD1? JL,
KM, etc., equal lengths, we see at once
III. FOE INVOLUTE GEARING.
The new method of setting can easily
be applied to this form of tooth. The
diagram is given in Fig. 8. A and B are
the pitch lines. Draw the circle AEC
and find a point E at a third of the
height of a face of B. Draw the straight
line ECE', and the perpendiculars EA
and E'B. Then E and E' are centers of
curvatures for involutes at C; and these
can then be drawn by aid of the templet
RAPID METHODS OF LAYING OUT GEARING.
317
odontograph with the lengths EC and
E'C, as setting numbers.
Only one line ECE' is here admissible,
because the whole side of a tooth of each
wheel depends upon the one line.
We might add a method of setting the
odontograph which was pointed out by
Professor Reuleaux, Director of the
Royal Polytechnic Academy at Berlin;
and printed in a German publication. It
combines the graphical method with the
use of the odontograph tables. It is
shown in Fig. 9. A and B are the pitch
scribe the faces of A, and flanks of B.
Draw the addendum circle for A through
d. This cuts G, at a. Now with spac-
ing dividers, step off to C on the circle
G, and back equal spaces to b on the
pitch circle A. Then take the chord «C,
and lay off an equal length bd, giving
the point d, on the addendum circle.
This point will be a point in the epicy-
cloid sought.
Now with the proper setting number
found by aid of the tables, the odonto-
graph may be brought to the tangent to
the pitch line at the middle of tooth as
usual in the method of setting by the
tables, and with the edge of the instru-
ment at the point d, trace the face
curve.
The point d is seen to be correctly
located in the true face curve from the
fact that as G rolls along A, a will fall
at b and aQ will coincide with bd.
In this way of setting the instrument,
j the setting number must be obtained
i from the table with due regard to the
particular circle G assumed. To this
| end the radius of B, divided by the di-
| ameter of G, becomes the " degree of
i flank curve " for the other wheel, men-
j tioned in the tables and rules.
In the German publication above men-
tioned, one point appears to have been
overlooked in that the circle on which
j the chord Qa is to be taken was given as
the pitch circle B, instead of rolling
circle G. This may, however, have been
due to an omission by the printer, or en-
graver.
The various methods of laying out
teeth above given have been devised, as
a remedy for the- feeling of uncertainty
in the result obtained by setting the
odontograph by aid of the tables alone,
as directed in the article of July, 1876.
In the present methods the diagrams
carry certainty with them, in the check
they afford; and, it would seem, could
leave but little if anything to be desired.
The teeth can, of course, be finished
off by introduction of
in the usual way.
root curves, etc.,
circles, and G the rolling circle to de
M. H. Tresca has been elected presi-
dent of the Societe des Ingenieurs Civils
of Paris. M. Tresca was president in
1862, and is now elected for the third
time.
318
VAN NOSTRAND'S ENGINEERING MAGAZINE.
TRAMWAYS.*
From " The English Mechanic."
Teamways are now a recognised mode
of working urban and suburban traffic;
they have made their way into public
favor in the face of persistent opposi-
tion, and, instead of being removed, will
probably ultimately become the only
public means of conveyance on the main
roads leading to and between our princi-
pal towns. Tramways are not railways,
it is true, but Mr. Clark is justified in
protesting against tramway-engineering
being regarded as but a humble branch
of the profession. On the contrary,
tramways require the exercise of the
highest skill that can be found, for just
as railways in their infancy were often
failures, so tramways have arrived at the
present degree of efficiency after a series
of blunders. They cost more for work-
ing expenses than railways, and they
earn more per mile, but they are, of
course, cheaper to construct. Such a
work as Mr. Clark has placed before us
was much wanted. Sooner or later steam
or some other mechanical power will be
employed to haul the " ponderous cars,"
for Mr. Clark is not alone in the opinion
that the employment of horse-power in
the work of starting and dragging, often
on severe gradients, heavily loaded tram-
cars is an element of barbarism much
out of place in a civilized country. It
may be true that steam-cars, or the
locomotives at present devised for draw-
ing the cars, are not all that could be
desired ; but it is nevertheless a fact that
where they have been tried under suit-
able conditions they have answered the
purpose very well, considering that, as
yet, they stand very much in the same
position that Stephenson's Rocket did
to the magnificent machines that came
after it. The withdrawal of the steam
" dummies " (a dummy is a steam-car,
the engine and boiler being carried on
the same platform as the passengers)
from the Market-street route in Phila-
delphia gave rise to the idea that steam
was a failure: the fact being that the
company had not enough dummies to
work the traffic, and so, having to
* Tramways, their Construction and Working. By.
D. K. Clark, C.E. London : Crosby Lockwood & Co.
keep as many men to look after three as
would suffice for twenty, and having,
moreover, to run those three in conjunc-
tion with cars drawn by horses the ad-
vantages of steam were discounted. The
dummies are, however, objected to, be-
cause, in summer especially, they are
hot and smell badly, and it is conse-
quently seen that the direction in which
to look for a more successful application
of steam to street traffic is in the shape
of a locomotive, like that of Hughes or
M erry weather. But in that direction
we are met by two difficulties. To em-
ploy a separate motor is to lose the ad-
hesion of the car itself; and if the engine
is made heavy enough to provide suffi-
cient adhesion to enable it to drag the car
up any gradient on the road, it is proba-
bly too heavy for the permanent way,
which will consequently require con-
tinual and costly repairs. The self-con-
tained or steam-car has, therefore, one
great advantage over that drawn by a
locomotive — that it is best adapted for
the tramways at present laid; but there
is no doubt that when once Parliamentary
sanction is obtained for the employment
of steam or other mechanical power,
without unnecessary restrictions, the
demand for motors will be met by the
invention of the engine required. Mr.
Clark divides his work into five parts,
and presents us with an enormous col-
lection of facts carefully arranged for
the guidance and instruction of the engi-
neer and the capitalist. His first part
is a history of the origin and progress
of tramways, from the early timber rails
employed 200 years ago to the elabo-
rate arrangement of rails, ties, and sleep-
ers adopted in this country and abroad.
The wooden tram-rails were occasionally
plated with wrought iron, but in 1767
the Coalbrook Dale Company determin-
ed to protect their oak rails with cast-
iron, because the price of iron being very
low, and not wishing to blow out the
furnaces, they were in a difficulty as to
stocking. Accordingly they cast the
iron into pigs 5 feet long, 4 inches wide,
and li inches thick, with three holes,
through which they were fastened to the
TRAMWAYS.
319
timber rails. By this means they made
the iron help to pay the interest by re-
ducing the cost of repairs, and the pigs
were there at any time when wanted.
The modern tramway was first employed
in the United States, where, owing to
the badness of the roads and the long
distances to be traversed, a rapid means
of transport was the first necessity to
the pursuit of business. The New York
and Harlem line was opened in 1832, but
did not meet with favor, and was for a
time suppressed. In 1852, however,
M. Loubat, a French engineer, laid down
a tramway in New York, consisting of
rolled iron rails placed upon wooden
sleepers. The rails had a wide groove
in the upper surface, and were similar to
those afterward laid down by the same
engineer in Paris. Tramways had by
this time become so essential to New
York that the objections made to them
by the proprietors of other vehicles were
disregarded, and they multiplied rapid-
ly, not only in the Empire city, which
owes most of its amazingly rapid de-
velopment to them, but in the principal
towns of the States.
Mr. Clark speaks of the "fearless
manner" in which the rails were propor-
tioned, but they were tolerated because
the tramways were of more importance
than the comparatively few vehicles
which traversed the streets. In 1856 a
Mr. C. L. Light, an English engineer, laid
an improved tramway in Boston, in
which the depth of the groove was only
% inch, while the inner side of the rail
formed a flat slope. The Philadelphia step
rail was also an improvement, dispensing
with a groove altogether, but having a
ridge at one side against which the
wheel -flanges ran; it answered its pur-
pose well, and is still in use in that city,
while a similar pattern has been adopted
for New York. In fact, the step-rail
may be said to be that most generally
used in the United States. When intro-
duced to England by Mr. Train it was
speedily condemned, and the lines laid
by him at Birkenhead and the Potteries
were only saved from suppression by
the substitution of flat grooved rails of
the kind with which we have since be-
come familiar. The modern practices,
for there are several methods still, as it
were, under trial, are fully explained in
Mr. Clark's book, and the numerous
woodcuts and lithographic plates render
his work of great value. The present
practice of tramway construction forms
the second part of the book, and the
many tables of cost and working expend-
iture which he has inserted in part
three will be studied with attention by
the municipal authorities and capitalists
Part four introduces us to what may be
termed the mechanical portion of the
subject, although it is confined to a
description of tramway cars. It is im-
possible, within the limits we can devote
to a notice of this book, to give" even an
outline of the many details of the num-
erous cars which Mr. Clark describes.
It must suffice to say that examples of
the best constructions are fully illus-
trated, and that the latest improvements
are noticed, down even to Eade's revers-
ible car, which was patented in 1877.
This car is swiveled centrally on the
underframe, so that after the locking
apparatus is unfastened, the driver can
turn the car round without leaving his
seat. This arrangement avoids the nec-
essity for shifting the horses and pole,
and the car is, of course, constructed with
only one door and two staircases to the
roof, one on each side of the platform.
Mr. Clark says it is reported that the re-
versible car effects a saving of 30 per
cent, in the horse-power required — a
stud of eight horses working it as effi-
ciently as twelve work the ordinary car.
Eade's car is unusually light, weighing
empty only 34 cwt, while one wheel on
each axle runs loose. The alleged sav-
ing in power is, of course, due to the
lightness of the car not to its reversibil-
ity. It is in use on the Salford tram-
ways. The fifth part, Mechanical Power
on Tramways, will be of most interest
to the great majority of readers, for the
development of the tramways system
depends almost entirely on the applica-
tion of mechanical power for their work-
ing. The report of the Select Committee
issued recently will probably give a stim-
ulus to the introduction of steam and
compressed air motors, though they will
still be hampered by restrictions which
seem, to those familiar with engines, to
border on the absurd. Mr. Clark in his
historical sketch of the application of
mechanical power to tramway cars, com-
mences with Latta's "dummy," put on
the Cincinnati Tramway in 1859. The
320
VAN NOSTRAND's ENGINEERING MAGAZINE.
earlier efforts of Trevithick and others
are ignored as not, strictly speaking,
belonging to the subject. Mr. L. J.
Todd was, however, the first engineer to
bring forward any practical designs for
the employment on roads of steam-pro-
pelled tramcars; and, we believe his
engines were the earliest which met all
the conditions imposed — viz., the ab-
sence of noise, smoke, and steam, with the
possession of the power of stopping and
starting quickly. About the same time
Dr. Lamm experimented with an ammo-
niacal-gas car, and demonstrated the
practicability of the invention; but the
necessity for preventing all escape of
the gas, together with its chemical action
on iron, led Dr. Lamm to abandon for a
time his ammonia engine in favor of the
fireless locomotive, which consists of a
strong well-clothed reservoir filled with
water at a very high temperature. The
fireless locomotive is running on the line
about six miles in length, between New
Orleans and Carrollton, the stationary
steam-generator being at the, latter
place. The reservoir of the locomotive
is filled with cold or preferably warm
water, and then is connected to the
Carrollton boiler, and steam of 200
pounds pressure forced in. The water
is thus quickly heated and a pressure of
about 180 pounds per square inch ob-
tained. The contents of the reservoir is
about 60 cubic feet, and in practice it is
found to contain sufficient steam to run
the car from Carrollton to New Orleans
and back without reducing the pressure
much below 50 pounds. The exhaust
was discharged into the atmosphere
making clouds of moist white vapor.
Two other fireless locomotives were
tried on the East New York and Canar-
sie Tramway, but they were not so suc-
cessful as Dr. Lamm's. About this time
Mr. Baxter, in America, and Mr. John
Grantham, in this country, brought out
steam-cars. Baxter's had an engine
with compound cylinders and carried 54
passengers; and Grantham's, which was
the first steam- car actually built and
tried in England, had a boiler on each
side of the body, in the center of its
length with the engine underneath. It
carried 44 passengers and worked well
enough on the trial line at Brompton,
but failed when tested on the line be-
tween Vauxhall Bridge and Victoria
Station. It was removed to Wantage,
but was unfitted for the inclines and
curves of that tramway. It was subse-
quently altered by the advice of Mr. E.
Woods, who replaced the two separated
boilers by one, which was completely
boxed in, and served to divide the car
into portions, leaving a passage at one
side communicating between the first
and second class divisions. One pair of
the wheels was used for driving and one
wheel of the other pair ran loose, for
ease in passing curves. It accommodated
60 passengers, and its estimated cost,
from experience of its work on the
Wantage line, was less than 4d. a mile
run. Mr. Woods recommended that the
Grantham car, built for the Vienna
tramways, should have the boiler and
engine placed at one end, while instead
of the loose wheel on the undriven axle,
he proposed a four wheel bogie. This
car was fairly successful, but the boil-
er though a rapid generator, was too
limited in water room, and required very
skillful management. On a good road
the working speed is from 10 to 12 miles
per hour. In 1874 Mr. Loftus Perkins
designed a tramway locomotive for a
Belgian company. It was worked at a
pressure of 500 pounds on the square
inch, and had compound engines, the
high-pressure cylinder being single-act-
ing. The steam exhausted into an air
surface condenser, consisting of a number
of copper tubes. The boiler was of
bent iron tubes 2^ inches in diameter
(inside) and f inch thick, tested to 2,500
pounds on the square inch. Coke was
the fuel, the draught being due to the
height of the chimney alone. The speed
of the crank shaft was reduced by
toothed gearing in the ratio of four to
one, and the motion was taken off the
second shaft to the wheels of coupling-
rods. At the commencement of its
working life this locomotive was re-
ported to be perfect — "no smoke, no
escape of steam into the atmosphere, no
noise, no feeding of water during the
trip, nor even, if needful, for several
days." The high pressure, however,
rendered it very difficult to maintain the
joints, and after altering the engine, the
Belgian authorities concluded to take it
to pieces and sell it as old metal. Mr.
Perkins has, however, recently improved
his design, and Mr. Clark says at the
TRAMWAYS.
321
conclusion of an elaborate description,
accompanied by an excellent lithograph,
that " it is anticipated that very econom-
ical results of performance will be ob-
tained by the use of this locomotive.
The Societe Metallurgique et Charbon-
niere of Belgium constructed a tram-
way locomotive in 1875, with a Brother-
hood three- cylinder engine and a Bell-
ville " inexplodable boiler," the speed
being reduced by spur gear. It resem-
bles an omnibus in appearance, and alto-
gether is scarcely likely to become the
motor of the future. Of the numerous
devices that have been tried we can only
allude to Francq's improved hot-water
locomotive, in which the steam from the
reservoir is admitted to an intermediate
chamber, where it is maintained at a
fixed pressure; to Todd's hot water
steam-car, in which the reservoir and
machinery is carried beneath the floor;
to MM. Bede & Co's hot-water steam-
car which has been running regularly
and successfully in Belgium, and to the
engines of Merryweather, Hughes, H. P.
Holt, Ransom, and Baldwin, the two
former of which are well known from
description, already published. Most of
the designs are illustrated by diagrams,
and some have large lithographic plates
devoted to them. It will be understood,
from what we have said, that Mr. Clark's
work is a perfect treasury of tramway
facts, but it is even more than that,
because some of his chapters are occu-
pied with dissertations on the principles
of tramway construction and working,
in which points apt to be overlooked by
inventors are carefully considered. Cars,
he thinks, should be constructed on
double bogies, or, still better, on radiat-
ing axles, and they should have a longer
wheel base than is now usual. The re-
sults obtained with the Paris omnibus
car, Mr. Eade's car, and Mr. Cleminson's
flexible wheel-base car, point to the de-
sirability of starting afresh with new
ideas, and recasting the design of the
tramcar. The production of a noiseless,
vaporless, smokeless, and handy machine
will not come from those who too slav-
ishly follow the old lines; but of the
present devices Mr. Clark awards the
palm, as first in order, and foremost in
practical performance, to the Merry-
weather, which in Paris and in other
parts of the Continent has been doing
effective service on the tramways,
" causeless of annoyance or hinderance
to the ordinary traffic of the streets."
It is too much to hope that this work
will lead to the prompt withdrawal of all
vexatious restrictions on the use of me-
chanical power for propelling street cars;
but, while it places a vast amount of
practical information before the engineer,
it serves to enlighten those who may
ultimately have to decide whether a me-
chanical power tramway shall or shall
not be allowed in the districts over
which they have control.
COTTON POWDER OR TONITE.
From "The Engineer."
One of the marvelous applications of
chemistry is the discovery of the modern
explosives known as nitro-glycerine, gun-
cotton, dynamite, litho-fracteur, and
under other names. The late war, and
especially the destruction of the two
Turkish monitors, the general introduc-
tion of torpedoes and torpedo vessels,
the destructive explosion at Stowmarket,
the disaster, fearful in every sense, at
Bremerhaven, have directed even popu-
lar attention to these extraordinary sub-
stances. Like other forces of nature,
powerful servants but evil masters, these
Vol. XIX.— No. 4—21
materials render very great services in
many operations ; and, in case we have
a war, our control of the manufacture of
most of them should be of the greatest
importance. There is now a competitive
struggle going on between the different
blasting explosives in the market, and
only time will tell which one will obtain
the mastery. All of them evolved in
the laboratories of chemical analysts,
their introduction has undergone many
vicissitudes ; and enormous labor and
sums of money have had to be spent
before they could be rendered practically
322
VAN NOSTRAND7S ENGINEERING MAGAZINE.
useful. On the introduction of gun-cot-
ton by Schoenbein in 1846, great expect-
ations were at once raised, experiments
on a lavish scale were carried out with
it, especially by the Austrian Govern-
ment ; but in the course of a few years
it was relegated to the laboratory shelf.
About 1860, Sobrero introduced his
nitro-glycerine ; but Herr Nobel had to
render it practical by mixing it with an
earthy absorbent, producing what is now
called dynamite, before it could be ren-
dered what may be termed chemically
stable and a fairly safe article for blast-
ing purposes. Again taking up gun-
cotton, Professor Abel has rendered it
similar services, mainly by pulping its
fibre, and by thus rendering the texture
uniform, enabling it to be more thor-
oughly washed. The Stowmarket explo-
sion, however, showed the necessity of
using it in the wet state, as it was fortu-
tunately discovered that it could then
be exploded by the use of a strong
primer of dry gun cotton.
As we are all accustomed mentally to
compare an explosive with ordinary gun-
powder, at first sight scarcely anything
is stranger than to see a quantity of
matter embodying an appalling amount
of explosive force harmlessly burning
away like a candle. But the compara-
tive safety attending the use of modern
explosives known under the names of
gun-cotton, lithofracture, tonite or cot-
ton powder, is due to the fact that they
cannot, under ordinary circumstances, be
exploded without the application of a
special detonator. But most of them are
liable to more hidden and insiduous in-
fluences. While gunpowder only ex-
plodes by the heat generated by friction,
or by the direct application of a flame or
spark, dynamite, for instance, is liable
to explode unexpectedly while being
thawed; and the union of the nitric radi-
cle with the glyceric elements being of a
weaker character than the similar union
in gun-cotton, it follows that the origin-
al nitro-glycerine of dynamite will not
resist the external disruputive forces
that can be applied to gun-cotton — such
as accidental concussions. This has
been proved theoretically by M. Berth-
elot, well known for his work in these
departments of applied science. He
found by direct experiments that the
mean of the molecule of the radicles
gives less heat in the formation of nitro-
glycerene than is the case with gun-cot-
ton and that the ratio of these values
also gives the value of the ability of the
compounds to withstand disruption.
The habitual practice of the respective
manufacturers in supplying detonators
twice as strong for gun-cotton as for ex-
ploding dynamite is unwitting practical
proof of Berthelot's discovery. Dyna-
mite is thus probably out of the ques-
tion for general use in military opera-
tions, on account of its property of freez-
ing at a comparatively low temperature;
and it is an open question "whether the
damp compressed gun-cotton now sup-
plied to the British army and navy,
could be exploded in a mine laid over-
night in frosty weather. It has often
been stated that dynamite could be
thrown on a fire without causing an ex-
plosion; and this might indeed happen,
but we should be sorry to be present at
several such trials. Compressed gun-
cotton, while wet of course, stands this
fire test very well; but it can only be
called wet when there is no occasion for
the necessity of its standing this test at
all, or when it is stored in water-tanks.
Once out of such tanks the water begins
to evaporate, and, in fact, some of the
gun-cotton must be dried before any can
be used. Hence, as in the case of thaw-
ing dynamite, dry gun-cotton has to be
put in close proximity to heat, and as the
substance is then highly inflammable and
porous, there is liability to an explosion.
In theory there is only one element to
be taken into account in estimating the
blasting value of an explosive, namely,
the total heat it can evolve. But> in
practice, on account of the very different
amounts and natures of the resistance of
the bodies to be acted upon, a time ele"-
ment is introduced. The element of
space is also a not unimportant factor.
For instance, if 1 pound of compressed
gun-cotton and 1 pound of common gun
powder be confined within a solid resist-
ing mass of rock or metal, it will be
found that the pound of compressed gun-
cotton contains less than twice the energy
of gunpowder. If, on the other hand,
equal quantities by weight of the two
be exploded freely on a common iron
rail, while the gunpowder would cause a
mere puff of smoke, the gun-cotton
would completely shatter the rail. The
COTTON POWDER OR TONITE.
323
rate of explosion of compressed gun-cot-
ton is nearly 18,000 feet per second.
This extreme rapidity of explosion en-
ables the inertia of its own mass to act
as sufficient tamping, while the compara-
tive slowness of the gunpowder explosion
gives the gases full liberty to expand in
the measure as they are generated.
It is a necessity inherent to the very
nature of any explosive that it cannot
ever be termed absolutely safe; it is only
comparatively safe under certain known
conditions. Thus, a great recommenda-
tion of ordinary gunpowder, when made
with sulphur free from sulphurous acid,
is its chemical stability; it also explodes
at a high temperature, but its hardness
makes it liable to ignite by friction; and,
differing from the new blasting explo-
sives, it is easily exploded by a spark.
But it is the chemical stability, mainly
due to the knowledge acquired during
the centuries of time in which it has
been manufactured, that makes it so
much safer to store. The great danger
from ordinary gun-cotton is this, that it
is liable to chemical changes subsequent
to manufacture. Such changes seem to
be due to irregularities in the composi-
tion, to mechanical and chemical non-
homogeneousness. This tendency to
alteration is corrected by the system of
grinding, boiling, and washing, which
removes any free acids and organic com-
pounds mixed with the fibre. But in spite
of all this, it has still to be kept and used
in the wet state, which if leading to
nothing worse, is conducive to miss-
fires. It is also liable to another danger.
Its combustion or explosion evolves car-
bonic oxide, one of the most poisonous
gases known, and the cause of the late
accident in the Holywell district, by
which one miner was suffocated and
fifteen more or less injured.
There is a form of gun-cotton known
as tonite, or cotton-powder, which is said
to possess rather peculiar properties. It
is tolerably well known as a marketable
commodity, and manufactured on a
large scale near Faversham. Tonite
consists of finely divided or macerated
gun-cotton compounded with about the
same weight of nitrate of baryta. The
gun-cotton itself is mainly common cot-
ton waste steeped in nitric acid, and on
the excess being forced out by a hydrau-
lic press, or otherwise, it is left some
time for digestion in vessels of clay.
Necessarily while in the moist state, the
fibres are macerated or disintegrated
between crushing rollers. In order to
give this substance what is to be com-
plete chemical stability, it is subject to
washing processes, the rationale of which
is a secret of the maker, and which com-
plete the manufacture of the gun-cotton.
Tonite consists of this macerated gun-
cotton, intimately mixed up between
edge-runners, with about the same
weight of nitrate of baryta. This com-
pound is then compressed into candle-
shaped cartridges, formed with a recess
at one end for the reception of a fulmin-
ate of mercury detonator. In the fact
of its being easily fastened to the safety
fuse, it contrasts very favorably with
soft, plastic, dynamite. Amongst the
advantages said to result from the use
of the nitrate are that it contains a
great amount of oxygen in a very
small volume; and that it is very ready
under the detonator, while its great
density makes it slow to the influence of
ordinary combustion. By the employ-
ment of nitrate of baryta it is claimed
that this explosive cannot merely be
made much cheaper than ordinary gun-*
cotton, but that the same weight is
about 30 per cent, stronger. It may seem
incredible, but a tonite cartridge is no
more liable to catch fire than a piece of
soap, which it resembles; its great den-
sity causes it to burn very slowly if set
fire to, and so slowly that all danger
from a too violent generation of gases is
obviated. While, therefore, the rail-
ways of the kingdom absolutely refuse
to carry dynamite and compressed gun-
cotton, they regularly take tonite on the
same footing as gunpowder. The tonite
cartridges are generally waterproofed.
The density is such that it takes up the
same space as ^dynamite, and two-thirds
of gun-cotton. There can be no doubt
that mu«h original chemical thought
has been practically applied by the offi-
cials of the Cotton Powder Company,
and they claim, probably with justice, to
have taken a lead in the introduction of
processes for the purification of nitro-com-
pounds — in other words, to have given
them sufficient chemical stability as to
obviate those dangerous internal changes
subsequent to manufacture at the bot-
tom of so many disasters.
324
VAN NOSTRAND'S ENGINEERING MAGAZINE.
ARTIFICIAL MARBLE.
From " The Building News."
A process of making artificial marble
has been recently patented in England
on behalf of Harriet G. Hosmer, of Rome,
which differs from previous processes in
the fact that limestone in the solid state
is employed as the base instead of a
mixture of plaster and cement. The
limestone is worked by any suitable
means to the desired form, and is then
placed in a boiler furnished with a
safety-valve and manometer, so that the
pressure therein may be noted and con-
trolled as may be required. The boiler
is then filled with pure water at the
ordinary temperature, care being taken
that there is no mineral deposit intro-
duced with the water. Care must also be
taken that the water completely covers
the objects placed within the boiler. The
boiler is then hermetically sealed, and
fire applied, and the water allowed to
boil until the manometer indicates five
"degrees" of atmospheric pressure if the
objects are small, and six or seven de-
grees of pressure if the objects are large.
When the heat reaches the above-men-
tioned point the water is allowed to cool
until the pressure indicated by the man-
ometer returns to zero. The water is then
taken out of the boiler, either by means
of a pump or a siphon, and the objects
are removed from the boiler preparatory
to being placed in the alum or colored
bath. If, however, steam alone can be
introduced into the boiler (always main-
taining the above-mentioned degree of
heat and pressure) the result attained
will be the same, the action of the steam,
not the presence of water, being neces-
sary for acting on the stone. When it is
desired that the objects should retain
the natural color of the stone, the alum
bath should consist of pure water con-
taining five degrees of alum, as indicated
by the areometer. The articles must
remain in this bath at least twenty-four
hours, but they may be left in the same
bath for a week, or for a month even, by
which time they will acquire still greater
hardness. The stone will, however, have
become sufficiently petrified for all ordi-
nary purposes in twenty-four hours. If
pure water be used in the boiler, accord-
ing to the process first described, instead
of steam, the alum bath may be effected
in the boiler itself, thus avoiding the
necessity of removing the objects; but it
must be remembered that the application
of alum is only admissible when it is in-
tended to preserve the natural colour of
the stone. > In such case the alum is put
in the water before the boiling commenc-
es, and the objects must remain in the
boiler for 24 hours after the pressure, as
indicated by the manometer returns to
zero. The articles, when taken from the
alum bath, may pass into the hands of
the polisher if in the form of plain
blocks, slabs, or flat pieces, but if they
be in the form of statues, busts, vases,
columns, or other ornamental works of
art, they may be placed in the hands of
an artist to finish, if required, as the
stone does not attain its greatest hard-
ness until it has become perfectly dry,
which will require a fortnight, more or
less, according to the size of the object.
When it is desired to impart color to
the stone the colored baths are prepared
in the manner indicated below, in which
the objects must be immersed, and must
remain therein at least 24 hours. The
colored baths must be boiling, or very
nearly so, and it is better to remove the
objects to be colored from the first
boiler and place them in the colored
liquid while they are still warm from the
steam or water. There is no danger,
however, of injuring the stone, even if it
should be put into boiling liquid while
cold, or into cold water while the articles
are still heated, but the color penetrates
deeper when both stone and bath are in
a heated state. If it be desired to place
an object a second time in the colored
bath in order that it may acquire a
deeper colour it should first be placed in
an oven at a temperature of from 80 to
90 degrees, in which it may remain ten
minutes, after which it may be immersed
in the colored bath. To produce black
or dark grey color take of pure water
2 litres; red wood, 300 grammes; fustic
wood, 120 grammes; sulphate of iron, 10
grammes; sulphate of copper, 2j gram-
mes. Boil the red wood and fustic wood
AKTIFICIAL MAEBLE.
325
for an hour and a half, then add the Sul-
phates, and continue the boiling until all
the salts are dissolved. Three or four
minutes will probably be sufficient for
this purpose, the solution may then be
passed through a sieve, and half a tum-
bler of acetic tincture of iron added.
Stone color or lighter grey is obtained
in the same manner, with a weaker solu-
tion. In order to prepare a red coloring
solution take of pure water 3 litres;
Brazil wood, 330 grammes; Scotaus (sic),
5 grammes; cream of tartar, *1 gramme;
alum, 1 gramme. Boil the mixture until
all the color of the wood is extracted,
and then pass the solution through the
sieve in order to remove therefrom any
solid matters that may be held in suspen-
sion therein. A yellow color is obtained
by adding to three litres of pure water
extract of yellow wood of Cuba, 20
grammes; sulphite of magnesia of alum,
10 grammes. The mixture must be boil-
ed until complete solution of extract is
effected. In order to obtain a green
color dissolve in three litres of pure
water extract of yellow wood of Cuba,
20 grammes; and 10 grammes of alum.
Boil the ingredients as above and then
add carefully (by means of a wooden
spoon, and keeping at a certain distance)
as many drops of acid sulphate of indigo
(Saxon blue) as may be necessary to
give the tone of color desired. To ascer-
tain the depth of color pour a few drops
upon white paper, or dip a piece of dry
plaster of Paris in the solution. For a
blue color dissolve alum, 10 grammes;
acid sulphite of indigo, 20 grammes in
8 litres of water, until the desired color
is obtained. As all the varied colors of
aniline penetrate the stone perfectly,
they may be used at pleasure. It is
only necessary to dissolve the color
selected in a little alcohol, which is after-
wards diluted with warm water, in which
alum is dissolved in the proportion of 24
grains of alum to every litre of water.
The solution may be even stronger in
alum; this is for colors which are insol-
uble in water. For such aniline colors
as are soluble in water no alcohol is nec-
essary. They may be dissolved in boiling
water in which a little alum or sulphate
of magnesia is introduced. Care must
be taken to select only those colors
which are durable. The same colors
which are permanent in cloth are perma-
nent in stone, and in general the same
rules which apply to the art of dyeing
cloth may be applied to the art of dyeing
stone. Pavements which are colored,
particularly if the color is very delicate,
and if there be fear of dampness, are
better laid down in cement of a light
color. For the darker colors the
cheaper dark cement is equally good.
For the stone of which the natural
color is preserved no cement is abso-
lutely necessary unless the place in which
they are to be laid is particularly damp.
After the objects have been taken out of
their respective baths they are allowed
to dry, during which process the work
may be re-touched, if necessary. When
dry they are reduced to a fine surface by
means of pumice stone, after which a
still finer surface may be given by means
of a piece of slate, or still better, of lead,
after which they may be rubbed with oil.
When the oil is dry the articles may be
rubbed with phosphate of lime, and the
lustre will be rendered perfect. The
ordinary methods of polishing marble
will apply to the polishing of petrified
marbles prepared by the above process.
The survey of the silver mines situ-
ated on the Comstock Lode was carried
on in 1877 by Professor J. A. Church, of
Lieutenant Wheeler's party. The char-
acter of the vein was carefully mapped
from one thousand feet to two thousand
feet deep. The heat varied from 84°
Fah. in old drifts, to 116° in freshly
opened workshops. The source of this
heat is, it is believed with those in charge
of the works, ascertained to be the de-
composition of rocks under the agency of
atmospheric influences. This was ob-
served of the thick sheets of lava lying
upon the vein in the upper 1,000 feet
of rock. Below this, it is known to be
going on for 1,500 feet further; at 2,400
feet it is nearly uniform, neither increase
nor decrease is observed. The miners
cut through singular bands of hot and
cold rocks, a fact which seems to suggest
that the origin of the local heat is the
motion which is taking place is tangen-
tial and orthogonal directions in the
earth's crust, as the result of its slow
contraction by cooling. It is thought
the lode will continue hot, but not in-
creasingly so.
326
VAN nostrand's engineering magazine.
THE FLOW OF SOLIDS.*
By M. HENRI TEESCA, President of the Societe des Ingenieurs Ctvils, Paris.
From "Engineering."
For all bodies two distinct periods are
recognised — the period of perfect elasti-
city, which corresponds to variations of
length proportional to the pressures
applied ; and the period of imperfect
elasticity, during which the changes of
dimensions, on the contrary, increase
more rapidly than the pressures. If the
second phase of deformation be alone
considered, it is easily understood that it
leads finally towards a condition in which
a given force, sufficiently great, would
continue to produce deformation, so to
say, without limit — such as may be ob-
served in the process of drawing lead-
wire. This particular condition, in which
the deformation is indefinitely augment-
ed under the operation of this great
force, constitutes in fact the geometrical
definition of a third period, which has
been designated by the author as the
period of fluidity, and to which the
greater part of his experiments on the
flow of solids are related.
The period of fluidity is more extended
for plastic substances; it is necessarily
more restricted and may altogether dis-
appear in the case of vitreous or brittle
substances. But it is perfectly develop-
ed in the case of the clays and in that of
the more malleable metals.
In his paper of 1867, the author con-
sidered the deformations of these sub-
stances by flow under certain given
conditions ; such as the flow of a cylin-
drical block through a concentric orifice,
or through a lateral orifice, one of the
most novel subjects of his researches ;
also plate-rolling, forging and punching.
It was there demonstrated that in these
different mechanical actions the pressure
was gradually transmitted from place to
place, with loss from one zone to another,
in absolutely the same manner as in the
flow of liquids, and with a regularity not
less remarkable, but following a much
more rapid law of diminution.
The pressure may be very considerable
at certain points, whilst it may be noth-
ing at all at other points, and the study
* Paper read before the Institution of Mechanical Engi-
neers.
of the various modes in which pressures
may be transmitted constitutes in fact a
new branch of investigation to which M.
de Saint- Venant has given the name of
plasticodynamics. It is chiefly in the
operations of punching metals that this
mode of transmission of pressure has
been manifested, whilst the processes of
forging, on their part, have afforded the
means of establishing the correlation
between those molecular phenomena, and
the development of heat which is their
direct consequence.
With respect to the formation of the
jets of solid matter similar to jets of
liquids, one more experiment only will
be referred to, of recent date, by which
the likeness is completed, and becomes
absolutely illusive.
Two half discs of lead, forming por-
tions of a cylinder, four inches in diame-
ter, were placed in juxtaposition in the
compression-press, so as to form a whole
disc. Under the pressure of the piston
they resolved themselves into a cylindri-
cal jet, identical in appearance with
those jets which had previously been
obtained, but formed in reality of two
semi-cylindrical jets in perfect contact.
Their surfaces of contact bore especial
traces of the successive movement of the
different layers, and reproduced the
exact representation, in the solid state,
of a sheet of water in motion.
Punching. — Regarded as a question of
kinematics, the punching of various
substances, as wax, clay, plastic metals,
supplies instances of absolutely identical
deformations. Shortly after the paper
of 1867, some nuts which had been man-
ufactured by punching hot, in England,
and which were sent to the author by
the kindness of Mr. Bramwell, enabled
him to remark the same effects, still
better developed by the phenomena of
the drawing of the fibres, so well mani-
fested in the specimens now lying on the
table.
The two punches, which act in oppo-
site directions, enter the block of metal
from opposite sides, and the piece which
is left between them is diminished in
THE FLOW OF SOLIDS.
327
thickness by flowing from the center
towards the circumference, until, when
the two punches are moved in the same
direction, the piece reduced to a mini-
mum thickness is shorn off and dis-
charged outside.
The phenomena which take place in
this metal, softened by heat, are such
as would take place in a liquid ; and
they lead us to expect that the deforma-
tions observed in punching lead should
be produced similarly in analogous oper-
ations on the hardest of metals.
The author had already shown the
inflexion and the curving of the fibres by
the punching of discs of cold iron, at the
works of MM. Cail & Co., and also the
same phenomena in the burrs which
were punched out; but he had not been
able, on account of the insufficiency of
his apparatus, to obtain, with iron, as
much reduction of the height of the burr,
as was obtained in his experiments with
more plastic substances.
The section of one of these burrs, taken
in a vertical plane through the axis, does
not admit of any doubt of the deforma-
tions produced.
In a special memoir presented to the
Academy of Sciences, on the 3 1st De-
cember, 1869, the author endeavoured,
on the basis of an enlargement of the
burr in the zone of fluidity, as it is called,
just under the punch, to establish a
general formula for the measure of the
reduction of the height of the burr,
taken into account the whole height of
the burr, its diameter, and the diameter
of the punch. The height L was given
by the formula:
L=R(l+log.|)
in which R and Rx represent respectively
the radius of the burr, supposed to be
cylindrical, and the radius of the punch.
When the punch penetrates it forces
the material to spread laterally, until the
moment when the solid unaltered portion
below presents a less amount of resist-
ance to shearing than is applied to the
continuation of the lateral spread. This
argument suffices to show that all burrs
of the same section should be of the same
height.
By the results of another and supple-
mentary series of experiments, it was
established that for all the different
materials, subjected to the same action,
the results were substantially alike, and
corresponded exactly to the dimensions
given by the formula.
But, at that time, the author was
unable to experiment with blocks of iron
sufficiently thick to embrace a range of
evidence as to the reduction of the height
of the burr, such as had been obtained
with other materials; and it is only quite
recently that the results of experiments
on punching made in America have
appeared, and have in a remarkable
manner confirmed a posteriori the results
of his previous investigations.
Several specimens of these punchings,
very skilfully prepared by Messrs.
Hoopes & Townsend, have been forward-
ed from the Philadelphia Exhibition, to
the author. But the burrs proved a
^ little longer than the lengths as deduced
by means of the formula; the fact being
that the blocks which were sent had
been planed after the burrs had been
punched out, to dress the faces. When
the actual unplaned blocks arrived, they
satisfaetorily confirmed the algebraic
formula.
The reduction of height seemed at first
incomprehensible; and it can only be
explained by the flow of a portion of the
material into that of the block. It is to
be remarked, too, that the lower face of
the burr is convex, and the upper face is
concave; with respect to the latter, the
punch only crushes the material at the
edge, whilst the middle of the face, not-
withstanding the forced passage through
the block, retains the original tool-marks.
The formula is deduced, as has been
seen, from certain hypotheses on the
mode in which pressures are transmitted ;
and though it be only a particular case
of more general formulas, cited in the
author's memoir on punching, it retained
somewhat of an empirical character.
Thanks to the researches of M. Bous-
sinescq, in his theoretical essay on the
equilibrium of pulverulent masses com-
pared with that of solid masses, it takes
its place as a rational formula, and it
may therefore be accepted with complete
confidence.
In one specimen only of all those
which have been prepared by Messrs.
Hoopes & Townsend, the pressure exert-
ed by the flow of the metal has burst the
block, and, on a close examination of the
328
VAN NOSTRAND'S ENGINEERING MAGAZINE.
bottom of the cavity formed by the
punch, in consequence of the mode by
which the pressure was transmitted, all
the features of the results of the explo-
sion of a projectile there may be found.
A few more sketches of punched
blocks are added, showing precisely the
contortions produced in the lines of junc-
tion by the passage of the punch.
It would be unpardonable if, on this
occasion, no mention were to be made of
the remarkable experiments on iron com-
pressed when cold, the results of which
have already been presented at the
Vienna Exhibition, and which have until
now been only received with doubt, and
even with incredulity.
Can the quality of iron be really
improved by cold-compression ? There is
no longer room for doubt as to this, in
view of the recent researches of Profes-
sor Thurston, and the numerous speci-
mens which are to be found in the
collection of Messrs.Hoopes & Townsend,
with the actual particulars of the forces
under the action of which they were
ruptured.
Speaking now only of the experiments
with nuts when punched cold, Professor
Thurston's tables indieate a considerable
augmentation of resistance relatively to
nuts of the same dimensions made of the
same iron, and punched hot. The trials
were made, either by applying to the rod
which carried the nut pressure sufficient
to strip the thread, or by introducing
into the unscrewed nut a conical mandrel
sufficiently loaded to split the nut. The
augmentation of resistance due to cold
punching may be taken at an average of
25 per cent, and this result can only be
explained by supposing that there is
some modification of the molecular con-
dition of the surrounding iron, which has
been subjected to compression by the
flow from the mass of metal driven out
by the punch.
Forging. — If it be necessary to justify
the expression, flow of solids, in the case
of forgings, it is only needful to prove it
by the inspection of a collection of speci-
mens of rail scalings, found on the East-
ern Railway, near Epernay. Each blow
is in some sort represented by the forma-
tion of a wave, and drawing-out has
taken place in this fashion, by the
formation of successive scales for a
length of several decimetres. Deforma-
tions produced by forging only differ
from this mode of displacement of the
molecules in this, that they are produced
for a certain purpose, and at a tempera-
ture at which the metal becomes com-
paratively soft.
The object of the author's early
discussions on the forging of iron was
to show the tendency to parallelism of
all the fibres which originate in drawing
out under the hammer, and which are
separated from the neighboring fibres by
a cementing substance derived from the
incorporated cinder, which fills up all the
void spaces between the fibres. This
matter is frequently of a vitreous nature,
very rich in oxide of iron, and when it is
not burned off or pulverized at the sur-
face of the piece when in the hands of
the smith, it follows all the varieties of
form to which the piece is shaped in its
several parts. It has been shown, never-
theless, that the deformation may be
only superficial when the action of the
hammer was mild, whilst the influence of
a more powerful blow, such as is prac-
ticed in industrial operations, may be
felt to the core.
An oblong piece of iron may then be
compared to a hank of parallel threads,
which will interlock with each other
when it is attempted to draw them out
lengthwise, but which will separate in a
much less regular manner when they are
drawn in the crosswise direction, at the
risk of throwing into confusion the
regularity of the original arrangement ;
forming knots and voids which must
evidently weaken the power of resist-
ance which would be possessed by the
piece under other conditions.
This effect is well exemplified by the
specimen of a railing bar, in the forma-
tion of which a rectangular bar is
transformed, in respect of its transverse
section, into a number of rectangles and
circles regularly distributed, the fibres
in the circular parts losing the parallel-
ism which is visible in the rectangular
parts. This condition would certainly
be critical, were it not that the central
part of the enlargements was afterwards
to be bored out.
The interposition of the friable silicates
between the fibres, which are more prop-
erly metallic, ought to be seriously taken
into consideration in this case as in many
THE FLOW OF SOLIDS.
329
others. At present a few of the more
characteristic facts may be noticed.
From the fact that iron wire of good
quality is capable of supporting, before
giving way, loads much greater than
ordinary iron, a manufacturer of best
scrap iron tried to work it from piles
exclusively composed of wire. A longi-
tudinal section of the bars manufactured
in this manner, having been oxidized,
reveals the filiform structure of the bar
much more clearly than any of the speci-
mens of merchant bar iron. There is
exhibited a specimen taken from an old
railing at the Conservatoire which broke
spontaneously in its place. Having a
greater proportion of the silicates in its
composition, which had been imperfectly
removed in the process of forging, this
specimen exactly reproduces an analo-
gous type.
On the contrary, when the best
Swedish iron is submitted to the same
operation it gives but the faintest indi-
cations of longitudinal strire, which
sometimes can only be produced by
taking special pains with that object.
The irons which are the most effectu-
ally purged of silicates are the best, but
the expulsion of oxides formed during
reheating on the surface of bars de-
signed to be faggoted is of great im-
portance.
The variously colored appearances
that may be raised on well-polished
sections, either by a deposit of copper,
or by the action of an acid, or, better
still, by the action of bichloride of
mercury, show clearly the arrangement
of the fibres, enabling us to trace,
through all the deformation of a piece,
the molecular displacements which, but
for that demonstration, would remain
undetermined.
The treatment by a very weak solution
of hydrochloric acid, first employed in
the Low Countries by M. de Ruth, is so
effective, that by inking the surface,
indented at the parts of least resistance
by the action of the acid, proofs may be
taken, in which the direction of the fibres
is perfectly distinguishable. By the em-
ployment of chloride of mercury, the
indentations and the fibres are much
more neatly and delicately defined.
Without reverting to the examples
given in the first paper by the author, he
will now give other instances in illustra- 1
tion of the most ordinary results from
the fibrous constitution of the metal.
On the basis of the evidence supplied
by the oxidation of polished sections of
iron, M. Le Chatelier sought to separate
the siliceous matter which envelopes the
fibres of the metal, by exposing the iron,
at a red heat, to a current of chlorine.
The iron is volatilized by this process,
and leaves a skeleton as the residue,
having the form of the original piece,
composed of extremely fine filaments,
and resembling, more than anything else,
the residue left by a match which quiet-
ly burns without inflaming, supposing
that the ash is prevented from being
pulverized.
This siliceous carcase scarcely amounts
in weight to a hundredth part of that of
the metal, but it was associated with a
certain proportion of iron, which com-
pletely disappeared in the course of the
operation.
It has been stated that these silicates
are friable when cold ; and it appears
that, with the object of diminishing the
wear of bearings, the journals of shafts
are sometimes hammered, in order to
pulverize this interposed foreign matter,
and entirely to clear it away from the
rubbing surface.
Iron, by its constitution, lends itself
much better to drawing out than to set-
ting up. The difference is well exempli-
fied in the case of a wagon axle which has
been bent while cold. If it be divided
down the center in a plane, the fine
ribbon-like appearance is clearly brought
out, and the lines are very exactly con-
centric. In the convex portion, it might
be believed that the lines were described
with compasses. In the concave portion,
on the contrary, the fibres are broken
and confused; at the same time, there
are two fractures by compression, whilst
the exterior face remains entire. Here
the texture would have been altered to a
still greater extent if the iron had been
heated for the operation, when the metal
would have been brought to a consist-
ency like that of putty.
The deformations transversely are
much better shown in a square axle four
inches square, the surface of which had
been subjected to a series of blows from
a center-punch, at intervals of 0.4 inches.
The convex portion has been extended
so much that the width has been re«
330
VAN NOSTRAND'S ENGINEERING MAGAZINE.
duced from four inches to 3.20 inches,
and the concave has, on the contrary,
been spread out to a width of five and a
half inches, in proportion as it was short-
ened in length. The simultaneousness of
such deformations is well known, and
they are the more pronounced as the
curvature is decreased. But it is specially
important to note, in this example, that
the fissures which are produced are situ-
ated only in the compressed portion,
whilst the portion principally submitted
to extension has continued perfectly
sound.
For the purpose of testing the sound-
ness of the welds in rails the rails are
frequently subjected to a series of tor-
sional stresses in two opposite directions,
which usually result in a number of
longitudinal fissures of greater or less
length, in the lines of separation of the
component bars. But, in operating on a
shaft turned out of a square bar of good
iron, much more conclusive results are
obtained. By the application of exces-
sive torsional stress, the fibres are forced
into relief, and the iron shaft absolutely
assumes the form of a rope, in which all
the exterior fibres are apparent. But
the constitution of the interior of the
shaft is still more remarkable. If a
transverse section be taken it is easy to
discover, by the agency of oxidation, the
sinuous lines which correspond to the
exterior helices, and of which the equa-
tion is precisely given by calculation,
assuming that the angle of torsion is
constant for all points of the shaft.
Supposing such a piece were to be
raised to a welding heat and forged
anew, it can scarcely be doubted that an
iron of exceptionally great resisting
power would be produced, possessing, in
some degree, the best properties of
metallic cables.
The ribbon-like constitution is never
better manifested than in iron plates, in
which it might often serve to reveal the
mode of manufacture. In iron tubes,
for example, which are manufactured
mostly in England and in France, the
regularity of the lines is such that it is
only interrupted at the weld; and a
means is afforded for ascertaining
whether the weld has been made by sim-
ple contact, or by lapping.
The same manufacture demonstrates
also the inconvenience which may attend
compression. In the section of a nut for
an iron tube, it is made evident by the
mode of striation that the hexagonal
form is produced by drawing out from a
circular section, outside as well as inside.
The layers are, at some points, separated
towards the angles, where it was neces-
sary that the section should be enlarged
by squeezing or compression.
The object to be kept in view in the
various methods of forging should be,
according to the foregoing discussion, to
dispose the fibres in the direction which
best accords with the use to which the
piece is to be applied. Mr. Haswell,
director of the workshops of the South-
ern Railway at Vienna, has attained this
object by stamping in dies piles which
are suitably prepared. The author has
had oxidized several of the pieces manu-
factured by this process for railway ser-
vice; and it is clearly manifest that,
though, here and there, the silicates oc-
cupy too much space, and are not regu-
larly diffused, the fibres are, nevertheless,
arranged in the most favorable direction
in all parts of the section.
At several other iron works, the exam-
ple of Mr. Haswell has been followed, in
the manufacture of pieces by stamping,
particularly at the iron works of Nieder-
bronn. But no doubt iron of the best
quality should be employed, in order to
derive from this method of manufacture
all the advantages which it promises.
The defects of the system are well ex-
hibited in the section of a key forged by
the stamping process from a bar of iron
doubled twice over on itself.
In all operations to which iron is to be
submitted it is important that the par-
ticular form of its constitution should be
regarded. The excellent iron plates of
Berry, which may be easily doubled, be-
cause their different layers are not suffi-
ciently susceptible of being welded, could
not, for instance, be subjected to the
American mode of punching, with a
punch which, being faced with a helicoid
surface instead of the usual flat surface,
manifestly tends to tear, at the edges of
the hole, the different parts of the same
layer.
Heat Developed in Forging. — The
study, geometrically, of the deformations
produced by forging considered under
the simplest conditions, has led, from an-
other point of view, to results which,
THE FLOW OF SOLIDS.
331
though they are not translated into defi-
nite figures, are, nevertheless, of some in-
terest, whether having regard to the de-
formations themselves, or to the calorific
phenomena by which they are accom-
panied.
When a square bar of iron is com-
pressed between two horizontal flat jaws,
equal and opposite to each other, the bar
is flattened and elongated, and the ex-
periments already made on the crushing
of metal discs afford grounds for believ-
ing that each vertical fibre of molecules
is deflected into a sinuous form, analo-
gous to the forms produced by the crush-
ing of a cylindrical block consisting of a
pile of plates. When a prism is partially
flattened the flow of the material placed
under the tool is resolved into an elonga-
tion having a curved surface, of which
the directrix is a logarithmic curve. The
equation of the curve might be given,
but it is useless to enter here into theo-
retical speculations. It will suffice,
meantime, to mention the result, and to
apply it where necessary in the course of
the discussion.
In a special example of deformation
obtained on a bar of lead by the blow of
a hammer, the distortion very much re-
sembles those which have been already
illustrated.
If each of the four faces of the prism
be divided into squares of one centimeter,
or 0.40 inches wide, the comparison of
the figures will show all the changes
which take place on one of the sides. A
small enlargement of 0.12 inches is pro-
duced on the upper face and the lower
face, but this may be neglected at first. I
Towards the middle of the depressed
portion the intermediate horizontal lines
present their convexity in contrary di- J
rections towards the center-line; and the
two verticals near the center vertical,
have, on the contrary, their maximum
separation from each other at the level I
of the center.
The two opposite squares, having a
width of 0.12 inches show respectively
two symmetrical depressions; but it is
the four squares formed by the diagonals
which manifest the most complicated
distortions. In proportion to the depres-
sion produced, the subjacent matter is
expelled both transversely and logitu-
diDally; but the second displacement is I
that which it is most important to take |
I into consideration with respect to the
j elongation to be produced, and it is the
! only displacement which can take place,
! when the piece is forged by stamping.
The elongation in the interior of the
| compressed portion being gradual, the
| depressed edge resulting from it neces-
sarily presents an inclined face. It would
theoretically take a logarithmic form, of
which the curve would unite nearly at
right angles with the original face
above, which is displaced longitudinally,
and, at the bottom of the depression,
with the depressed portion of the same
original face. This exterior side of each
of the original faces of the square is thus
drawn into a form analogous to that of
a letter Z, of which the inclined member
has been bent over in the opposite direc-
tion. The three other sides, elongated
or shortened, constitute the locality of
the greatest deformations; and it is to
this to which the whole attention should
be directed. The original lines, as well
as the resulting deformations of these
lines, are illustrated with absolute exact-
ness by a figure.
It is thus shown what takes place
under the action of the first blow of the
hammer. The second blow should cross
the first blow, when it is required to
reduce the height for the whole length
of the bar ; and an idea may be formed
of the new deformations and the re-
I straightenings which take place, by
examining the figures, in which the di-
viding lines are reproduced after each of
| three or four successive blows, one after
I the other. In spite of the care which
was taken, the deformations are not
; sufficiently symmetrical, but they are
j characteristic enough to remove any
j doubt as to the distribution of the mole-
cular action to which every part of the
mass has been submitted.
The forged bar presents extended
portions, and compressed portions, and
the result of the work would evidently
be the best possible if the vertical lines,
successively deformed in two different
directions, resumed a rectilinear arrange-
ment after each deviation. The forging
would then consist of a methodical series
of the effects of deformation, immediate-
ly followed by the effects of a corre-
sponding rectification.
Such effects become still more complex
when the bar to be forged is not sustain-
332
VAN NOSTRAND'S ENGINEERING MAGAZINE.
ed between lateral guides by which all
lateral extension is prevented. It is
evident that new deformations will be
presented under such conditions, which
will modify those which have just been
analyzed, and attention should be direct-
ed more particularly to the semicircular
protuberances which are distributed over
the length of the piece, in correspond-
ence with each blow of the hammer.
These nipples form a kind of network
produced by the forging, describing on
the lateral surface a series of lozenges
with curved sides, separated by the half
circles already mentioned.
These undulations of the surface,
which are of no importance in the geo-
metrical operation of forging, neverthe-
less deserve notice, as they indicate the
zones of maximum sliding, which are
also the zones of the maximum develop-
ment of heat ; and the author has been
enabled, by their indications, to connect
the phenomena of forging with those of
thermodynamics. It has long been
known that heat is developed by the
forging of a metal, and in some opera-
tions connected with the platinage of
steel, pieces of steel subjected to blows
rapidly delivered, may be raised to a
dark-red heat. This phenomenon does
not ordinarily take place, except in
working thin sheets ; and it will be
shown that, in working thicker pieces,
the precise situation of the greatest
development of heat can be recognized.
In a forging operation which the
author has had to conduct on a large
scale on an alloy of iridium with plati-
num, a phenomenon occurred incidentally
which engrossed his whole attention,
bearing intimately as it did on the defor-
mation of solid bodies. He may be
permitted to refer to it, though the
experiments are not yet completed ; and
it will be a source of great satisfaction
to him to make known the first results
of these experiments to an assembly of
English engineers before any publication
of them elsewhere.
Ife On the 8th of June, 1S74, the author
simply announced the main fact at the
Academy of Sciences, that when the bar
of platinum, after having been forged,
had cooled to a temperature below that
of red heat, it happened several times
that the blows of the steam-hammer
which at the same time made a local
depression in the bar and lengthened it,
also reheated the bar in the direction of
two lines inclined to each other, forming
on the sides of the piece the two diago-
nals of the depressed part ; and this
reheating was such that the metal was
in these lines fully restored to a red heat,
so that the form of these luminous zones
could be clearly distinguished. These
lines of augmented heat remained lumin-
ous for some seconds, and presented the
appearance of the two limbs of the letter
X. Under certain conditions as many
as six of these produced successively
could be counted simultaneously, follow-
ing one another according as the piece
was lifted under the hammer so as to be
gradually drawn down for a certain part
of its length.
The appearance of these luminous
traces can be explained beyond all doubt.
They were the lines of greatest sliding,
and also the zones of the greatest devel-
opment of heat — a perfectly definite
manifestation of the principles of ther-
modynamics. That the fact had not
been observed before was evidently
owing to this, that the conditions neces-
sary to be combined at the same mo-
ment had not been present under such
favorable circumstances. Iridised plat-
inum requires for its deformation a large
quantity of work to be expended upon
it. The surface takes no scale, and is
almost translucid when the metal is
brought up to a red heat. The metal
is but an indifferent conductor of heat,
and its specific heat is low. All these
are conditions which are favorable for
rendering the phenomena visible in the
forging of this metal, whilst it has
remained unobserved with all others.
Although this explanation was what
was to be expected, the author neverthe-
less proceeded to justify it by experi-
ments of a more direct character, of
which some account will now be given ;
and which constitute the chief motive,
and it may be added the chief point of
interest in this communication.
Given a bar of metal at the ordinary
temperature, if, after having coated it
with wax or with tallow on two faces, it
be subjected to a single blow of the
steam-hammer, the wax melts where, de-
pression is produced, and it is observed
that the melted wax assumes in cer-
tain cases the form of the letter X, as
THE FLOW OF SOLIDS.
333
was observed in the case of the platinum
bar. In other cases the limbs of the
cross are curved, presenting their convex
sides to each other. The heat has then
been more widely disseminated, and the
wax melted over the whole of the inter-
val by which the curves are separated.
The prism which has this melted out-
line for base, and for height the width of
the bar, represents a certain volume, and
a certain weight ; and if it be admitted
that the whole piece has been raised to
the temperature of the melted wax, the
elevation of temperature represents a
certain quantity of heat, or, in the ratio
of the mechanical equivalent, a certain
quantity of internal work which is direct-
ly exhibited by the experiment.
In comparing this work with the work
done by the fall of the hammer, a coeffi-
cient of efficiency is obtained which
amounts to not less than 70 per cent.
This value cannot be taken as final; it
depends upon the conductibility of the
metal, on the stiffness of the apparatus,
on the clearness of outline of the melted
surface. But what the author is desir-
ous to impress upon the meeting is that
here there is a return to the first methods
of Mr. Joule, and that the author's in-
vestigations of the flow of solids conduct
him to certain thermodynamic demonstra-
tions.
The following are the numerical data
for some of the experiments, together
with the illustrative figures :
(See Tables on following column.)
In the last experiment, taking as
melted the area of wax included between
the hammer and the crosses, a useful
effect of 94 per cent, is obtained.
Stamping. — The object of stamping
is to dispose the relative displacement in
given directions, in order to pass from
the primitive form, supplied direct by the
maker, to the definitive form which is
desired to be accomplished. From this
point of view, the die is a kind of chan-
nel designed to facilitate the flow of the
material, and to guide in the most suit-
able direction or directions. When it is
required to draw down by stamping a
square bar of iron, each blow of the
hammer causes transverse enlargement
as well as elongation; and the useless
enlargement is advantageously obviated
if it be prevented by the presence of the
sides of the canal. If it be well to em-
Name
Work
of
of the
Metal.
Ram.
kgm.
Iron
80
( i
90
i c
110
Copper .
60
Form of the
Impression.
Rectangular
Wide-spreading
Rectangular
Area
of
Wax
melt'd
Thick-
ness
of the
Forg-
ing.
sq. ct.
1.45
1.50
2.20
1.75
cent.
2.5
2.5
2.5
2.0
Volume
of the
Corre-
spondi'g
Prism.
cu. cent.
3.63
3.75
5.50
3.50
Correspond-
ing No. of
Heat-Units
(Heating to
50 deg. C).
0.1498
0.1547
0.2269
0.1329
Jiiquivalent
Work, at the
Rate of 435
kgm. per
Caloric.
kgm.
63.72
69 79
96.44
56.48
Proportion
Percentage
of Total
Work con-
verted into
Heat.
0.796
0.731
0.877
0.942
ploy the stamp in simply drawing down
a bar, how much more indispensable is it
when the variation of form is more com-
plex? The simple idea of flow supplies
material for forming a rational judgment
on the successive dispositions of the
stamps required for the intermediate
operations; and also on the adjustment
of the sections of rolls, which are but
circular stamps or moulds, by means of
which iron is drawn out.
That all these phenomena are but va-
rious forms of flow, of which in most
cases the circumstances can be antici-
pated, may be shown by other experi-
ments which will now be described.
The most characteristic of these ex-
periments is, perhaps, the following :
Having completely effaced the reverse
in relief of a piece of money, place the
flat surface on a sheet of lead, and flat-
ten the second face in the stamping press.
The whole relief of this face will be pro-
duced on the face which had been re-
duced to flatness; and the design of this
relief will even be imprinted on the lead.
This effect is explained by the circum-
stance that each vertical thread or fibre
of molecules, being separately com-
pressed in the direction of its length,
flows, when struck, with greater facility
into the lead than into the other parts
of the piece. The saliencies, as repro-
duced, are less, no doubt than in the or-
334
van nostrand's engineering magazine.
iginal relief, whilst the more delicate
features are partially obliterated, but the
general effect is reproduced and it is ap-
parent that the flow takes place in the
direction of the depth, which is also the
direction of least resistance.
On the reverse of the sheet of lead,
which has necessarily been reduced in
thickness by the effect of the imprint,
the image will be found repeated in a
more confused manner, and it may be
distinguished by a peculiar tint which
indicates a well - defined geometrical
transformation; the lead having flowed
in a horizontal direction, as the only way
of escape when its surface was depressed.
This amplification or enlargement takes
place in the proportion of 22 to 13, when
the plate of lead was J inch thick.
An entirely different effect is produced
when a medal is struck. The blank piece
having been placed in the matrix, the
portions which are not to be raised in re-
lief by the action of the press are re-
duced in thickness, for the benefit of the
neighboring portions which are raised;
the metal literally flowing, in radial di-
rections, from the hollows to the reliefs
by which they are surrounded.
If the medal has only an engraved
face, it maybe made up of several blanks
of equal thickness superposed. The same
mode of distribution of the molecules
takes place, and is manifested by succes-
sive imprinting at each face, in which
the final relief is more or less obliterated.
It is so clearly a manifestation of flow
that takes place under these conditions,
that if the bottom of the matrix be hol-
lowed out at the center, then, the mate-
rial which converges from the circum-
ference exciting a pressure towards the
center, the central portion of the blank
is driven towards the orifice, where it
forms a very regularly shaped boss; ad-
mitting of the transformation of a relief,
executed on a plane, into a similar relief
on a surface which has become very con-
vex or very concave, according as the
design pertains to the upper or the lower
face of the blank.
To an analogous cause, the presence of
scars sometimes observed on medals
highly relieved, is to be attributed; these
scars being produced simply by the junc-
tion, during the later strokes, of the
edges of the bosses which are formed by
the earlier strokes.
When the medal is relieved on both
faces, if it be made up of several plates
superposed, it is interesting to remark
the successive developments and efface-
ments of the images on both sides of the
plates; mingling and merging in each
other in a singular manner.
Rules cannot yet be formulated for
the best forms of the grooves of rolls;
but it may be accepted that they should
be shaped in such a manner as to utilize
as far as possible the natural flow of the
metal in the direction of the pressures
applied to it.
It has been shown that, when a bar is
to be drawn out, it is best to prevent any
enlargement of it laterally, and to facili-
tate the longitudinal flow; the die
should, therefore, be carefully gauged,
short, and opened out in the direction of
the length.
It has been seen, also, that in stamping
a disc, it may be useful to make use of
centripetal compression. Each mode of
action has thus its own mode of deforma-
tion of which it is necessary to know how
to take advantage. The following is a
very remarkable instance : Given a disc
of lead 4 inches in diameter and ^ inch
thick; if it be pressed, in the stamping
machine, for a diameter of 2^ inches at
the center, the thinning of this central
portion is only effected by the flow of
the material outwards; and this flow is
exactly symmetrical, when the centering
is perfect. The exterior border is devel-
oped in the form of a tulip. By such
means, without the employment of a
matrix, geometrical forms of a perfectly
definite character may be produced,
which may be useful in some cases.
This general disposition of material
had been long since observed by MM.
Piabert and Morin, in the course of their
experiments in drawing out blocks of
clay. Around the orifice of entry the
clay was thrown out in the form of acan-
thus leaves, and the same development
is to be observed in the displacements
which take place when projectiles are
discharged against armor plates. The
metal displaced by the projectile is
driven forward in flakes or strata more
or less involved and dislocated, which
have, nevertheless, a striking family
likeness to the dispositions previously
noticed.
The geometrical condition of the de-
THE FLOW OF SOLIDS.
335
velopment in tulipform of the plate of
lead may be very simply explained. The
border of the plate, which makes an
effort to retain unaltered its diameter
and its thickness, continues to be attach-
ed to the central portion, the gradual
crushing of which throws out rings
which are successively thinner and
thinner. These rings have, therefore, at
each ingtant, a given thickness, and by
their succession they necessarily form a
surface of revolution, which is accurately
calculable, on the hypothesis, which is
perfectly justifiable, that the volume is
constant.
The conditions of such development
may be modified by the employment of
casings of various forms; but attention
will be confined to the case of a concen-
tric casing so disposed as to prevent any
increase of diameter.
Eight discs of lead 1^ inches in diame-
ter having been placed in a cylinder, a
piston of 1.20 inches in diameter is
placed upon the pile formed by these
plates. Since the material can only
escape from the compressive action by
the annular space comprised between the
piston and the cylinder, it ultimately as-
sumes the form of a sort of tumbler, of
which the height is extended to the
length of the piston, even beyond the
length of the cylinder. The thickness
of the tumbler, 0.15 inches, would have
been more regular if but one disc of lead,
or of tin, had been employed. But the
mode of distribution of the layers in the
thickness of the tumbler is in itself a
useful subject for consideration. The
uppermost plate has been developed, al-
most in one piece, to the upper edge of
the tumbler, being connected by a con-
tinuous supplementary party which be-
comes gradually thinner until it reaches
the foot of the tumbler. The other
plates are also developed, in a parallel
direction, supported by the sides of the
cylinder, for a length which may be sub-
mitted to the same kind of calculation as
that of the plates of the concentric jets.
It is the same mode of deformation ap-
plied, in the present case, to an annular
jet; and the complete analogy between
the formulas which give expression to
their relations is not one of the least re-
markable facts in these transformations.
This method has for several years
been adopted in industrial operations,
under conditions of precision which are
truly astonishing, in which a vertical and
cylindrical jet, 12 inches high, is manu-
factured from a sheet of tin perfectly
smooth and of uniform thickness. In
the finest specimens of that size, the
ends of the tube, which are pared after
having been struck, do not show any
irregularity exceeding ^ inch in height,
even though the cylindrical envelop has
been suppressed for the whole height.
The substance driven out in the form
of a ring, the thickness of which is
measured by the difference between the
radius of the punch and that of the
matrix, is naturally disposed to form a
thin cylinder, the several elements of
which slide with equal facility upon the
perfectly polished surface of the punch.
A thousand examples of similar sur-
prises may be found in industrial process-
es ; but this instance, amongst them all,
definitively sanctions the expression by
which the author believes he is author-
ized to designate the results of his
researches. The flow of solids is now
recognized in science; much more will
it be accepted by the members, who are
witnesses every day of the processes
which are based upon it, as the true
expression of the best ascertained facts.
Planing. — Of the various operations
which have been described above, that
of punching is the only one which has
had for its object the dividing of a solid
body, and forming two entirely separate
parts — the burr and the punched block.
The block is augmented by compression
of a portion of the matter which consti-
tuted the cylinder which would have
been simply pushed out by the punch,
supposing that the cylinder could have
slipped out without giving rise to other
phenomena. The burr is reduced by the
same amount.
Cutting or shearing does not really take
place until the moment when the burr,
in consequence of lateral flow, has been
reduced to its height. It has been proved
that from this moment the resistance op-
posed to shearing is actually proportion-
al to the area of the zone of shearing.
The co-efficient of resistance applicable
to this separation is no other than the
co-efficient of resistance of fluidity; or
what amounts to the same thing, the co-
efficient of resistance to rupture; so that
we are now put in possession of a cer-
336
VAN nostkand's engineeking magazine.
tain formula, applicable equally to cir-
cular shearing by the action of the
punch, and to rectilinear shearing by the
shear blade or by the turning tool.
In each case one of the parts of the
piece slides upon the other part, produc-
ing at the two sides in contact a draw-
ing out of the successive layers, which
are bent over in the direction of the
length of the shorn surface, in thin
shreds, like those produced by the
punch. The separation only really takes
place at the moment when these shreds
are drawn to their extreme limit of ten-
uity.
This characteristic of the separated
surfaces is met with in planing, although
the principal circumstances may here be
entirely different; not less remarkable,
however.
The principal difference consists in
this, that the chief compression takes
place, not in the solid mass as before, but
in the cutting which is detached by the
tool, which, as it forms the exterior por-
tion, opposes to the flow the least resist-
ance. If the cutting be compared with
the space which it occupied in the block
before separation, it is easily observed
that it is at the same time considerably
shortened, and that, consequently, its
thickness has been augmented in the in-
verse of the shortening.
The leading fact in planing is very
well exemplified in the turning from the
wheel-tyre of a locomotive comprising a
cutting for the rivets. These are repre-
sented as of an elliptical section, 1| by fa
inches, showing that the reduction in
length affected by the action of planing
was in the ratio of 10 to 28, or 0.36.
This co-efficient of reduction is still
much greater than it is in many other
circumstances; for the thinnest cuttings,
the co-efficient is occasionally as low as
0.10.
In another instance, a cutting planed
off transversely from a double headed
rail, the height has not been altered, but
the width has been reduced nearly in the
same proportion as in the first example.
Another characteristic of cuttings pro-
duced by planing is that the surface of
the cutting which rises from contact
with the cutting-tool is always smooth,
and is developed geometrically. That
surface, in fact, is moulded on the tool
during the process of deformation, and
slides upon it in such a manner as to roll
itself up in the form of a cone or of a
cylinder. At this moment, above all
others, the plasticity of the metal is
brought into play; and if the original
form of the cutting should interpose too
serious obstacles to this development, it
tears or splits according to the direction
of the generating surfaces of contact,
still responding to the geometrical con-
dition first referred to. It is well to
avoid,such rents as much as possible, for
evidently they cannot be produced with-
out the expenditure of additional power.
Such loss of power must take place,
especially where it is required to reduce
a curved surface at one cut, of great
breadth. An example of such fissures is
shown on about a third of the width of
another cutting from a tyre; but those
of the opposite edge are attributable
really to a greater reduction of the
length of the thinner edge in the process
of planing.
The other face of the cuttings is
always rugged and wrinkled with fiss-
ures or with transverse ridges, of very
variable aspect, according as the metal
is more ductile and the cutting is thick-
er. For the greater thicknesses both iron
and steel present on that surface a mul-
titude of inclined ridges partly covering
one another ; and of which the incline is
still better defined where complete separ-
ation has been produced.
These scales have been drawn just as
they appear under the microscope, on a
cutting of Bessemer steel. Nothing can
show better than their general inclina-
tion the sliding that may be produced in
planing, in consequence of the compres-
sion which is produced in front of the
tool before the cutting is completely
detached from the block.
In the greater number of cases the
turning when long enough winds up into
a helicoidal form, as may be seen on the
cutting, of which the rugged face has
just been shown.
The inclination of the spirals depends
upon that of the cutting edge of the
tool, and their diameter upon the thick-
ness of the cutting; the diameter dimin-
ishing with the percentage of reduction.
It is thus that, in turning in the lathe a
piece which is very slightly eccentric,
the result is a number of parts of which
the diameters are alternately greater
THE FLOW OF SOLIDS.
337
and less. The demonstration afforded by
this single specimen is quite complete.
Without seeking to draw any conclu-
sions from the study of these deforma-
tions with respect to the best form of
tools for each of them, it follows clearly
from the foregoing discussion that the
work required for any cutting action
whatever is expended in friction and in
deformation by compression. The work
of friction should augment with the
number of cuts, and as the shortening is
greater for the liner cuts the molecular
work expended should be greater. It
follows, therefore, that it it is most ad-
vantageous to make deep cuts, but, of
course, this mode of action demands
more powerful tools and better founda-
tions. It is in this direction, it appears,
that the most recent progress in the
manufacture of tools has been effected.
The different modes of cutting, recti-
linear or circular, are applicable chiefly
to flat surfaces and to cylindrical sur-
faces.
Flat surfaces are cut in the planing
machine or in the lathe, and under most
circumstances the two kinds of cuttings
are almost identical in appearance — that
of a cylinder formed of spirals more or
less close, sometimes even in juxtaposi-
tion; but for this combination, it is nec-
essary that the two edges of the cutting
should have been equally reduced, that
is, that they should be of the same thick-
ness. If it were otherwise the spirals
would become conical; and such of these
as appear to be most characteristic will
now be described.
The cutting obtained in mortising, by
means of a straight tool, is absolutely
cylindrical.
When the tool cuts out, in this man-
ner, a rectangular groove, the material is
compressed without any lateral devia-
tion. If the cutting is of great thick-
ness, it is triangular, and the smooth
surface is formed by the combination of
the three faces at which the separation
takes place, the direction in which
crumpling takes place being the same as
in all ordinary cuttings. The triangular
form is the result of the compression
being greater toward the middle line.
To aid in forming an opinion on this
point two blocks were placed side by
side, which were planed at the same
time, in the line of junction of the pieces.
Vol. XIX.— No. 4—22
Two distinct horns were formed, which
parted symmetrically from one another;
each half-cutting following the law of
shortening by which it was bound to as-
sume a form concave towards the side
which was held by its attachment to the
block.
Having made a similar experiment in
lead, the parallel and equidistant lines
that were drawn upon the block before it
was cut could be traced on the cutting,
and they afforded the means of measur-
ing exactly the average percentage of
reduction, and the mode of contortion of
these transverse lines, which assumed
successively the same inclinations as they
lay one upon another at intervals, of
which the percentage of reduction varied
from 0.10 to 0.30.
The cuttings from a lathe, when they
were produced from an annular groove,
by means of a straight tool, assumed ex-
actly the same forms. For example, a
cutting from a groove in what is called
the Swedish piston is a continuous rib-
bon rolled up as on a bobbin, with the
greatest regularity, and of great length,
without a rent.
When turnings take the form of a
helix, the small lateral displacement of
the piece is not large enough to give to
the ribbon a different character to that
from a planing machine, when, for in-
stance, it is required to turn a shaft to a
uniform diameter, and it is then easy,
with good metal, to produce cuttings of
great length. But, when it is required
to turn the end of the shaft or of any
cylinder whatever, the cutting follows a
special course. If the tool be large in
proportion to the diameter of the rings
or circles on which it is acting, the dif-
ference of diameter between the two
edges of the cutting makes itself felt in
the cutting, which assumes the form of a
helicoidal surface, with inclined genera-
ting lines, of which the directrices are
two helices of the same pitch but of dif-
ferent diameters. This universal geo-
metrical character, moreover, is mani-
fested in special ways according to the
width of the ribbon and the interior di-
ameter of the ring. In this way three
horns may be obtained, encased one in
the other, if the cutting edge of the tool
be radial. Successive spirals foul each
other when the direction of the cutting
edge is a little inclined. The inner helix
338
VAN NOSTRAND'S ENGINEERING MAGAZINE.
is replaced by a straight edge when the
tool cuts right to the center of the' face.
Notwithstanding these differences of
detail, the same rules prevail : a greater
or less reduction or shortening, according
to the thickness of the cutting ; a less
reduction of length at the thicker edge
of the cutting; a smooth surface of sep-
aration, which always forms a develop-
able surface ; a rugged reverse face
ridged as if waves of metal had been
successively projected there ; in fact) all
the circumstances of a transverse flow of
material — setting apart the secondary
circumstances, of transformation of the
prism of metal from which the cutting is
produced by augmentation of thickness
and corresponding reduction of length.
The author endeavored to represent,
by a diagram, the triangular cutting
which would be formed by planing from
the edge of a block of metal a square
prism, by means of a tool having two
cutting edges, and of which the flat front
is itself placed symmetrically. The
effect of the diagram, constructed on the
assumption of a percentage of 0.30, is
exactly reproduced by the model in
relief. In agreement with the foregoing
discussion and with the facts, it may be
observed how the .prism which is on the
point of being separated from the block
swells up by compression, commencing
at a certain zone of fluidity, of limited
length, in advance of the tool ; and
how, when this compression has arrived
geometrically at the maximum which
could be sustained by the material, the
cutting is detached from the mass to be
subjected to the action of the face of the
tool, upon which it slides, and which
forces it to assume its ultimate form.
Considerable as these modifications
may appear, they are absolutely in
accordance with the facts. They have
been produced by the author, on lead as
well as on the hard metals, under condi-
tions which were exactly proportional
to those which are represented by the
model.
The finest specimens of this triangular
transformation of cuttings that have
come under the author's observation, are
produced by a mortising tool. They are
not less than -^ inches thick, and the
rolling up of the metal could only be
effected with the accompaniment of deep
fissures in the lateral edges. The upper
edge, on the contrary, is much more
minutely serrated, one of the lateral
faces is plaited for its whole length, evi-
dence of the compression of the material;
whilst the other face, with its oblique
fissures, shows still better the sliding by
means of which the compression takes
effect.
There is a still smaller cutting which
presents exactly the same characteristics.
It is the author's opinion, that for the
construction of the best machine tools,
with the most suitable thickness of cuts,
the minute examination of the cuttings
is of the greatest importance ; and that
by the same means, the surest evidence
may be derived with respect to the quali-
ties and homogeneity of the metal.
Time does not permit of more than a
passing reference to certain deformations
which recall to mind, with a surprising
degree of exactness, the constitution of
certain rocks, with their dislocations. A
few experiments of this kind were made
by the author in conjunction with M.
Daubree, from which the latter gen-
tleman quite recently derived an expla-
nation of a number of geological
phenomena. The results of these inqui-
ries would no doubt possess some interest
for the members, but the author was
desirous chiefly to lay before them such
results of his investigations as followed
in natural sequence upon the substance
of the communication already made in
1867.
The idea of the flow of solids is, of all
the modes of regarding their deforma-
tion, perhaps the one which most truly
interprets all the phenomena of molecular
mechanics, and of the internal constitu-
tion of bodies, which underlie the various
industrial operations.
Mr. Samuel Shaepe has promised to
give £500 towards the building of the
North Wing of University College, Lon-
don, so soon as the Council are prepared
to begin the work. It is expected that
this liberal donation, together with oth-
ers which have been received, will enable
the building to be very shortly com-
menced. A sum of £50,000 in all will,
however, be required to complete the
extensions which are immediately con-
templated.
THE ACTION OF KAILWAY BEAKES.
339
THE ACTION OF RAILWAY BRAKES.
From "The Engineer."
On Monday morning Captain Douglas
Galton and Mr. Westinghouse resumed
their inquiry into the action of railway
brakes, which had been interrupted for a
short time to enable certain alterations
to be made in the construction of the re-
cording apparatus in the experimental
van. It will be remembered that the in-
quiry began on May 27th, and we illus-
trated the experimental van and com-
mented on the results obtained in our
impressions for May 31st and June 7th
and 28th. All the alterations since made
in the van refer to matters of detail,
their effect being that the diagrams given
by the recording apparatus are clearer
and more perfectly trustworthy than be-
fore. Two ends of two carrying springs
have been attached to levers which act
on a water-pressure diaphragm, and by
means of a Richards indicator, record the
action of these springs. The system of
scaling the diagrams has also been modi-
fied, but with these exceptions, what we
have already said in the way of descrip-
tion will apply to all that follows. It
may be worth while for the sake of ren-
dering matters clear, however, to explain
that six indicators are used to record —
(1) The angular or tangential strain on
the brake blocks; (2) the motion of the
carrying springs of the van ; (3) the force
applying the blocks to the wheels; (4)
the pull on the draw-bar of the van; (5)
the speed of the van, the motion of the
indicator being derived from the leading
wheels to which only the brake is applied;
while (6) is a somewhat similar indicator
driven by a belt from the unbraked
wheels. There are, besides, two Stroud-
ley speed indicators in the van, employed
to check the accuracy of the Westing-
house instruments just named.
On Monday morning the van drawn by
the " Grosvenor " left Brighton station
and ran to Hastings and back, several
experiments being made on the road.
Unfortunately, however, a portion of the
brake rigging gave way during the ex-
periments, and brought them to a close.
On Tuesday morning, with new and
stronger rigging, the experiments were
resumed, and continued on Wednesday.
We may be excused for not going
minutely into the investigation of the
results obtained, when we state that on
the first day alone more than 120 dia-
grams were obtained, which will have to
be compared and arranged and measured
before definite results can be made pub-
lic. This is a work of some time. We
may, however, with advantage, indicate
the nature of such phenomena as appear
most worthy of attention.
The first point claiming attention is the
failure of the brake rigging. This con-
sists of a Y-shaped frame, the two limbs
of the Y being welded to a stout trans-
verse rod, the ends of which are pro-
longed beyond the limbs of the Y far
enough to pass through the brake shoes.
The single leg of the Y is connected by
a system of levers with the piston rod of
the air cylinder, and when the brake is
applied the whole Y frame is put in ten-
sion, with the exception of the transverse
bar, which is in compression. The diag-
onal bars or limbs of the Y are of -J in.
round iron; the transverse bar is of 1^ in.
round iron. This bar gave way by bend-
ing in the middle on Monday. It was
replaced by a much stronger rigging on
Tuesday. The strain put on each brake
block is precisely 100 times the pressure
per square inch in the air cylinder when
the brake is applied. This cylinder is 8
in. diameter, and the piston is conse-
quently 50 square inches in area. Now
the highest air pressure used during the
trials was 95 lbs. on the square inch in
the brake cylinder. This drove each
block against the wheel rim with a force
of 9,500 lbs., and under the strain thus
brought to bear on the tackle, the hori-
zontal extension rod gave way, as we
have said, by bending. But this, like all
the similar tackle used by Mr. Stroudley,
had been tested in the shops with a press-
ure of 120 lbs. on the square inch, or
12,000 lbs. on each shoe, and had with-
stood the strain perfectly. The lesson to
be drawn is that unless all the conditions
under which any member of a machine
has to operate are taken into account, the
results of tests of endurance cannot be
regarded as trustworthy. In the shop
340
VAN nostrand's engineering magazine.
the brake rigging while under strain was
not subjected to any violent jarring
action ; on the road the vibration set up
in the metal was active, and promoted a
rearrangement of the molecules of the
bar. Bearing this in consideration, it is
by no means to be regretted that the
rigging gave way. The experience ob-
tained is worth a good deal, and admits
of very extended application. It illus-
trates the prudence of Lloyd's rule that
when chains are being tested by tension
they should also be struck sharply with
a hammer; and it throws some light on
certain so-called mysterious failures of
structures to do the duty expected of
them, and performed by them when
originally tried in the maker's yard. We
may here add that tackle of the kind
which gave way has hitherto been found
quite strong enough in regular practice.
The results obtained when the brake
was applied under varying conditions,
were exceedingly curious. We have al-
ready explained that when a wheel skids
two things take place — (1) The angular
strain on the brake shoes is enormously
augmented for a moment; and (2) it then
sinks to much less than it is when the
wheel is revolving with the shoes pressed
hard against it. In other words, broadly
speaking, it would seem that the resist-
ance to forward motion offered by a
wheel skidding on a rail, may be much
less than half that offered by the same
wheel while still revolving at full speed,
the brakes being in action. This fact
was brought out very prominently on
Monday and Tuesday. To test the point
in another way, a few special experiments
were made. Matters are now so arranged
in the van that the pressure in the brake
cylinder can be determined with the
greatest nicety. In the twenty-second
experiment the speed of the van being
forty miles an hour, the wheels could not
be skidded with a pressure of 60 lbs., or
6,000 lbs. on each brake block. But in
the twenty-third experiment, although
the speed was forty-two miles an hour,
the wheels skidded. The speed remain-
ing about the same, the pressure was
gradually reduced, but the wheels would
not begin to revolve again until it fell to
7 lbs. on the square inch. From this
about 2 lbs. must be deducted for the
pressure required to overcome the resist-
ance of the spring which takes the brake
off, leaving a net pressure of 5 lbs. In
other words, although 6,000 lbs. on each
block, or 24,000 lbs. for the pair of
wheels was required to skid them, 2,000
lbs., or one-twelfth of the amount, sufficed
to keep them skidded. It must not be
supposed, however, that this represented
the diminution of resistance of a skidded
as compared to an unskidded pair of
wheels; on the contrary, the draw-bar
diagram shows that the resistance of the
skidded was somewhere about one-third,
instead of being only one-twelfth that of
the unskidded but braked wheels. The
blocks used in this case were of cast iron,
12 in. long. Those used on Tuesday
were also of cast iron, but 16 in. long.
With these last, in one experiment a
pressure of 70 lbs. to the square inch was
required to skid the wheels, but only 6
lbs. sufficed to keep them skidded. At a
velocity of four miles an hour skidding
was produced by a pressure of but 40 lbs.
At high velocities, such as fifty to sixty
miles an hour, a pressure of less than 90
lbs. would not produce skidding. It is
worth notice that, no matter what the
speed of the train, a pressure of 6 lbs. to
8 lbs. kept the wheels from revolving.
This appears to demolish the theory that
at high velocities the coefficient of fric-
tion between wheel and rail is less than
at low velocities. If this theory were
correct, then when the train was running
slowly a much greater pressure would be
needed to keep the wheels from turning
than would suffice at high speeds; but so
far as the inquiry has as yet proceeded,
not a scrap of direct evidence to this
effect has been obtained.
There is but one way of explaining
the various anomalies presented by the
results of these experiments. They are
in a very large proportion due to the in-
ertia and momentum of the wheels. To
elucidate this point a little, we give the
following figures: — The weight of the
brake van is 8 tons 2 cwt. 2 qr., or, with
fourteen passengers, nearly 20,400 lbs.
These figures are not precisely accurate,
but near enough for our purpose at
present. About one-half this weight
was on the braked wheels, which invaria-
bly went first. When the brakes were
applied, the springs deflected § in.,
showing an augmentation in weight, the
precise amount of which has not yet
been calculated, and which was due to
THE ACTION OF RAILWAY BEAKES.
341
causes which are too obvious to need ex"
planation. We shall assume that the
load under these conditions on the braked
wheels was 11,000 lbs.; but in order to
stop these wheels from revolving at
thirty miles an hour, or 44 ft. per second,
a pressure of 60 lbs. was required. This
represents 6,000 lbs. on each brake block,
or 24,000 lbs. in all; but the wheels
pressed on the rail with a force of 11,000
lbs., or but eleven-twenty-fourths of the
force with which the brakes were ap-
plied to the wheels. If the matter ended
here, we should be justified in assuming
that the coefficient of friction between
wheel and rail was more than twice as
great as the coefficient of friction between
wheel and brake block. But the wheels
when once skidded could be kept skid-
ded apparently at any speed, slow or fast,
by forcing the brake blocks against
them with a force of 6,000 pounds only,
or less than half the insistant weight ;
consequently on this basis we would
have reason to assume that the co-effi-
cient of friction between wheel and
blocks was much greater than that be-
tween wheel and rail. These two as-
sumptions are contradictory, incompati-
ble, and yet each is justified by the ex-
periments. Both assumptions are, how-
ever, vitiated by neglecting the mass of
the wheel. Before the wheel can be
stopped the work stored in it must be
taken out of it. Let us represent this
by x, and the resistance proper to the
co-efficient of friction between wheel and
rail by y. Then the duty to be per-
formed by the brake in stopping the revo-
lution of the wheel must equal x + y.
Again, to put the wheel in motion after
it has stopped, y must reproduce x.
Let the resistance due to the co-efficient
of friction between the wheel and block
be represented by z. Then y must equal
x + z, or the wheels will not begin to
revolve with the brake on. We have
here purposely omitted all reference to
the important part played by time in this
matter, as it will suffice for our present
purpose to call attention clearly to the
fact that momentum and inertia must
be taken into consideration. To show
how important a part both play in the
matter, it will be enough to say that the
revolving mass of each wheel of the van
is as nearly as may be equal to 450
pounds moving at the speed of the train.
Thus at thirty miles an hour, or 44 feet
per second, the vis viva of each wheel
is not less than 13,500 foot-pounds, and
to stop such a wheel in one second
would require a tangential force of 950
pounds; or assuming the co-efficient of
friction between block and tire to be 0.1,
then a single block would have to be
pressed against the wheel with a force
of 9,500 pounds, and this, be it observed,
withont taking any account of the fric-
tion between rail and wheel tending to
keep the latter in motion. In like man-
ner, if the speed be sixty miles an hour,
or 88 feet per second, then the vis viva
of the wheel will be nearly 54,000 foot-
pounds or 24 loot-tons; and to stop such
a wheel in one second, or 88 feet, would
require a force of, in round numbers,
6,000 pounds, or a brake-block pressure
of 60,000 pounds. It is hardly necessary
to say that no brake exists which will
produce skidding under such conditions
in one second; and although apparently
skidding does take place suddenly and
with a jerk, yet it is certain that nothing
like instantaneous action ever occurs.
Again, when the wheel has been skidded,
a force of 6,000 pounds would have to be
applied to its circumference to cause it
to resume motion at the rate of 88 feet
per second within a distance of 88 feet;
and it was abundantly proved by obser-
vation in the van on Monday and Tues-
day, that if the pressure upon the brake
is taken off altogether, the wheels will
continue to skid for some moments, and
that they resume their velocity slowly.
It is well known, indeed to engine dri-
vers that tender wheels obstinately
refuse to revolve when skidded at high
speeds for a quite preceptable time after
the brake has been taken off.
It will be seen, then, that the task
which Captain Galton has before him is
no light one. Certain conclusions, hav-
ing a direct practical bearing, can be
drawn easily enough; but neither Cap-
tain Galton nor Mr. Westinghouse is
likely to be satisfied with this. The
London & Brighton Railway Company
have, with the utmost liberality, placed
unexampled facilities for making ex-
periments at the disposal of Captain
Galton and Mr. Westinghouse, and the
latter gentleman has prepared an appa-
ratus which will deal with any brake,
air or vacuum. Facts are being obtain-
342
VAN NOSTRAND'S ENGINEERING MAGAZINE.
ed by the hundred, and it rests with
Captain Galton to reduce these facts to
a condition which will render them ex-
tremely valuable to the man of pure
science, as well as to the engineer.
Nothing, however, can be learned con-
cerning the laws of friction unless the
influence of the vis viva and inertia of
the revolving wheels is carefully calcu-
lated for every experiment.
THE RIVER THAMES.
From "Engineering."
The Thames Conservancy and the
Metropolitan Board of Works have,
during the last twelve months, been
placed in diametrical opposition in re-
gard to their views of the cause of the
pollution of the Thames, and each Board
has published a report casting the blame
on the other. These reports have been
criticised by engineers, chemists, and
others, and the simple result has been
that the public have been left in a fog
of Egyptian darkness as to whom is due
the fact that about 20 miles of the river
is rapidly approaching a state equal to,
if not physiologically worse, than that
which we observed in 1848-49 (cholera
years) and in 1855-56, when the Thames
was literally no better than a foul stink-
ing ditch. It was from this latter cir-
cumstance— the abomination of sanitary
desolation — that the main drainage
scheme had its origin, and we regret
to add in some senses its failure, so
far as recent experience goes.
Again, the present year has afforded
a repetition of evils that are periodic.
For several years past the summer tem-
perature has been comparatively low.
During the last month it has been liter-
ally tropical, ranging from 75 deg. to 85
deg. Fahr. in the shade. Hence, as we
shall presently show, the Thames now
presents appearances that cannot be re-
garded without serious apprehension.
If our conclusions be true the condition
of the river is at least serious. Of this
our readers may, without any pretension
to engineering, chemical, or other pro-
fessional knowledge, easily judge for
themselves, and to assist them in so
doing the following brief account of the
observations, experiments, &c, that
have been made, and the mode of
conducting them, may be of advantage.
Our observations for the present year
were commenced on the 13th of April.
On that day the Thames from London
Bridge to North Woolwich presented
very much the appearance of a farm-
yard pond. Between Blackwall and
Woolwich, the amount of confervoid
matter, floating in the river, was so
great that its green color could scarcely
escape the attention of any one having
occasion to pass down the stream. This
color of course indicated the presence of
an immense amount of vegetable germs
in suspension. Subsequently it became
evident that the river was loaded with
these organisms, and on July 22, when
the last of these observations were taken,
the water at ebb, from Blackwall to the
south shore upward of Purfleet, presented
a color of a dark olive-green, with a
" sweet " fetid smell common on all the
marshes of the Thames and Lea, at the
time the weeds, &c, decay, especially
during a warm August and September.
As a rule during the three months
above mentioned, samples were gathered
from Westminster to North Woolwich,
and occasionally to Gravesend, as the
tide ebbed, so that the end of the low
water could be reached at the last sta-
tion, below London Bridge. None were
taken at an interval less than three or
four days after a rainfall, it being desir-
able that the river should be seen in its
normal state. Here it may be remarked,
that a heavy rainfall, as on June 23rd,
entirely destroys what we may call nor-
mality of the stream, owing to the large
amount of oxygen brought into the river
in solution. From neglect of this pre-
caution has arisen the absurd idea that
sewage, running for a few miles, be-
comes oxidised under all circumstances.
It may, after a heavy rainfall, for reasons
already assigned. We haye known for
example the Learn, which runs through
THE KIVER THAMES.
343
Leamington, and shortly below joins the
Avon, to be wonderfully improved after
a rainfall, which increased the sewage to
1,500,000 gallons per day from 450,000
gallons, the latter quantity being at the
time we refer to about the daily average.
These and other sources of error were
carefully avoided in our examination.
Our space will not permit us to give
more than a general summary of the
various observations made during this
period of three months, but those made
on July 22nd may be taken as a normal
type. At 9 a.m. to 10 a.m. the river
presented an appearance of a dark olive
tint mixed with brown, between London
Bridge and Blackwall. Between Green-
wich and Blackwall there were frequent
issues of suspended matter, apparently
from the escape of gas from the bed of
the river, which produced circular areas
of increased suspended matters, so dense
as to completely hide from observation
the bottom of a glass 3 inches below the
surface. Beyond Blackwall to Barking
the smell of the water was of that pecu-
liar decomposed vegetable character al-
ready alluded to, varied by the stench
of nitrous acid and glue or manure pre-
parations from the north bank. This was
so offensive as to stir up the attention of
some children, who adopted the time-
honored plan of keeping the smell from
their noses. The wind was N.N.E. At
the Crossness outfall of the South Lon-
don sewage, there was a considerable
deposit of sewage matter on the bank,
and on the upper part of the bank the
green deposit showed signs of vegetable
matter, arising from the mixture of sea
and fresh water.
At this point and eastwards the water
in mid-channel was a vegetable green
color, with a strong bilge-water smell.
A mile below, the stench of some works,
dealing with boiling animal matter, was
most offensive. A little further below
and near Price's wharf was a long sew-
age deposit; the same occurred near, but
west of Erith. Below Erith the water
became worse in color in mid-channel,
with deposit of sewage matter on the
south shore, especially in hollows. At
Purfleet the river presented an appear-
ance very commonly to be seen at Dum-
barton on the Clyde, where sewage and
sea water freely mix. The south shore
near Greenhithe presented sewage de- [
posit. Here it may be remarked that a
specimen of water taken from mid-chan-
nel was perfectly free from sea-salt
taste, a fact indicating that the sewage,
&c, had, with the ebbing tide, traveled
so far on its journey toioards the sea, but,
as we shall see, not into it.
At the turn of the tide at Gravesend,
about noon, as indicated by a small boat
presenting its stem eastwards, samples
were taken of the surface water. These
could only be compared, as regards sus-
pended matter, with the worst specimens
of sewage that might be drawn on or-
dinary occasions from London sewers.
When shaken the suspended matter os-
cillated in the glass vessel, as if immersed
in a viscid fluid, showing signs of the
presence of sewage that could not be
mistaken by an experienced eye. As
the larger vessels (200 tons and upwards)
turned stem to sea, fresh samples were
taken from shore to mid-channel, with
the same result. The water was brack-
ish to the taste, indicating that the out-
ward flow of the sewage to the sea had
been arrested, In other words the me-
tropolitan sewage was being driven back
to London, with the addition of sea-wa-
ter, which of course makes bad worse.
Here, by way of parenthesis, we may
remark (as we have already frequently
done) on the danger of mixing sewage
with sea-water. We have, in previous
volumes, drawn attention to the experi-
ment of Professor Daniell on the effects
of mixing land drainage water with sea-
water on the coast of Africa, off the
Niger, &c, particulars of which will be
found in the Philosophical Magazine of
(we believe) 1840-41. But our readers
need not trouble to refer to those works.
A walk from Rosherville to a mile be-
yond Gravesend, or near Hastings, Ryde,
Southampton, &c, at places where the
sewage runs over the low-water shore,
will give sufficient evidence as to the
danger that may arise from the mixture
of sea-water and sewage. The sulphates
of the one and the vegetable and animal
matter of the other undergo mutual de-
composition, produce sulphuretted hy-
drogen and air poison. During the next
two months many thousands of persons
will visit three or four watering-places
on the Thames thus situated. One of
the most favorite of these resorts has the
reputation of possessing about three
344
VAN NOSTRAND's ENGINEERING MAGAZINE.
acres of cesspools in close proximity to
the sea— we mention no names. A
word to the wise should be sufficient.
But to resume the thread of our observ-
ations. During the last three months
samples were taken of the deposit left
at low water by the sewage between
Westminster Bridge and about two miles
below Gravesend. Some singular facts
were thus presented. Below Gravesend
the mud presents, when wet, a brown
appearance, turning to a blue or greyish
tint when dry. On analysis, this mud
seems to be the product of a gradual
and natural lime process of treating sew-
age. In other words, the bicarbonate of
lime held in solution seems to have pre-
cipitated portions of the organic matter.
Where clay is the most prevalent ma-
terial of the banks, the precipitate is
analogous to the so-called native guano,
produced by the ABC process. Anoth-
er singular fact is that the precipitates
have corresponding appearances when
wet. The clay precipitate has a peculiar
reflective surface, while the lime precip-
itate has a dull heavy surface, having no
reflective power. It is very possible
that the Thames possesses, by the vary-
ing constituents of its banks and bed, a
self -purifying power, but far from equal
to the requirements which four million
people insist on its performing. But
where neither clay nor lime present
themselves, no such result can exist, and,
consequently, between, say Poplar and
Westminster Bridge, the sewage deposit
wherever it exists, remains only to de-
compose, and therefore to poison the
air.
The effect of the in-coming tide is re-
markable. Taking the date of July 22,
the sea-water had reached Crossness at
about 6 p.m. Its freshness remained un-
impaired up to that point, the sea tint
being remarkably evident. But, above
Crossness, the freshness was lost. The
olive-green tint of the morning's observa-
tions was apparent, together with the
smell of bilge water. Off Blackwall, the
Thames was of a brownish-yellow tint,
and at London Bridge at the moment of
high-water it was evident that the com-
paratively stagnant lake, that had been
oscillating to and fro, was still as bad as
it was ten or twelve hours previously,
and the same observation held good as
far as Hungerford.
Although we # have chosen a special
date, because no possible intervening
cause could have disadvantageously in-
fluenced the observations above related,
it must be distinctly understood that
precisely similar circumstances occurred
during three months, and we may add to
some extent for the last three or four
past years. We feel therefore compelled
to the belief that the conditions of the
Thames (within the limits assigned) are
as follows:
1. That the metropolitan sewage area
of the Thames may be considered as
bounded east at a little below Gravesend
(perhaps at Sea Reach) with a wall of
sea-water, and on the west, at a little
above Battersea, by a wall of fresh
water.
2. That while neither of the bound-
aries are exact, they furnish two differ-
ent results. The sewage may pass, and
no doubt does pass far beyond Battersea,
but is then diluted with fresh water
from the Upper Thames, despite sewage
contamination from riparian towns, &c,
such as Richmond, Kingston, Isleworth
and the like. On the other hand, the
eastern boundary supplies, by a flood
tide, sea-water which by under currents
runs perhaps beyond London Bridge.
3. That for all practical purposes, the
sewage cast into the Thames at Barking
and Crossness may be considered as lo-
cated between such boundaries oscilla-
ting with the tide; that, meanwhile, in
hot weather (80 deg. Fahr. atmospheric
temperature) it fosters the growth of
sewage fungus, confervoid matter, &c,
to which it acts as a manure.
4. That there is a natural process of
defecation going on, partly by rainfall,
the action of lime and clay, as already
pointed out, and the disturbing action
of steam and other vessels. But, on the
other hand, the faecal and other matter
cast from these vessels into the river
may, to a large extent, add to the pollu-
tion of this stream.
5. It would appear that whatever endeav-
ors are made at Barking and Crossness
to retain suspended matter by the settling
tanks, such exertions are practically fu-
tile, so far as the physiological condi-
tions of the river are concerned. It is
impossible, in the few hours during
which settling can take place, that more
than a small portion of the suspended
THE RIVER THAMES.
345
matter can be removed. Referring to
experiments made at Leeds it was found
that, after a few days, entire settlement
of suspended matter was not effected in
glass vessels that were never disturbed.
But, if we take into account the rush of
new sewage into a tank hourly, changes
of temperature and a variety of other
concomitant circumstances, too numerous
to mention, any " settlement " at either
Barking or Crossness is simply nomi-
nal.
The present state of the Thames has
been made the subject of investigation
during the last few weeks by Mr. Buck-
land, with special relation to the interest
of the fishermen, and at a lecture that
gentleman lately gave, the results of his
investigation showed that the loss in a
pecuniary point of view to London is
very heavy. Some conversations that
we have recently had with old fishermen
residing at and below Gravesend, lead to
the same conclusion. As early as the 12
Richard II a statute was passed enjoin-
ing the mayors of boroughs to make
proclamations against throwing filth or
rubbish into rivers. No communication
between the cesspools of the houses and
the sewers of the streets was permitted
until 1847, and now we find the Thames
converted into a kind of running cess-
pool, in that portion of the metropolis
which contains most of its wealth and
intelligence.
As we fully anticipated, the Rivers
Pollution Prevention Act is practically a
dead letter. So far as the metropolis is
concerned, the Metropolitan Board is, in
the name of the ratepayers, a licensed
polluter. Far be it from us to lend the
least sanction to some of the wild
schemes that have been held out by vari-
ous companies and individuals to cure
these evils. But here we have some un-
deniable facts. We have a river running
through London for a distance of, say,
twenty miles, which nominally carries
away, but really retains, the sewage of
4,000,000 persons. From its surface there
exhale noxious gases, and on its banks
equally noxious manufactures are carried
on. The Statute Book shows laws
against all these evils, but the most in-
terested parties to retain the evils are
those who have to put such laws into
force. If this is not putting into defiance
all common sense and sanitary improve-
ment, we should be at a loss to find an-
other instance. Meanwhile the kings
play while the common people perish.
The Board of Trade falls out with the
Metropolitan Board, the Thames Con-
servancy with the latter, the Courts of
Chancery are afraid to stir, and " grant
time," and thus, year after year, matters
progress nominally, while if we take the
veil off the sight, we find ourselves
gradually walking backwards, or, to use
more modern and political phraseology,
in a state of retrocession to conditions
that were abominated twenty years ago.
THE CONSERVANCY OF RIVERS AND STREAMS.
By EDWABD EASTON, Esq., President of the Section of Mechanical Science.
Paper read before Section G of the British Association— Dublin Meeting.
By the conservancy of rivers and
streams I mean the treatment and regu-
lation of all the water that falls on these
islands from its first arrival in the shape
of rain and dew to its final disappearance
in the ocean.
I had at first, in my ignorance, con-
templated treating the subject in a still
wider manner by referring to the rivers
and streams of other countries ; but I
soon found that, without going beyond
our own, the vast extent of the field to
be traversed would make it extremely
unlikely that I could, with any satisfac-
tory result, attempt even the more
restricted task which I have now before
me.
The question of conservancy of rivers
and streams involves the consideration
of their regulation for the following
principal purposes :
1. For the supply of pure and whole-
some water for the domestic and sanitary
wants of the population.
346
VAN NOSTRAND'S ENGINEERING MAGAZINE.
2. For the supply of water of proper
quality and sufficient quantity for indus-
trial purposes.
3. For the proper development of
water power.
4. For the drainage and irrigation of
land.
5. For navigation and commerce.
6. For the preservation of fish.
In the early days of the world's history
there were attempts made to regulate
and control the waters of rivers — some
of them devoted to military and dynastic
objects, but the majority to generally
useful ends. Herodotus, speaking of
Semiramis, who lived some 2000 years
b. c, tells us that she raised certain
embankments, well worthy of inspection,
in the plain near Babylon, to control the
River Euphrates, which till then used to
overflow and flood the whole country
round about. He also mentions a lady,
who lived at a still earlier period, who
altered the course of the same river, as a
defence against the Medes, to such an
extent that, " whereas the River Euphra-
tes ran formerly with a straight course
to Babylon, Nitocris, by certain excava-
tions which she made at some distance
up the stream, rendered it so winding
that it comes three several times within
sight of the same village " (Ardericca, in
Assyria). " She also made an embank-
ment along each side of the Euphrates,
wonderful both for breadth and height,
and dug a basin for a lake a great way
above Babylon, close alongside of the
stream, which basin was sunk every-
where to the point at which they came
to water, and was of such breadth that its
whole circuit measured 420 stadii (more
than 50 miles). The soil dug out of
this basin was used in the embankments
along the water side. When the excava-
tion was finished she had stones brought,
and bordered with them the entire
margin of the reservoir. These two
things were done — the river made to
wind, and the lake excavated — that the
stream might be slacker by reason of the
number of curves and the voyage render-
ed circuitous, and that at the end of the
journey it might be necessary to skirt
the lake, and so make a long round. All
these works were on the side of Babylon
where the passes lay, and the roads into
Media were the straightest; and the aim
of Nitocris in making them was to pre-
vent the Medes from holding intercourse
with the Babylonians, and so to keep
them in ignorance of her affairs." The
same energetic princess made brick em-
bankments and quays, and a bridge over
the Euphrates, and to do this she turned
the entire stream of the river into an
artificial cutting, the natural channel
being left temporarily dry until the
bridge was finished, when the Euphrates
was allowed to flow into its ancient bed.
It was into this very cutting that Cyrus
directed the course of the Euphrates
when he took Babylon, 538 b. c. In the
time of Herodotus himself, about b. c,
450, there were embankments to the
river at Babylon ; for he says, " the city
wall is brought down on both sides to
the edge of the stream; thence from the
corners of the wall there is carried along
each bank of the river a fence of burnt
bricks, with low brazen gates opening on
the water."
The same historian, in his second book,
describes the hydraulic works of the first
king of Egypt, Men or Menes, which
were not only gigantic in themselves, but
productive of the most important results
to the inhabitants of his kingdom. "Be-
fore his time," Herodotus says, "the
river flowed entirely along the sandy
range of hills which skirt Egypt on the
west side. He, however, by banking up
the river at the bend which forms about
100 furlongs south of Memphis, laid the
ancient channel dry, and dug a new
course for the stream half way between
the two lines of hills.
Passing to Greece, perhaps the most
wonderful instance of the successful reg-
ulation of water is to be found in the
subterranean channels (the modern Greek
Katabothra) by which the waters of the
River Cephius are carried through Lake
Topolias (the ancient Copias) into the
sea. These tunnels, which are partly
natural and partly artificial, have always
served to prevent the lake overflowing
the adjoining country.
The well-known tunnel, or emissarium,
from the Alban Lake is an example of
Roman work. This tunnel, of a man's
height, and cut through 6000 feet of
lava, is said to have been begun in obe-
dience to the Delphic oracle in the sixth
year of the siege of Yeii, b. c. 398. By
it, the over-flow of the lake which used
periodically to flood the Campagna was
THE CONSERVANCY OF RIVERS AND STREAMS.
347
prevented, and the waters were conduct-
ed through it in an even flow for the
irrigation of the fields which it had
formerly laid waste. Three vertical
shafts and one made in an oblique direc-
tion still remain ; the marks on the hard
rock show that the chisels employed in
the cutting were an inch in width.
Another Roman work of still greater
importance was the emissarium at Lake
Fucino, planned by Julius Caesar and
carried into execution by Claudius. This
was a tunnel three miles in length, ex-
tending from the lake to the River Liris
(the modern Garigliano), one mile of it
being driven through a mountain of cor-
nelian rising 3000 feet above the lake.
It employed 30,000 men for eleven years.
There are many perpendicular shafts for
raising the rock to the surface and later-
al galleries for disposing of the spoil, so
as to enable this large number of men to
work without interfering with each
other.
The supply of water to different cities
of the ancients has been the motive for
the execution of the most stupendous
works, which are almost numberless. It
will be sufficient for me to allude to the
works constructed for the supply of the
city of Samos, about the time of Poly-
crates, b. o. 530, in which case a tunnel
was driven through a hill 150 fathoms
high for a length of 7 furlongs. Its
height and width were each 8 feet, and
it conveyed the water from the River
Ampelus into the city. Herodotus tells
us that the architect was Eupalinus, the
son of Naustrophus, a Megarian. Sir
George Wilkinson, in a note on the text,
mentions the fact that a French traveler,
M. Guerin, discovered one mouth of this
tunnel to the north-west of the harbor of
Samos, and cleared it from sand and
stones to a distance of 540 paces.
It is sometimes asserted that the
ancients were ignorant of the hydrostatic
law that water finds its own level. This
is not the case. Frontinus, who preceded
Agricola, the father-in-law of Tacitus, as
Governor of Britain, and who was Cura-
tor Aquarum in Rome under Nerva and
Trajan, mentions in his book, "De Aquae-
ductibus Urbis Romae," that in case of
the fracture of an aqueduct, the water
could be dammed up at each side of the
point of fracture, and carried over the
intervening space in leaden pipes. A
great deal of the internal distribution of
the water in Rome was managed by lead-
en pipes under pressure.
The aqueduct which Herod is said to
have constructed for the supply of
Jerusalem crossed a deep valley — near
Rachel's Tomb — by means of a stone
pipe working under pressure. This
work has been fully described by Mr.
Telford Macneill in the report made by
Sir John Macneill to the committee for
supplying Jerusalem with water. The
construction of the pipe is so remarkable
that I shall give Mr. Macneill's descrip-
tion in detail. It consists of great blocks
of stone through which holes 15 inches
in diameter have been cut. One end of
each block has been hollowed out to a
depth of 4-| inches, with a diameter of
24 inches, thus leaving a recess 4£ inches
wide to form the socket of the pipe.
The other end has a projection of a size
to fit a similar socket in the pipe which
lies next to it. This answers to the
spigot a modern cast-iron water-pipe.
Both socket and spigot are ground, so as
to fit with great accuracy, and the joint
is made with cement, which has set as
hard as the stone itself. The whole line
of these stone pipes is surrounded with
rubble masonry. The pressure on the
center of this very remarkable inverted
siphon is not less than 70 lbs. per square
inch.
The Arabs at a later period not only
knew of this law, but also understood
the operation of what we engineers call
the "hydraulic mean gradient." The
aqueducts constructed by them for sup-
plying Constantinople with water have
been very fully described in the most
interesting " Letters from Turkey," writ-
ten by Field-Marshal von Moltke in the
years 1835 to 1839. He says that the
Arabs knew that water under pressure
reaches its own level (seich gleich stellt),
for they conveyed the water across the
valleys in leaden pipes. They had found
by experience that the friction through
the aqueduct was lessened if openings
were made in the course of the line of
pipes; and along hill-sides and in places
where the pipes are not in deep cuttings,
funnel-shaped shafts or wells are made,
which acted as air-holes. But in cross-
ing deep valleys, where, of course, no
such holes could be made, they built
stone pyramids, called " Suterasi, " or
348
YAN ETOSTRAND'S ENGINEEEING MAGAZINE.
water-balances, on the top of which they
placed small basins, into and out of
which the water was conducted by a
leaden pipe laid up on one side of the
pyramid and down the other. The level
of these basins was so arranged that they
were at an inclination rather greater
than the average fall of the aqueduct;
and thus they allowed the water to take
the hydraulic mean gradient due to the
head necessary for the delivery of the
water. It is probable that these
"suterasi" were made about 1000 a.d.
In Britain the Romans without doubt
constructed embankments for the control
of rivers, but for at least 1000 years
after their time very little was done in
the way of great public works of this
description ; and it was not until the
beginning of the sixteenth century that
the state of the rivers in Italy command-
ed the attention of the great land-owners
and scientific men of that country. At
that time, chiefly in consequence of the
appointment of a Commission in 1516 by
Francis I, works for remedying existing
evils were seriously thought of : and for
a long series of years the most eminent
mathematicians and engineers were en-
gaged in investigating the subject and
in designing and carrying out works of
greater or less magnitude. A very full
collection, both of the writings of these
Italian engineers and of the descriptions
of their works, is contained in a book of
thirteen volumes, published at Bologna, in
1821-24, entitled "Raccolta d'Autori Ital-
iani che trattano del Moto dell'Acque. "
It would seem that about the same time
the question began to excite interest in
England, for it was in the reign of
Henry VIII, that a public statute first
dealt with river conservancy. But it is
to be remarked that neither in Italy nor
in England was the question treated in
anything like an exhaustive manner.
The great hydraulic works of Italy relate
almost exclusively to irrigation and nav-
igation, whilst the drainage of lands and
the prevention of floods were the objects
of legislation in England. During the
same period the Dutch were of course
constructing many important hydraulic
works; but these, from the special cir-
cumstances of the country, were not such
as to have much bearing on the general
question of the conservancy of rivers.
After the drainage of the Fens, the
next great works in England were the
canals, which, in a very few years, ex-
tended over the whole of England, and
formed a complete system for the con-
veyance of traffic. It is superfluous to
say that their construction and mainten-
ance had a strong bearing upon the
regulation of rivers. The well-known
saying of Brindley that rivers were
"principally valuable for feeding canals"
sufficiently indicates the subserviency of
the other interests involved. Next the
introduction of railways and steamboats,
and the increase in the size of ships,
turned the attention of those interested
in rivers to the improvement of the tidal
harbors and channels ; and from that
time to the present the greatest hydraulic
works of our time have been connected
with navigation. The concurrent in-
crease in manufactures necessitated the
employment of water in ways apparently
antagonistic to other interests, and intro-
duced the new element of pollution of
our rivers and streams, whilst the de-
mands of sanitary legislation, consequent
on the great increase of population, made
it imperatively necessary that their
purity should be maintained. Indeed, we
may say that the present high state of
civilization in which we live has involved
greater complications in this as in
other departments of life, and requires
special arrangements to meet them.
Legal enactments for the regulation of
rivers, and for defining the rights of
property in water, have existed from
very early times. Solon laid down that
to intercept the supply or to corrupt the
quality of water is a crime. He also
enacted that if any one dug a well to a
depth of ten fathoms (opyvlat) without
finding water, he should be permitted to
take from his neighbor's well a pitcher
of six %6eg (about 18 quarts) twice a day.
Plato, in his Laws, mentions an analo-
gous provision, but confines it to drink-
ing water only. Another law quoted by
him is more to the point; it runs as
follows : " If after heavy rains any of
the lower riparian proprietors should
injure a neighbor who lives above them,
by stopping the downward flow of the
water, or in case, on the other hand, the
proprietor living higher up shall injure
his neighbor below, by negligently allow-
ing the water to run down upon him,
either of them may call in the magis-
THE CONSERVANCY OF EIVEES AND STEEAMS.
349
trates and obtain a decision for the
guidance of both parties. If either party-
fail to abide by such decision, he shall be
punished for the enviousness and peevish-
ness of his spirit, and shall pay double
damages to the injured person."
The Pandects of Justinian, which are
a collection of all the old legal authori-
ties of Roman law, analogous to our own
reported cases, contain a variety of
leading principles which govern the
administration of the law of running
water : principles identical mainly with
that of our own common law. Some of
these related to fishing, watering cattle,
to the interruption of navigation of lakes,
canals, and ponds, to the preservation of
the water supply, to the repairs of river
banks, and to the regulation of the sum-
mer and winter flow of what are termed
public rivers. It was enacted among
other things, that nothing should be
done to the stream or banks of a public
river, whereby the flow should be altered
from its state in the preceding summer.
The earliest record in our own statute
law of any enactment relating to rivers
is that contained in 25 Edward III, c. 4,
which legalized all " gorces, mills, wears,
stanks, stakes and kiddles, " of a date
previous to "the reign of his grandfather
Edward I, by which the common pas-
sage de neefs et batelx en les grantz
rivers d'Engleterre be oftentimes annoy-
ed," and ordered the immediate pulling
down of all such erections which were of
a later date.
From that time, until the enactment
of Henry VIII, there were various laws
passed, chiefly relating to the naviga-
tions and rights of mills, and occasionally
to the preservation of fish. After Henry
VIII, very many private acts and chart-
ers granting powers for the drainage and
reclamation of lands, for improvement of
navigation, and matters of a similar
kind, were passed from time to time. A
great number also of royal commissions
and select committees have conducted
inquiries, and made reports upon most
of the various branches of the subject,
e. g. the pollution of rivers, the water
supply, arterial drainage, navigation, fish-
eries, &c, but until the appointment last
year of the Select Committee presided
over by the Duke of Richmond, no
attempt, as far as I am aware, has been
made to grapple with the question as a
whole, and the report made by them to
the House of Lords omitted to deal
with, at least, two of the objects I have
indicated as being necessary to the
proper consideration of the subject.
The recommendations made in the
report of that Committee were most
important, and they will, if carried out,
remove many of the difficulties which
stand in the way of a complete system
of conservancy of our rivers.
So much has been written on the engi-
neering details of this subject, by men
far better qualified than I am to deal
with them, that I shall confine myself to
the simple statement of the principles
which have been recognized by the chief
authorities as essential, and to a few
suggestions, which my own experience
leads me to think may be of some value.
Almost all the great engineers of former
generations, who have paid attention to
this question, Smeaton, Telford, Rennie,
Golborne, Mylne, Walker, Rendel, Ste-
phenson, Jessop, Chapman, Beardmore,
and without mentioning names, many of
the most eminent now living, have agreed
to the following general propositions:
That the freer the admission of the
tidal water, the better adapted is the
river for all purposes, whether of navi-
gation, drainage, or fisheries.
That its sectional area and inclination
should be made to suit the required
carrying power of the river throughout
its entire length, both for the ordinary
flow of the water, and for floods.
That the downward flow of the upland
water should be equalized as much as
possible throughout the entire year; and
That all abnormal contaminations
should be removed from the streams.
In carrying out these principles, it is
perhaps superfluous to say, that modifi-
cations must be introduced to suit the
particular phenomena of each river. In
some watershed areas, it would be easy
to construct reservoirs, which would to
a great extent equalize the flow and
reduce floods. In others it might be
better to control the floods by means of
embankments. In others, to have weirs,
and sluices, delivering into side channels,
parallel to the main stream, with the
same object. Sometimes reservoirs or
receptacles, must be made for catching
the debris brought down by the streams.
In fact, every river must be treated as a
350
VAN NOSTKAND'S ENGINEEKING MAGAZINE.
separate entity. It is therefore necessary
that a systematic collection of data, rela-
ting to rainfall, the geological character
of the gathering ground, and the volume
of each separate stream, should be made
for each watershed area; and this should
be carried on for a sufficient length of
time to enable a fairly correct estimate
to be formed of the behavior of the river
both in time of flood and in time of
drought. The establishment of self-act-
ing tide-registering gauges at several
points of every outfall should be insisted
on. By these means the whole of the
phenomena of a watershed area could be
ascertained and recorded, and safe and
trustworthy knowledge could be obtain-
ed, which would contribute towards the
determination, not only of the works
which ought to be executed, but of the
incidence of the taxation by which the
necessary funds should be raised. For
instance, it is obvious that where the
geological character of a watershed is
variable, one portion of it consisting of a
permeable stratum, such as chalk or red
sandstone, and another portion of an
impervious stratum, such as the tertiary
clays or the shales of the millstone grit,
the same works would not be adapted to
each section of the river, nor would it be
fair to charge all the expense according
to the same scale of contribution. The
former, that is the permeable stratum, is
not only, from its absorbent nature, not
the cause of floods, but is, by reason of
that characteristic, absolutely constituted
by nature one of the very works which
must be devised by art to mitigate the
effects of rainfall on the latter, or imper-
vious stratum.
Bearing this in mind, I have often
thought that nature might be usefully
imitated in this operation, by passing
the surplus rainfall into the permeable
strata of the earth by means of wells, or
shafts, sunk through the impermeable
strata overlying them. This has been
done in isolated cases for the drainage of
lands, but not for the deliberate purpose
of preventing floods and equalizing the
flow of rivers.
I also wish to remark that artificial
compensating reservoirs may be much
more frequently made use of than is gen-
erally supposed to be possible, when it is
considered that, so long as the dams are
constructed in situations where there is
no danger of their giving away, it is by
no means necessary that they should be
water-tight, and that, therefore, they can
be constructed at a very much smaller
outlay. In fact, the purpose would be
answered by a series of open weirs,
which would collect the water in times
of flood and discharge it gradually down
the stream.
The example of our French neighbors
in the more general use they make of
movable weirs — barrages — of various
constructions could, I am satisfied, be
followed by us with very great advant-
age in many cases.
The question of water power is one
which, I think, deserves more considera-
tion than it has lately received. It has
been the fashion to consider that small
water mills are of little or no value, and,
in the present state of most rivers and
streams, this is to a very great extent
true, but only because the supply of
water to work them is so variable and
uncertain. Sufficient attention has never
yet been given to the subject of .the
amount of compensation water which
should be given for the use of riparian,
proprietors, when the watershed areas
are dealt with for purposes of water
supply. There is a kind of empirical
rule acknowledged by most of the emi-
nent water engineers, that one-third of
the average flow of three consecutive
dry years is a fair equivalent for the
abstraction of the water falling on a
gathering ground. I am strongly of the
opinion that, looking to imperial inter-
ests, advantage should be taken of every
opportunity of dealing with a gathering
ground to provide for a much larger pro-
portion of its available water being sent
down the streams, so that the natural
water power of the country may be prop-
erly developed. The extra cost of the
necessary works must, as a matter of
course, be borne rateably by the interests
benefited. It is certain that with the
progress of invention many more ways
of utilizing this power will be discovered.
At present, through the medium of com-
pressed air, of hydraulic pressure, and of
electro-motors, the great disadvantage
of its being only available at the spot
where the water runs is overcome, and
the power can be transmitted to any
distance, and used wherever it may be
most conveniently applied.
THE CONSEEVANCY OF EIVEES AND STEEAMS.
351
Sir Robert Kane, in his most valuable
and exhaustive work on the " Industrial
Resources of Ireland, " has given an
estimate of the value of the power allow-
ed to escape every year in the shape of
floods, and the same calculation might
be applied to the sister kingdom. It is
probably no exaggeration to say that
where running streams exist the power
required for estate purposes, on the
majority of properties in the United
Kingdom, might be obtained by a prop-
er conservation of the natural water
resources of those streams.
The consideration I have been able to
give this subject, has helped to convince
me that, although a vast amount of labor
and research has been devoted to it, it
is nevertheless one in which " a more
systematic direction to scientific inquiry"
is urgently needed.
A vast collection of scientific facts
exists, but they require arrangement and
collation, and future observations should
be more strictly classified, so that the
bearing of each one, both on the others
and on the subject at large, may be
properly appreciated with a view to a
practical result.
In France this is being done to a very
large extent, and an excellent map show-
ing the phenomena of the rivers and
streams of that country is now in course
of preparation. For many years also
very accurate observations of the pheno-
mena of the whole of the basin of the
Seine have been taken, and have been
centralised (centralisees) by that eminent
engineer, whose loss, all who had the
privilege of knowing him, either in his
work or in private intercourse, are deplor-
ing, M. Belgrand, late Inspector-General
of the Ponts et Chaussees, and by his
able coadjutor, M. M. G. Lemoine.
These observations have been published
in the form of diagrams, admirable in
their simplicity of design, which show at
a glance the bearing of every one of
those phenomena on the general charac-
ter of that river.
In Italy also, where there exists a
distinct department having control of
the hydraulic works of that country, the
same exhaustive system of collation and
record has been followed, and the results
have been published in a series of Tables.
In Germany, although the same complete
system is not in vogue, its chief river
has been the subject of most thorough
investigation, the results of which have
been published in a beautiful map of the
Rhine and its regulating works.
In our own country, as might be
expected from the number of engineer-
ing works which have been executed,
there probably exists an amount of
detailed information on special and often
minute points which is unsurpassed and,
probably, unequalled in the world.
But, although as I have said before, a
great number of eminent men have treat-
ed in an exhaustive manner the pheno-
mena relating to many of the principal
rivers of Great Britain and Ireland; yet,
as far as I am aware, there has been no
attempt to collect and combine these
most valuable, though detached frag-
ments of knowledge, so that their relation
to one another might be seen, and a gen-
eral conclusion arrived at. This can
only be done by the establishment of a
public department analogous to those
described as already existing in France
and Italy.
I do not wish to be understood that, in
suggesting the collection of additional
data relating to the phenomena of rivers,
I am advocating delay in dealing with
the existing state of things until the
facts have all been ascertained. On the
contrary, I believe that the first step
ought to be the establishment of a di's-
tinct water department, which should at
once address itself to the remedying of
the evils which are found to be most
pressing. The time has long since ar-
rived when the present 'neglected state
of many of our most important streams
should be dealt with, and that this was
also the conviction of Parliament and of
the Government is evident, from the
appointment of so influential a commit-
tee as that presided over by the Duke of
Richmond last session.
Even the imperfect sketch which I
have been able to place before you will
have made manifest, I think, the enor-
mous importance of the subject and of
the interests involved — interests subject
to periodical losses arising from the
present imperfect organization, or I may
say, the present entire want of organiza-
tion— losses which are not only monetary,
and therefore to a certain extent capable
of being estimated, but which affect
health and imperil life, and on that
352
vor nosteand's engineeeing magazine.
account, as is the unhappy experience of
the highest as well as the lowest of the
community, utterly incapable of appre-
ciation. How, for instance, can we
estimate the loss sustained by the coun-
try at large by the premature death of
that noble-minded and accomplished
gentleman, the Prince Consort, whose
life and energies were devoted to the
encouragement of all the objects which
this Association is established to foster
and promote, and who showed his strong
sense of its usefulness by presiding at
one of its most brilliant meetings.
When it is considered that many lives
are annually sacrificed, either directly by
the action of floods, or by the indirect
but no less fatal influence of imperfect
drainage — when it is remembered that a
heavy flood, such as that of last year, or
that of the summer of 1875, entailed a
monetary loss of several millions sterling
in the three kingdoms — that during
every year a quantity of water flows to
waste, representing an available motive
power worth certainly not less than some
hundreds of thousands of pounds — that
there is a constant annual expenditure of
enormous amount for removing debris
from navigable channels, the accumula-
tion of which could be mainly, if not
entirely prevented, that the supply of
:food to our rapidly growing population,
dependent, as it is at present, upon
sources outside the country, would be
enormously increased by an adequate
protection of the fisheries — that the same
supply would be further greatly increased
by the extra production of the land
when increased facilities for drainage are
afforded — that, above all, the problem of
our national water supply, to which
public attention has of late been drawn
by H.R.H. the Prince of Wales, requires
for its solution investigations of the
widest possible nature, I believe it will
be allowed, that the question, as a whole,
of the management of rivers is of suffi-
cient importance to make it worthy of
being dealt with by new laws to be
framed in its exclusive behalf.
A new department should be created
— one not only endowed with powers
analogous to those of the Local Govern-
ment Board, but charged with the duty
of collecting and digesting for use all the
facts and knowledge necessary for a due
comprehension and satisfactory dealing
with every river basin, or watershed area
in the United Kingdom — a department
which should be presided over, if not by
a Cabinet Minister, at all events by a
member of the Government who can be
appealed to in Parliament.
The department should have entire
charge of, and control over, all estuaries
and navigable channels, both because
these are used by foreign vessels, and
therefore the responsibilities attaching to
their preservation are international, and
because they must be protected from
hostile attack, and on these accounts are
essentially imperial property. For the
same reason the cost of amending and
maintaining them should be defrayed out
of the Imperial exchequer.
As regards the regulation of the re-
mainder of the water-shed area, the con-
clusions arrived at in the report of the
Duke of Richmond's Select Committee
seem to me entirely satisfactory. I can-
not do better than give a few extracts
from that report. The Committee say—
" That in order to secure uniformity and
completeness of action, each catchment
area should, as a general rule, be placed
under a single body of conservators, who
should be responsible for maintaining
the river from its source to its outfall in
an efficient state. With regard, however,
to tributary streams, the care of these
might be entrusted to district commit-
tees, acting under the general direction
of the conservators; but near the point of
junction with the principal stream they
should be under the direct management
of the conservators of the main channel,
who should be a representative body
constituted of residents and owners of
property within the whole area of the
watershed." The committee go on to
say that " means should be taken to in-
sure the appointment of a Conservancy
Board for each watershed area," but that
application should "first be made by per-
sons interested in the district, and that
then the departmental authorities should
send inspectors to make local inquiries
and to report upon the "necessities and
capacities of the district, and suggest the
area and proportions of taxation."
The scheme with such modifications as
may be deemed necessary is then to be
embodied in a provisional order to be
submitted to Parliament for confirma-
tion. It will be seen that this mode of
THE CONSERVANCY OF RIVERS AND STREAMS.
353
procedure is precisely analogous to that
of the Local Government Board in rela-
tion to public health — a procedure which,
as I am able to state from practical
knowledge, works admirably in most
cases. The committee further recom-
mend that the provisions in any local or
other acts which would interfere with
the proposed scheme, should be repealed.
They are also of opinion that " the Con-
servancy Boards should be enabled to
execute the powers conferred on local
authorities by the Rivers Pollution and
Prevention Act." It will also be neces-
sary that their powers should extend to
the carrying out of any acts passed or to
be passed for the protection of the fish-
eries.
With regard to what is probably the
most important point of all, the finding
of the money necessary to carry out
these recommendations, the committee
advocate the introduction of a new prin-
ciple of taxation, the soundness of which
cannot be questioned. Instead of the
principle first introduced by the statute
of Henry VIII, and observed ever since,
of levying taxes in proportion to the
direct benefit conferred, the committee
propose that the rates should be distrib-
uted over the whole area of a watershed,
including not only the lands, but the
towns, and houses, and all other property
situate within that area. This is in fact
no more than a general application of
the law of highways, which in the time
of the Romans, according to Justinian,
applied equally to waterways. It is
perfectly just that every acre, the drain-
age of which contributes to the flow of
the streams and rivers and of every
watershed area, should in some propor-
tion or other, contribute also to the cost
of maintaining the channels of those
streams and rivers in an efficient state.
The incidence of the taxation must of
course, as has been pointed out, be
determined by the circumstances of each
particular case, but there is no doubt
that the conclusion of the Duke of Rich-
mond's committee, that "the taxation
should be levied on the basis of rateable
value," is the only sound, and at the
same time practical way of dealing with
this difficulty.
The word " taxation " is not, I fear,
generally connected with any idea of
profit to the individual taxpayer. But
in this case, as I hope in the course of
this address I have made clear, it is
probable that the prevention of large
present losses, and the advantages gained
by an improved system, will give not
only a fair but an ample return on the
capital expended.
It is my firm belief that an intelligent
management of watershed areas would
be compatible with an absolute profit to
every interest affected ; that we have
here no question of give and take, but
that in this, as in every other case, the
laws of nature, under proper and scien-
tific regulation, can be made subservient
to the needs of the highest civilization.
BRICKS ANJ) BRICKMAKING.
From "The Builder.
The science of agriculture no doubt
afforded the earliest scope for the exer-
cise of human skill and industry. The
Biblical narrative speaks of Abel as a
"keeper of sheep," and of Cain as a
" tiller of the ground." An application
to the mechanical industries allied with
arts of construction must, however, have
been very early forced upon man, in
order to supply implements of husbandry
and to provide places of habitation. We
read in the fourth chapter of Genesis
that Tubal-cain was " an instructor of
Vol. XIX.— No. 4—23
every artificer in brass and iron," or, ac-
cording to Gesenius, " a sharpener of
every kind of brazen and iron instru-
ment"; a reference clearly pointing to
the manufacture of tools required for the
purposes of the husbandman and proba-
bly of others used in connection with
constructive art, then in its rudest in-
fancy.
There is little doubt that clay, in com-
bination with such materials as would
bind it together in a compact mass, was
employed in the structure of the primi-
354
van nostrand' s engineering magazine.
tive human dwelling. In course of time
this method of construction was super-
seded by the use of the same plastic sub-
stance, moulded, either with or without
other ingredients, into suitable forms,
which were afterwards dried or burned,
the result being the production of the
article now known as " brick/' The de-
scendants of Noah are described in Gene-
sis xi. 3 (2247 B.C.) as making bricks and
burning them thoroughly, afterwards
laying them with " slime," — or, as some
translators read, " bitumen," — in the
place of the mortar now employed for
the same purpose. With the bricks
thus made they built the tower of Babel
" on a plain in the land of Shinar."
Some of the best authorities agree in re-
garding the ruins still standing at Birs-
Nimrud, to the south-west of Hillah,
near the Euphrates, as being the remains
of this tower; and it is a remarkable
fact that, after the lapse of ages, the
bricks of which it is constructed are so
firmly embedded in the bitumen used as
mortar that it is no easy task to detach
or extract one. The circumference of
the tower measures 762 yards, and a
conical elevation on the western side
rises to the height of 198 feet. The
various stages of brickwork are of diff-
erent colors, — a result which must have
been attained by some special process,
the ordinary Mesopotamian brick being
of a pale yellow or whitish colour. The
late Mr. George Smith, the indefatigable
Assyrian explorer, deciphered among the
tablets in the British Museum a history
of the building of this tower, which will
be found in his " Chaldean Account of
Genesis."
The mounds of Assyria and Babylonia
abound with bricks, sun-dried and burnt,
Rawlinson, Layard, Mignan, Rennel, and
other travelers having found thern^ in in-
calculable quantity. Modern research
has also confirmed the statement of
Herodotus, that from the clay thrown
out of the trench surrounding the ancient
Babylon, bricks were made and burnt,
which were used in building the massive
walls of the city. The buried palace of
Nebuchadnezzar on the Euphrates is said
to have furnished bricks for the erection
of all the buildings in its neighborhood
for many years past; and we are told
that " there is scarcely a house in Hillah
which is not almost entirely built with
them." Muller, in his " Science of Lan-
guage," says that the ancient materials
from the colossal palaces erected by the
great ruler of Babylon were carried
away for building new cities, and that
Sir Henry Rawlinson discovered num-
bers of the bricks in the walls of the
modern Bagdad on the borders of the
Tigris. No doubt can exist as to their
identity, owing to the custom which pre-
vailed in Assyria and Babylonia of
marking each brick with the name and
title of the king in whose reign it was
made, and also, in many instances, with
the name of the place in the construction
of which the brick was to be used.
These inscriptions are in cuneiform
characters, and were impressed upon the
brick in a sunken rectangular panel,
closely resembling that in which the
name and trade-mark of modern manu-
facturers of moulded bricks now appears.
From the presence of these inscriptions
Sir Henry Rawlinson has been able to
ascribe the manufacture of some of the
bricks found by him to the period of the
older kings of Babylon, who reigned
about 2000 B.C. In form, the ancient
Assyrian bricks closely resemble thick
tiles, being generally from 12£ inches to
14 J inches square, and about 4 inches in
thickness. They were almost universally
shaped in a mould, some being rounded
at the corners for quoins or special work.
Generally speaking, they were of a pale
yellow or red color. At Kouyunjik,
Nimroud, and other places, however,
bricks have been found glazed with a
thick coating of different colors, some
having subjects traced in outline upon
them. The walls of the city of Nineveh
are said to have been built with glazed
bricks of this description, and those of
the Median Ecbatana were constructed
of colored bricks. Enameled bricks,
brightly colored, have also been found
in abundance in the mound of the
Mujellibeh in Mesopotamia, the principal
tints being a very brilliant blue, a deep
yellow, red, white, and black.
In Egypt, bricks were used at a very
early date, some of the most ancient
Pyramids, built at least 2,000 B.C., be-
ing constructed of brickwork. The mud
of the Nile has always been the sole ma-
terial employed in the manufacture of
Egyptian bricks, and the process at the
present day is almost identical with that
BRICKS AND BRICKMAKING.
355
adopted in the time of Thothmes III, the
prince who is believed to have occupied
the Egyptian throne at the period of the
exodus of the Hebrews, about 1430 B.C.
Brickmaking, there is reason to believe,
was a royal monopoly in Egypt, and the
bricks which have been found bearing
the stamp of Thothmes III, are more
numerous than those of any other mon-
arch. Nearly all Egyptian bricks, both
ancient and modern, are adobe, or sun-
dried. A few burnt bricks have been
found in river walls or hydraulic works,
but their use was evidently very limited.
Owing to the rich alluvial character of
the mud of which the bricks are made,
chopped straw or reeds, pieces of pottery,
and other materials, are almost invaria-
bly used for the purpose of binding the
clay together. The modern process is to
form a trough or bed, into which mud
and water are thrown, together with
large quantities of cut straw. The mix-
ture is tramped into a mortar, taken out
in lumps, and then shaped, either by
hand or in moulds, into the required
forms. A painting discovered upon the
walls of one of the tombs at Thebes, in
which the processes employed in manu-
facturing bricks are represented with
striking minuteness of detail, shows how
closely these resemble the method still
adopted in Egypt. Some of the workers
are depicted as engaged in digging the
mud, and mixing it in heaps with sand,
while others carry the material thus pre-
pared in baskets to the brickmaker, who
is seen shaping it in the mould. Others,
again, are employed either in laying out
the bricks thus formed upon the ground
to dry in the sun, or in bringing from
the river, in jars upon their shoulders,
the water required for tempering purpos-
es. Laborers, too, are busily engaged
in removing the dried bricks upon flat
boards, two of these being slung by
ropes attached to each end of a yoke
placed across the shoulders. Task-
masters are also shown, watching over
and directing the operations, stick in
hand, ready to inflict summary punish-
ment on the idle or the refractory.
Brickmaking, it must be remembered,
was regarded in Egypt as a degrading
task, and was usually assigned to slaves.
It formed the principal occupation of the
Israelites during their bondage in Egypt,
after the death of Joseph, and the griev-
ous addition to their toil necessitated by
the obligation to provide their own
straw may be readily estimated from
what has been already said as to the
process of manufacture. The bricks
made by them during their captivity
were probably used in the erection of the
great treasure- cities of Pithom and
Rameses. At a later date, we read of
the erection in Egypt of a brick pyramid
by Asychis, the monarch whose reign
immediately preceded that of Sethos, the
contemporary of Sennacherib and Tirha-
kah, about 700 B.C. This would proba-
bly be one of the four brick pyramids
still remaining in Lower Egypt in addi-
tion to those at Thebes. Two of these
are close to the ancient Memphis and the
modern Dashour, and the others are
situated at the mouth of the Fyoom.
They are built of sun-dried bricks, the
chambers having arched ceilings. Brick
arches are to be found, however, in build-
ings at Thebes of a much earlier date,
the arch having been invented and used
in Upper Egypt centuries before the
reign of Asychis. The ordinary Egypt-
ian brick approached somewhat to the
modern type, being generally from 14£
inches to 16 inches wide, and of a thick-
ness varying from 5 inches to 7 inches.
In the older pyramids they were of an
exceptional size, measuring in some cases
20 inches in length, and about 8 inches
in width. The bricks of Egypt, like
those of Assyria, bore the name of the
kings in whose reign they were manu-
factured, but, in place of being inscribed,
they were stamped, the hieroglyphs
being in relief.
In Palestine, in the time of the prophet
Isaiah, it is clear that bricks were used in
the construction of private dwellings
(Isaiah ix. 10), and one of the offenses
laid to the charge of the people of Israel
by the prophet was that of using brick
in place of stone, for the construction of
their altars (Isaiah lxv. 3).
Amongst the ancient Greeks, who
devoted special attention to every branch
of constructive art, the manufacture of
bricks was placed under legal supervision
and brought to a very high perfection.
Pliny mentions three distinct varieties as
being in general use, and alludes to the
circumstance that the walls of the city
of Athens, on the side towards Mount
Hymettus, were built of brick. Many
356
VAN NOSTRAND'S ENGINEERING MAGAZINE.
of the principal public edifices in the
leading cities of Greece were also of
brickwork, — perpendicular walls of this
construction being considered by the
Greek architects more durable than
those of stone.
Brickmaking was a nourishing indus-
try in the Roman Empire, both sun-dried
bricks (laterce crudi) and kiln-burnt
bricks (laterw cocti) being extensively
used in public buildings. All the great
existing ruins of ancient Rome are of
brick, and there is scarcely a province of
the once mighty empire which does not
still exhibit striking proofs of the dura-
bility of the bricks manufactured, and
the skill of the artificers who laid them,
in the days when Rome was mistress of
the world. In the erection of the
Coliseum, 80,000 captive Jews were em-
ployed, who probably helped to make
the bricks of which the noble structure
was built, as well as to lay them. The
use of bricks in the construction of the
public edifices of Rome was indeed so
general as to afford occasion for the
remark of the Emperor Augustus, with
reference to the numerous and extensive
architectural improvements he had car-
ried out, that "having found the city
brick, he had left it marble." To enum-
erate all the great public buildings which
thus bear witness to the excellence
attained by the Romans in the art of
brickmaking would be tedious. Among
the most notable, as illustrating the
progress made at different stages of the
history of the empire, are the Pillar of
Trajan, the Bath of Titus (A.D. 70), and
the Bath of Caracalla (A.D. 212). Not-
withstanding this very general employ-
ment of bricks in the construction of
public edifices, it may be inferred, from
the observations of Pliny, that they were
not commonly used in private houses, in
the building of which wood was proba-
bly the chief material ; a view which
would seem to be, to some extent,
confirmed by the extent and destructive-
ness of fires which occurred in ancient
Rome. Pliny, after referring to the
common use of bricks by the Greeks,
condemns them as wholly unsuited for
Roman dwellings, in which party walls
were not allowed to exceed 18 inches in
thickness, and that thickness he declares,
" would not support more than a single
story." At this period, the Roman
bricks varied considerably in size, but
were chiefly of three clases. The largest,
known as the Lydian, were 1 foot 6
inches in length by 1 foot in breadth,
and the others, which were respectively
four and five palms in length, took their
titles from their admeasurement. They
were all very much thinner than the
modern brick, more especially those em-
ployed as a bond in Roman rubble-con-
structions, which, in this respect, bore a
close resemblance to the wall-tiles of the
present day. The kiln-burnt bricks in
the Greek building at Treves called the
Palace of Constantine, are all " of a
square form, 3 inches in diameter, and
1^ inches thick." The custom of mark-
ing each brick, which has been alluded
to as prevailing amongst the Assyrians
and Egyptians, was maintained by the
Romans, the various brickmakers having
! each their distinguishing mark. Every
j brick was stamped with the figure of
J some god, plant, or other symbol, encir-
cled with the name of the maker, the
consulate, and the legion by which it
was used. The Twenty-second Legion
has been traced through Germany by
bricks which bear its name, and at Caer-
leon, in England, Roman bricks have
been discovered with the inscription
" Leg. II, Aug.," while others found at
York attest the presence there of the
Sixth and Ninth Legions. Some of these
bricks were scratched on the surface,
while others had lumps raised on them,
or were deeply notched, with the view
of making the mortar adhere more firm-
ly. The Romans preferred, for brick-
making purposes, a clay which was either
of a whitish hue or decidedly red. They
considered Spring the best time for
carrying on the process of manufacture,
and it was the general custom to keep
bricks two years in stock before laying
them.
With the decadence of the Roman
Empire, the art of brickmaking declined
and fell into disuse, but, after a few
centuries, experienced-a complete revival,
the Italian ecclesiastical and palatial
architecture of the Middle Ages being
distinguished by remarkably fine exam-
ples of brickwork and ornamental work
in terra-cotta. Towards the close of the
seventeenth century, an Italian, named
M. Fabbroni, rediscovered an ancient
invention, which had been completely
BRICKS AND BEICKMAKING.
357
lost for many generations, namely, the
manufacture of bricks sufficiently light
to float in water. Strabo speaks of
these bricks as having been made with
an earth found at Pisaue, in the Troad,
and Poseidonius mentions others of a
like character as having been made in
Spain "of an argillaceous earth, where-
with vessels of silver are cleansed "
(probably rottenstone). M. Fabbroni
succeeded in producing these floating
bricks from "fossil meal," an infusible
earth found in abundance over a consid-
erable area of certain districts in Italy.
They were only one-sixth the weight of
an ordinary clay brick, and on this
account were highly esteemed for vault-
ing church roofs and similar architectural
work. The eirth of which they were
composed consisted, according to Ehren-
berg, the German microscopist, almost
entirely of the siliceous skeletons of
minute water-plants. The bricks with
which the arching of the floor in the
Berlin Museum is built were made from
this material, in combination with a
certain proportion of clay "slip."
Among many of the Asiatic nations,
bricks of excellent quality have been
made from a very remote period, and
are to be found in buildings erected
centuries ago. A very full account of
the history of brick-making in India will
be found in the "Professional Papers on
Indian Engineering" of Major Falconnet,
R. E., published in May, 1874.
In China, bricks are faced with por-
celain, and in Nepaul they are richly
ornamented by the encaustic process and
in relief.
Brick-making was found by the con-
querors of Peru to be a flourishing indus-
try in the ancient empire of the Incas,
and we have the testimony of Spanish
historians, as well as that of Humboldt,
Prescott, Stephens and Squier, that both
in Peru and in the more northerly
regions of Yucatan, and Mexico, there
are still extant fine structures in brick,
as well as in porphyry and granite, the
work of races which have long since
passed away.
The scarcity of stone in Holland and
the Netherlands naturally led the in-
habitants, at a very early period, to
seek some other durable material for
building purposes, and brick has been
almost exclusively employed in the con-
j struction not only of private dwellings
i and commercial establishments, but of
ecclesiastical structures and other public
edifices. Very fine examples of brick-
work in two colors abound, the most
notable, perhaps, being at Leeuwardein,
in Friesland. The material used in
Dutch bricks is chiefly the slime deposit-
ed in the numerous rivers and arms of
the sea. This is collected by men in
boats, who use long poles, furnished at
the end with a cutting circle of iron, and
a bag-net with which the slime is
brought to the surface. Bricks of
exceptional hardness are made with a
mixture of this slime and sand from the
banks of the river Maas. Ordinary
house bricks and tiles are chiefly made
at Utrecht, from brick- earth found in
the vicinity. For the production of the
special make of bricks known as " Flem-
ish bricks," which are manufactured in
France, Flanders, and the corresponding
Belgian frontier, sand from the Scheldt
is principally used. At Ghent, as well
as at other points lower down the river,
the supply of this material constitutes
; an important branch of the trade of the
district. In preparing brick-earth, the
slime and sand are well mixed, and then
kneaded together with the feet, special
care being taken with this operation, so
that a perfectly homogeneous mass may
be the result. The mixture is then de-
posited in heaps, and is moulded and
dried in the same way as in this country.
' The kilns used for burning vary in size,
; some being large enough to contain as
many as 1,200,000 bricks. Peat is the
fuel ordinarily used for firing.
England seems to owe the introduction
of the art of brickmaking to the Romans.
Some specimens of their work which
have been discovered date back as far as
A.D. 44. The bricks in these early ex-
amples are nearly all of the wall-tile
form, the use of which, as a bond in rub-
ble construction, has been already ad-
verted to. These large thin bricks con-
, tinned in use, under the same conditions,
until about the time of the Norman Con-
quest, when regular masonry gradually
superseded rubble-work. A casual ref-
erence in the Saxon chronicles shows that
bricks were made under the direction of
i Alfred the Great, but these were proba-
! bly the bunding bricks just mentioned.
The earliest instance of the use of bricks
358
VAN NOSTRANCTS ENGINEERING MAGAZINE.
of the modern or Flemish type is said to
be afforded in the work at Little Wen-
ham Hall, Norfolk (A.D. 1260). These
bricks are of a deeper red than those
generally used in Suffolk and the adjacent
counties, but paler in tint than the com-
mon red brick. The use of brick in Eng-
land as an ordinary building material,
even for important structures, does not
seem to have become at all general until
the reign of Henry VIII, although there
are some few brick buildings of the two
previous reigns. Herstmonceaux Castle,
Sussex, and the Gate of the Rye House,
in Hertfordshire, were built in the early
part of the reign of Henry VI, and the
following are among the best examples
of erections in brick from this date to |
the close of the reign of Henry VIII : —
Tattershall Castle, Lincolnshire, A. D.
1440; Lollards' Tower, Lambeth Palace,
A.D. 1454; Oxborough Hall, Norfolk,
A.D. 1482 (about); Gateway of Hadleigh
Rectory, Suffolk, close of fifteenth cen-
tury; the older portions of Hampton
Court Palace, A.D. 1514; and Hengrave
Hall, Suffolk, A.D. 1538 (completed).
Thorpland Hall and the Manor House at
East Barsham, both in Norfolk, were
built during the reign of Henry VII, and
the Parsonage at Great Snoring, in the
same county, during that of his succes-
sor. The remains of these buildings ex-,
hibit some of the finest specimens of or-
namental brickwork to be found in this
country. Throughout the reign of Eliza-
beth, the employment of brick would
seem to have been reserved for the con-
struction of mansions and other extensive
works. In common buildings, the meth-
od ordinarily adopted was that of filling
in a framework of timber with lath and
plaster; and, even when the use of bricks
became general, they were only intro-
duced in panels between a framework of
timber. In the first year of the reign of
Charles I (1625) the size of bricks was
regulated by a special order, and from
about this period their use seems gradu-
ally to have become more general in
shops and private houses, for, on the re-
building of that portion of London which
was destroyed by the Great Fire in 1666,
the new erections were all of brickwork.
So rapidly did the use of the material
spread that the 19th Car. II, cap. 11,
fixes " the number of the bricks in the
thickness of the walls" of the several rates
of dwelling-houses of the period. The
records of the Corporation of the City
of London also furnish evidence of the
favor with which brick had come to be
regarded as a constructive material, for
about this time a resolution was passed
in the following terms : " That they (the
City surveyors) do encourage and give
directions to all builders, for ornament
sake, that the ornaments and projections
of the front buildings, be of rubbed
bricks; and that all the naked parts of
the walls may be done of rough bricks,
neatly wrought, or all rubbed, at the dis-
cretion of the builder." A special feature
of brickwork at the close of the seven-
teenth and commencement of the eight-
eenth century was the enrichment of
house-fronts by the introduction of orna-
ments carved with a chisel. Mr. Dob-
son's treatise on " Brick and Tile Mak-
ing," published in Weale's Rudimentary
Series, contains a sketch of a house in
St. Martin's Lane, built by a person
named May, about 1739, which is a fine
example of this species of work in red
brick. Two fluted Doric pilasters sup-
port an entablature, the mouldings, flut-
ings, and ornaments of the metopes, hav-
ing been carved with a chisel after the
erection of the walls.
In the year 1784 a duty of half-a-
crown per thousand was imposed on
bricks of all kinds (24 Geo. Ill, cap 24),
the tax being raised ten years after to 4s.
per thousand (34 Geo. Ill, cap. 15). In
1803 a classified schedule of duties on
bricks and tiles of different qualities and
sizes was substituted for the uniform
duty hitherto imposed. Thirty years
after (by the 3d Wm. IV, cap. 11), the
duty on bricks was again raised, the
common sorts being subjected to an im-
post of 5s. lOd. per thousand, while tiles
were wholly relieved from taxation.
These duties were the subject of a Com-
mission of Inquiry in 1836, and in 1839
the 2d and 3d Vic, cap. 24, relieved the
trade of the vexatious restrictions im-
posed by the schedule of duties hitherto
in force, and re-established a uniform
duty of 5s. lOd. per thousand on all
bricks " of which the cubical contents do
not exceed 150 cubic inches," without
regard to their form or quality. In 1850,
bricks ceased to be the subject of taxa-
tion, the duty being wholly repealed (13
Vic, cap. 9). The development of the
BRICKS AND BRICKMAKING.
359
brickmaking industry during the first
half of the nineteenth century may be
estimated from the following statement,
in round numbers, of the total make of
bricks upon which duty was paid at the
close of each decade from 1820 until the
repeal of the tax : — 1820, 914 millions;
1830, 1,100 millions; 1840, 1,400 millions;
1850, 1,700 millions. Four years later,
it was estimated that the total number
was considerably in excess of 2,000 mil-
lions, the capital employed in this branch
of industrial enterprise at that period
exceeding £2,000,000.
The employment of machinery in the
manufacture of bricks appears to have
had its origin either in this country or
in the United States. Some of the
earliest American patents were taken out
in 1792, 1793, 1800, 1802, 1806, and 1807.
The records containing the specifications
of these inventions were unfortunately
burnt in 1836. Prior to June of that
year, 122 patents for brick and tile ma-
chines had been granted in the United
States, and upwards of 500 have since
been taken out. In England, as early as
the year 1619, we find, among the Speci-
fications of Letters Patent, that the
eleventh granted was for the protection
of the "Arte of making a certain engine
to make and cast clay, &c." This first
idea of a machine for making bricks con-
sisted of a large pan or table, containing
moulds, which were filled with brick
earth and a heavy roller passed over
them to force the earth into the moulds.
The surplus clay was then scraped off the
top, and the bricks were ready for ejec-
tion from the moulds. This was, no
doubt, a somewhat crude arrangement,
but it approaches closely, in principle,
the most approved machines of the pres-
ent day. We do not, however, meet
with any record of the introduction of
brick-making machines, the operations of
which were regarded as a practical suc-
cess prior to the year 1839, when Messrs.
Cooke & Cuningham patented one,
which was capable of turning out 18,000
bricks in ten hours. In November,
1859, Mr. J. E. Clift, of Birmingham, at
a meeting of the Institution of Mechani-
cal Engineers, read a paper describing
Oates's brick-making machines, which
were then in use at Oldbury. The crush-
ing strength of the bricks made by these
machines was said to be 8,024 lbs. per
square inch as compared with 4,203 lbs.
in bricks made by hand from the same
material. The cost of Oates's machine
was from £150 to £200, exclusive of the
engine for driving it, and its turn-out
averaged 12,000 bricks per day, or about
twenty per minute. In 1861, Messrs.
Dixon and Corbett had a machine in
work in the neighborhood of Newcastle-
on-Tyne which was driven by steam
power, and turned out 1,500 bricks per
hour. The years 1861 and 1862 were
marked by special activity in the pro-
duction of these machines, the patents
granted during this period embracing
the following : — WimbalPs, Morrell &
Charnley's, Green & Wright's, Basford's,
Effertz's, Grimshaw's, Morris & Radford's,
Poole's, Newton's, Sharp & Balmer's,
Piatt & Richardson's, Foster's, and
Smith's. Up to the year 1868, forty-
seven patents relating to bricks and their
manufacture had been granted. During
the last twenty years many new machines
have been invented, and important im-
provements introduced, and probably
over 200 patents for machines connected
with the manufacture of bricks and tiles
are at present on record.
Mosandria — Another New Metal.
— According to the Correspondance Sci-
entifique of July 30th, Dr. J. Lawrence
Smith, Professor of Chemistry in the
University of Louisville, Kentucky, has
discovered a new metal belonging to the
cerium group, and has named it mosan-
drium, after Mosander, whose researches
on this class of metals are well known.
The new earth, mosandria, from which
the metal was obtained, differs from the
rest of the group of which yttria is the
head by its reaction with potassic sul-
phate, although what this reaction is
we are not informed. From cerium ox-
ide, mosandria differs by its solubility
in very weak nitric acid and in alkaline
solutions supersaturated with chlorine;
from lanthanium by the color of its oxide
and salts; and from didymium by cer-
tain dark rays in the bright part of the
spectrum. We shall refer at greater
length to this discovery in our next num-
ber, giving, if possible, the physical and
chemical properties of the new element.
— Chemical News.
360
VAN NOSTEAND7 S ENGINEEEING MAGAZINE.
A METHOD OF DEDUCING FORMULAE FROM EXPERIMENTS
ON WROUGHT IRON PILLARS.
By JOHN D. CKEHOKE.
Contributed to Van Nostrand's Magazine.
Since the ordinary equation for the
deflection of a beam is the equation of a
parabola, with reference to the length £,
and the deflection D, as the coordinates,
let us assume that the equation to the
curve of a given pillar sustaining a given
load, is the equation of a parabola. Al-
though this assumption may not entirely
accord with fact, practically it cannot be
very far from the truth, as will appear in
the sequel.
Let Fig. 1 represent a pillar sustaining
the weight or vertical pressure, P, with
the deflection, D, length, £, and least di-
ameter, h.
Then the equation to the curve of the
neutral line BCO, is
y1 = 2px.
if the origin is at C, and the axis of x
horizontal, and that of y, vertical. But
if O be taken as the origin and the axis
of y horizontal, and that of x vertical,
then the equation to the curve becomes,
after eliminating p,
J)
x*—lx-
4D
V-
(1)
Differentiating,
2xdx— Idx-
4D
dy.
4(2a;-Z)D
r
dx
d\j_ __8D
~dx>~ Z2
But we have the radius of curvature
(2)
1+W
(3)
dx2
_[Z4 + 16D2(2a-r)]f
8Dr
And, if x=%l,
r
^ = 8D'
for the value of the radius of curvature
at the center of the pillar.
This also follows from (2) and (3),
since at the center,
dy _
dx
Suppose that C, Fig. 2, is the center
of the neutral surface of the pillar, and
that CC, is equal to a unit of the length
of that surface, and that />, the radius of
curvature at the center, is represented by
CE. Let ab equal the decrement of a
unit of length on the compressed side of
the pillar, and afi^ the increment due to
FOEMULAE FROM EXPERIMENTS ON WROUGHT IRON PILLARS. 361
the same unit on the extended side of the
pillar. Take z equal to the distance of
the neutral surface from the surface of
the compressed side, and h equal to the
least diameter of the pillar at the center.
Then, according to the received theory,
we have
1 ab ab,
Whence
_1
z h p'
But ab + a1bl is the total difference of
length in the tw,o sides of the pillar for
a unit of its length. Therefore
ab + afix _ h _ 2B] _8DA
i ~~^~~w~~ir
and
BZ2
P z
h—z
ab + a1b1
h
ab
~ z
ab ab +
afi\
D =
±Eh
(4)
where Bx is the unknown bending unit-
strain on the fibres at the surfaces ab,
a1b1 of the pillar, and E is the modulus
of transverse elasticity.
Another expression for the central
deflection may be derived from the
equality between the total moments of
the external and the internal forces in
action.
The well known expression for the
moment of the internal forces, is
dition that -j- — o^ when x=^l, and again
with the condition that y=o when x = o,
we find after putting D for y and \l for
EID=API)^-PV2- (8)
If now we suppose the end moment M.
to vanish, we have at once
P = 9.6
EI
and
S
Q = 9.6
(A)
M^-EI^-
ax
(5)
where I denotes the moment of inertia
(so-called) of the cross-section of the
pillar, which is here supposed to be uni-
form throughout.
And the total moment due to the ex-
ternal force P acting vertically, and a
force at each end producing a couple
with the moment M„ tending to diminish
the deflection of the pillar, is
da?
Hence from (l)
rtfv 4PD
EI^=Py-li1.
Integrating
r
(V),
(6)
(v)
(a2 -fcO + M,.
first with the con-
where S=the area, and r=the radius of
gyration, of the cross-section of the pil-
lar; and Q is the vertical pressure upon
each unit of the cross-section of a pillar
having rounded ends that can produce
no end couples.
And here it may be noted that Weis-
bach, and Rankine, and Price, by a dif-
ferent method, find
EI EI
P = tt2— =9.8696044— ,
the first remarking that the formula
gives " generally a greater tenacity than
the formula for the crushing strength ";
the second, that this is the "smallest
value of P which is compatible with any
bending of the spring"; and the third,
that " hereby also we are enabled to cal-
culate the greatest weight that a vertical
pillar of a given form and height can
bear without being bent by the weight.''
Examples of the application of for-
mula (A), are given below.
Resuming equation (8), we have, if the
equal end-moments do not vanish,
M>=fPD p— (9)
Also from (6), the moment at the center
is
MC=PD— M, for external forces.
2BtI
1PD +
for internal forces.
8EID_2B1I
and, after dividing by S,
D:
12BrT
(Qf + 48Er2)A
which is the second expression
for the deflection.
(10)
sought
362
VAN nostrand's engineering magazine.
Equating (4) and (10) there results,
Qr=0, which is absurd.
^The source of this absurdity may be
found in equation (4); 'for since that
value of D was derived from curvature
alone, it is the value which D would
have from the unit-strain Bx, if Bx were
produced only by couples applied at the
ends of the pillar, without direct longi-
tudinal pressure. It is plain, therefore,
that the unit-strain Bx corresponds to a
smaller deflection when it is produced
by direct end-pressure, than when it is
produced by end-couples. The value,
R 72
■ * , given by (4), is, therefore, too
great, since we assume the unknown
value of Bx to be the same as the value
of B1 in (10).
Let us, therefore, correct equation (4)
and write
D=_M_ (11)
(4 + £)E/i v ;
so that from (10) and (11) we find
e—BL
12Er*
(12)
Now if, by resorting to experiments,
we can find some function of e which
shall be constant within given limits of
{l-7-r) or (l-^rh), we shall have within
those limits, a formula for the value of
Q in terms of I, r, E, and £.
The values of e in the following tables
have been computed from the experi-
ments upon wrought iron pillars, given
in Stoney's " Theory of Strains," and in
Lovett's " Report on the Progress of
Work, etc., of the Cincinnati Southern
Railway."
The tests, tabulated. in Mr. Stoney's
"Work, were made under the supervision
of Mr. Hodgkinson, and those recorded
by Mr. Lovett were made at Pittsburgh
and Chicago under competent engineers.
Neither of these sets of experiments
is so nearly complete as would be desira-
L— Solid Rectangular Pillars — Flat Ends.
See Stoney's Theory of Strains, page 263. Modulus of Elasticity, E =24, 000, 000 . r* =
r=radius of gyration, ^=least diameter, Z=length of pillar, 6=breadth.
Q=^-=resistance, in lbs. per square inch.
Gordon's Formula, as applied by Stoney to this case, is,
35840
Q= w—
i-r3000 h*
•
I
h
12Er2
Q by ex-
periment.
Excess over Q,
by
No.
b
I
Formulae
Formulae
Gordon
ins.
ins.
B, C, D, E.
B, C, F.
Formula.
1
2.980
120
238.569
1.9351
816
0
0
+ 978
2
2.983
90
179176
3.2238
2,410
0
0
+ 653
3
3.010
120
156.658
3.4553
3,379
- 172
— 190
+ 525
4
2.995
120
120.603
2.5939
4,280
+1131
+1151
+1848
5
2.980
60
118.343
3.2702
5,604
+ 15
+ 13
+ 719
6
2.980
60
118.343
3.2988
5,653
- 34
- 157
+ 670
7
3.005
90
90.452
3.1636
9,280
+ 339
+ 375
+ 336
8
5.860
90
90.407
3.3756
9,912
- 283
— 257
— 289
9
1.024
90
87.891
3.1392
9,753
+ 435
+ 346
+ 273
10
3.000
120
79.470
2.6743
10,165
+2296
+2054
+1377
11
3.010
60
78.227
3.3068
12,969
- 108
— 115
—1179
12
3.010
60
60.301
2.7374
18,067
- 701
— 648
—1865
13
5.480
60
60.241
2.6760
17,698
- 319
— 279
—1479
14
2.986
30
59.689
2.5019
16,853
+ 651
+ 566
— 470
15
3.000
90
58.824
2.8816
19,987
-2285
—2421
—3343
16
1.024
60
58.594
2.4702
17,268
+ 491
+ 358
— 555
17
3.010
30
39.319
1.6793
27,767
-3545
—6161
—4115
18
3.000
30
30.121
1.1210
29,655
+ 145
—5021
—2137
19
1.023
30
29.326
.9075
25,327
0
— 400
+2527
20
1.023
15
14.663
.3095
34,554
+ 559
— 758
—1105
21
1.023
7.5
7.331
.1090
48,682
0
+1257
—13473
FORMULAE FROM EXPERIMENTS ON WROUGHT IRON PILLARS. 363
ble, but they are offered as the best at
hand. Mr. Lovett says, " In order to
test thoroughly the mathematical cor-
rectness of the formula [Gordon's] ex-
periments should have been made with
the same pressure on columns of different
lengths and shapes of cross-section, made
of the same iron, of uniform quality,
and all fittings made, and measurements
taken with great precision. All these
conditions could not be realized."
In all the Hodgkinson tests here con-
sidered, E, the modulus of transverse
elasticity is taken at 24,000,000; which
is about the mean value of E found for
such iron by that experimenter. For the
Chicago and Pittsburgh tests, the values
of E are given, and the mean value
27,311,111 has been used except in the
case of " rounded or hinged ends."
From the tabulated values of £ we
may derive formulae as follows :
1. Take the arithmetical mean of all the
values of £ corresponding to (l—h)^>60
and (l-i-h) <180, except the anomalous
values in Kos. 4 and 10. This mean is
3.27916=*.
We have, therefore, £ itself approxi-
mately constant between these limits of
Q=3.279l6E^y=78699836^Y (B)
when (H-A) j^W
2. For values of (l-r-h) not greater
than 60, we observe that the product
h
yXfXQ,
is a function of e approximately con-
stant.
Using Nos. 12, 13, 14, and 16, and
taking means, we have
£=2.5964,
Q=17,427.
■•• wxTx59-65xli-3-596^
= 238.569, we may proceed as follows;
but the formula may not be reliable for
other cases, there being no intervening
series to give a law.
No. 1. No. 2. Dif. of logs.
log. (l-^-h), 2.3776132 2.2532793 0.1243339
" £ 0.2867054 0.5083644 0.2216590
Ratio of dif. of logs
I
.2216590
1.78277.
J 243339
/ l \1.78277
( — ) =33531, a constant
for thes^ two experiments.
/ h \3.7S277
.-. Q=33531E(Tj . (D)
4. Similarly may we find a formula for
values of (H-A)<30.
No. 19. No. 21. Dif. of logs,
log. (l^Jt), 1.4672457 0.8651857 0.6020600
" £ 9.9578640 9.0375286 0.9203354
Ratio of dif. of logs. =:^|^=1.52S64.
n .b020600
(7) \ 1.52864
—J .--.00518762, a constant
for these limits.
Wherefore,
Ql> I h V-52864
EA:
X
(4)
,00518762,
Q=124503
(4)
47136
(C)
5. Also for values of (l-rh) ranging
from 30 to 60, we may take
l^h 59.65 30 Dif. of logs.
log. (l—h), 1.7756104 1.4771213 0.2984891
" £ 0.4143716 0.0496056 0.3647660
Ratio of dif. of logs.=^|^=1.22204.
.017559, a constant.
1.22204
£X
Q=421419(A)
,77796
(B)
Q=134927
(F)
when {l-s-h) is not greater than 60.
3. For the extreme value of (l+h)
{l-rh), from 30 to 60.
(See Table II on following page.)
In the preceding table, under — , are
0
given the ratios of thickness of metal to
least diameter, or of thickness to the
mean of the two diameters when h and
b are different.
364
VAN NOSTRAND'S ENGINEERING MAGAZINE.
II. — Rectangular Tubular Pillars — Flat Ends.
See Stoney's Theory of Strains, page 271.
Notation as in preceding case. t= thickness of metal.
Gordon's Formula for this case,
P _ 30720
S
0,
1+
i2
3000 h<
Excess over Q, by
b
h
h
t
I
h
I
r
„_ Q*2
Qby
experi-
ment.
No.
Formulae
12Er2
Gordon
ins.
ins.
G, H.
Formula.
1
4.1
4.1
136.6
29.26
71.672
.19596
10,980
+4138
+2310
2
4.1
4.1
68
29.26
71.672
.34373
19,260
— 781
—1503
3
4.25
4.25
51
28.23
69.149
.41807
25,171
0
— 32
4
4.25
4.25
31.7
28.23
69.149
.35837
21,585
+ 288
— 619
5
8.1
4.1
70
29.26
66.452
.35525
23,169
+1756
+2809
6
8.17
4.1
100.6
29.26
66.394
.23268
15,201
— 733
— 248
7
8.4
4.25
32.3
28.23
64.104
.42778
29,981
+1798
+2881
8
8.5
4.75
25.1
25.30
57.906
.31334
26,913
+ 330
+1940
9
8.5
4.75
19
25 30
56.601
.27810
25,000
-2286
—1.297
10
4.25
4.25
31.7
21.10
51.684
.21421
23,201
+2522
+5226
11
8.17
4.1
100.6
22.40
50.902
.14588
16,215
— 636
+2079
12
8.1
4.1
69
22.30
50.669
.21538
24,111
+ 323
+3038
13
8.1
8.1
63.6
14.94
36.595
.09176
19,732
+3505
+4994
14
8.1
8.1
135
14.80
36.252
.06058
13,276
— 643
+1709
15
4.1
4.1
136.6
14.60
35.762
.05137
11,513
—1060
+ 35
16
8.1
8.1
63.6
14.57
35.689
.10216
23,100
—2721
—2612
17
8.37
8.37
60
14.33
35.101
.08712
20,364
+2637
+4993
18
8.37
8.37
38.2
14.33
35.101
.11001
25,716
—4529
—3104
19
8.40
8.40
35.7
14.33
35.101
.11413
26,675
—3100
—1826
20
4.25
4.25
50
14.10
34.538
.09793
23,584
+1287
+3550
21
8.1
8.1
135
11.30
27.679
.03539
13,301
— 862
+ 318
22
8.1
4.1
68.3
10.70
24.366
.45123
21,889
—2863
—1595
23
8.1
8.1
63.6
7.40
18.126
.02647
23,208
—6316
—5618
24
4.1
4.1
136.6
7.30
17.881
.01383
12,402
—2334
—2190
25
4 25
4.25
50
7.00
17.146
.02846
27,417
—4680
—4391
26
8.17
4.1
100.6
6.80
15.493
.01327
15,921
+1798
+2678
27
18
18
36
5.33
13.056
.01803
30,464
—1788
— 898
28
8.1
4.1
68.3
4.70
10.798
.01053
26,010
+2331
+ 69
29
8.1
8.1
63.6
3.40
8.328
.00582
24,153
—1619
—1358
h2(h + 3b) A2 , ,
: — +1 77 = — , when n.
12(h + b) 6 '
b.
In finding a formula for this set of ex-
periments, we consider only those cases
where the metal was so thick that (h-rt)
is not greater than 55.
Using Nos. 3, 4, and 27, and taking
means, we write
Nos. 3-4. No. 27. Dif . of logs.
log. (Z-+r), 1.8397859 1.1158101 0.7239758
" £ 9.5890779 8.2559957 1.3330822
1.3330822
Ratio of dif. of logs=
0.7239758
1.841335.
<l—r) 1-841335
Whence
•=.0001590065 a constant.
Q=45794
(t)
158665
;(g>
when- (Fr A) < 30, and (A-+0<55.
But when (h-^rt) exceeds 55, we find
«=t*"to(t)"
(H)
approximately. And this factor has also
been applied to the Gordon formula for
these cases.
FORMULAE FROM EXPERIMENTS ON WROUGHT IRON PILLARS. 365
III. — Hollow Cylindrical Pillars — Flat Ends.
See Stoney's Theory of Strains, page 275. &=diameter of pillar. r3=p
Excess over Q, by
h
I
I
h
e_ Q*2
Qby
experi-
No.
h
r
t
12I>2
ment.
Formulae
Formula
Gordon
ins.
I, J, K.
L.
Formula.
1
1.495
80
226.274
15
2.6441
14,673
0
—1601 f
2
1.964
60
172.816
18.8
2.4064
23,206
0
+ 894
—4588
3
2.340
51.28
145.042
10.8
1.6202
22,179
+2443
+2612
- 351
4
2.350
51
144.250
9.7
1.5733
21,572
+3098
+3246
+ 367
5
2.490
47.8
135.199
23.27
1.9357
29,798
—4582
—4666
—6547
6
1.495
40
113.137
15
1.4047
31,180
—4397
—4960
—4466
7
3.000
40
112.877
20
1.2298
27,671
— 867
—1451
— 954
8
1.964
30.5
86.267
18.8
.8693
33,299
—3935
—5420
—2034
9
3.035
29.6
83.721
18
.7430
29,789
— 128
—1709
+1913
10
4.050
29.6
83.721
29
.6745
| 27,657
+2004
+ 423
+4045
11
4.060
29.6
83.721
26.1
.6373
26.263
+3398
+1817
+5439
12
2.335
25.7
72.690
11.4
.5502
29,998
+1108
— 826
+3571
13
2.350
25.5
72.125
10.6
.5311
29,330
+1858
— 50
+4333
14
2.490
24.1
68.165
23.27
.5700
35,100
—3317
—5956
— 784
15
4.052
22.2
62.791
SO. 9
.4568
33,331
— 654
—2830
+ 1850
16
4.000
22.2
62.791
16.5
.3582
26,046
+6631
+4455
+9135
17
4.000
22.2
62.791
16
.3645
26,503
+6174
+3998
+8678
18
4.000
22.2
62.791
16.5
.3825
27,816
+4861
+2685
+7365
19
2.490
21
59.397
23.27
.1482
36,489
—3203
—5465
— 778
20
1.495
20
56.569
15
.3854
34,220
— 375
—2728
+1922
21
6.180
19.4
54.871
65
.3495
33,375
+ 819
—1570
+3019
22
6.360
18.9
53.334
49
.3558
35,985
—1462
—3766
+ 642
23
1.964
15.3
43.275
18.8
.2413
36,980
+ 59
—2609
+1015
24
3.995
15
42.426-
16.3
.1881
30,024
+7263
+4577
+8078
25
3.995
15
42.426
16.5
.2159
34,453
+2824
+ 148
+3649
26
6.366
14.1
39.881
48.9
.2313
41,664
—3593
—6336
—3249
27
2.343
12.8
36.204
11.1
.1752
38,214
+1117
—1256
+ 625
28
2.335
12.8
36.204
11.4
.1680
36,639
+2638
+ 319
+2146
29
2.335
12.8
36.204
11.4
.1623
35,389
+3942
+1569
+3450
30
2.383
12.5
35.355
9.7
.1468
33,107
+6522
+3686
+5825
31
2.343
12.3
34.790
11.6
.1684
39,569
+ 292
—2565
— 576
32
2.373
12.2
34.507
10.27
.1531
36,906
+3066
+ 187
+2125
33
6.175
9.7
28.075
61.1
.1006
38,355
+4491
— 173
+1360
34
3.000
9.3
26.305
19.6
.0905
37,392
+6403
+3105
+2420
35
4.000
7
19.799
16
.0651
47,844
+ 347
—4167
—7183
36
4.026
6.95
19.657
16
.0653
48,576
— 268
—4832
—8265
37
6.125
4.9
13.859
62.5
.0276
41,361
+12779
+3555
— 681
r
rhe Gord
on Fo
rmula hei
*e is, Q=
40960
1+* '
3000/t 2
1. Using the mean values of 8 and of
(K-r) in Nos. 35, 36, and Nos. 8, 9, 10,
11, we write,
(l~i>) 84.358 19.728
£ 0.7310 0.0652 Dif . of logs.
log. (H-?0 1.9261263 1.2950831 0 6310432
" £ 9.8639174 8.8142476 1
Ratioofdif.oflogs.=^g|=1.6634.
.00045711, a constant.
3368
£X
(t)
1.6634
Q= 131648
(r \.336«
T/ '
(I)
when (l-'rh) <S0.
2. Similarly, from Nos. 2 and 8,
11, we find, when
(l-rh)
>30
<60,
Q = 132807
(t)
',10,
(J)
3. And from 1 and 2 we derive in the
same manner,
(r \ 1.65043'
TV * (K)
(l-rh) from 60 to 80.
366
VAN nostrand's engineering magazine.
4. We may in all these cases, of course,
find values of s by interpolation, and
thence derive Q from the equation
12Er"
or Q may be derived directly by interpo-
lation.
For the case of hollow cylinders,
(l-i-h) being not greater than 60, we get
an approximate formula involving only
second differences, by the following
arrangement :
l-rh
s
D,
10
.11
.24
20
.35
.35
30
.70
.46
40
1.16
.57
50
1.73
.68
60
2.41
From which, by the " method of differ-
ences,
f=.ll + .24(n-l) + .ll("-iy-2)
IV.
n=-
'. Q:
10A'
12E€(-y-y=36,000,OO0fi(-yy. (L)
Mean value of E=27,311,lll.
Gordon formula here is
50800
Q:
1 +
3000/12
using the mean of the experimental
values of the numerator.
To find formula M we have from
Nos. 29, 28, 10, Z-+r= 111.067, £=1.28803
No. 6, l-rr- 61.609, €= .43430
log. (J-fr), 2.0455851 1.7896453 0. 2559398 =dif.
£ 0.1099260 9.6378014 0. 4721246 =dif.
t? .• **-* * i 0.4721246
Ratioofdif.oflogs. = Q2559398
= 1.84467.
1.84467
••• <(t)
Q="l«(i)
(l-i-h) from 20 to 40.
The "Phoenix Column" — Flat Ends.
See Thomas D. Lovett's Keport.
.00021701 83 a constant.
.15533
(M)
h
ins.
I
h
I
r
r*
r
12Er2
Qby
experi-
ment.
Excess over Q, by
No.
Formula
M.
Gordon
Formula.
29
28
10
6
8.250
8.250
8.125
8.050
40.7
40.7
39.9
22.4
112.4
112.4
108.4
61.6
8.935
8.935
8.935
8.536
1.4111
1.3417
1.1113
.4343
36,600
34,800
31,000
37,500
—2444
— 644
+3350
0
—3872
—2072
+7874
+6021
V. — The "American Bridge Co.'s Column" — Flat Ends.
See Lovett's Report.
Two flanged bars riveted to. the flanges of an I-beam.
h
ins.
I
h
I
r
r2
ins.
._ <#2
12Er3
Qby
experi-
ment.
Excess over Q, by
No.
Formula
N.
Gordon™"
Formula.
15
19
18
8
9.5
9.5
45
34.1
25.3
155.1
88.1
81.6
5.388
13.510
8.653
1.7394
.6591
.6398
23,700
27,800
31,500
0
+1353
—1609
— 655
+- 18
+ 312
FORMULAE FROM EXPERIMENTS ON WROUGHT IRON PILLARS.
367
Using the mean value of f for the
numerator, the Gordon formula becomes,
Q=
38600
1 + -Z-'
We find formula (N), by taking mean
values of (l-rr) and £ in Nos. 18, 19, and
combining with No. 15.
(l-~r) 155.1 84.85
£ 1.7394 .64945
1.63346
log. 1.7394 — log. .64945
log. 155.1 —log. 84.85
(r \ 1.63346
— 1 =.00045937, a constant
Ql> /rU.63346_ Q /Jy36654
/ r \. 36654
Q = 150552 (—1
(l-^rh) from 25 to 45.
(N)
VI.
-The "Keystone Column" — Flat Ends.
See Lovett's Report,
Excess over Q, by
I
h
-L
r2
c_ Q*2
Qby
experi-
No.
h
ins.
r
ins.
12Er2
ment.
Formulae
O, P.
Gordon
Formula.
27
37.6
8.625
103.5
9.798
.9088
27,800
—2564
—3177
4
35.2
9.2
98.2
10.883
.7093
24,100
+1699
+1720
26
34.6
9.375
96.9
11.178
.7880
27,500
—1556
—1607
25
33.7
9.625
95.8
11.424-
.5916
21,100
+4963
+5179
30
34.1
9.5
95.8
11.464
.8411
30,000
i —3937
—3899
31
34.1
9.5
95.8
11.464
.7122
25,400
+ 663
+ 701
24
34.1
9.5
93.4
12.041
.6650
25,000
+1353
+1101
9
20.3
8.85
64.3
7.833
.4039
32,000
— 69
— 151
7
21.7
8.3
59.3
9.206
.3222
30,000
+2035
+1312
8
20
9
55.9
10.353
.3524
36,900
' —4790
—4936
3
19.5
9.25
54.7
10.834
.2628
28,800
+3339
+3350
2
6 5
9.3
18.054
11.044
.0334
33,600
0
+2122
Gordon Formula, Q:
36225
1+;
3000 h*
using the mean value of f.
1. To find formula (O), use mean
values of [hrr) and £ in Nos. 27, 4, 26,
25, 30, 31 and 24, and in Nos. 9, 7, 8, 3.
Then (Hrr) = 97.06 58.55
£ =.74514 .33532
log. .74514-log.. 33532 _1 5798
log. 97.06— log. 58.55
i
\ i 5793
V "' =.000540995, a constant,
12E?-2 X\ I I
Q=177301 (yV~ (O)
(l~h) from 20 to 40.
2. Similarly, from Nos. 9, 7, 8 and 3,
and No. 2, we find
1.5T98
.4202
(H-r)= 58.55 18.054
s = .33532 .0334
log. .33532 — log. .0334
log.
(I)
58.55
1.96
1.96.
log. 18.054
;. 0001 15087, a constant,
QZa /^\L96
~12Er*X\T/ '
Q=37718 (- j (P)
(H-A) <25.
(See Table VII on following page.)
The Gordon formula here becomes,
44400
Q=
Z2
1+ 3000A2
Formula (R) is found as follows :
No. 22. No. 23.
(l-"rr) = 102.050 84.458
£ = .9533 .7226
368
TAN NOSTKAND S ENGINEERING MAGAZINE.
VII. — The " Square Column " — Flat Ends.
See Lovett's Report. Two Channels and Two Plates.
h
ins.
I
h
I
r
r2
ins.
12Er2
Q by
experi-
ment.
Excess over Q, by
No.
Formula
R.
Gordon
Formula.
22
32
23
7.5
9.25
8.43
41.6
30.9 •
34.1
102.050
98.096
84.458
9.347
10.909
11.628
.9533
.8867
.7226
30,000
30,200
33,200
0
+ 441
0
—1842
+3480
—1202
VIII. — Pillars with Rounded or Hinged Ends.
See Lovett's Report.
Excess over Q, by
Kind.
h
I
r2
E
Qby
experi-
No.
100000
ment.
Formula
Gordon
ins.
ins.
ins.
A.
Formula.
16
American
8
240
5.479 .
289
26,700
— 309
—1927
17
i i
10
240
8.733
231
26,500
+7122
+2371
13
"
10.75
312
8.733
304
24,000
+2301
—1602
14
a
10
312
8.733
260
22,000
+ 392
+2223
11
Phoenix
8.125
324
8.935
271
21,700
+ 444
—2315
5
Keystone
9.22
324
10.945
295
22,000
+7527
— 61
21
Square
10
309
11.000
310
25,500
+8785
—1087
.*. €
log. .9533— log. .7226.
log. 102.050 — log. 84.458
46437^ Qp
Z12E?X
=.00109037
1.46437.
Hi"
ir\'
46437
Whence Q=357350
(l-^-h) from 25 to 30.
Gordon formula here.
w
a constant.
53563
(R)
Q=
39957
1 +
,'2
1500A2
It will be noticed that formula {A),
viz.
Q=9.6E
(f)"
gives, in general, the values of Q too
large; and hence it is, in these cases,
nearer the truth than the formula above
cited as given by Weisbach, Rankine,
and Price.
Experiments, however, are wanting,
from which to derive complete formulae
for pillars.
It is evident that the method here
applied to wrought iron pillars, is equally
applicable to pillars, struts, or columns,
of any other material.
Sharpening Files. — Mr. B. C. Tilgh-
man has recently discovered another and
very interesting application of the sand-
blast to industrial purposes. He has found
that by subjecting worn files to the action
of the jet, the cutting edges are rapidly
renewed, and the file is made sharper
than when new. A stream of fine sand,
impelled at a high velocity by a jet of
steam, is applied to a file at an angle of
from ten to fifteen degrees from its face,
the file being moved about so that all
parts may be acted on. The sand is
very fine grit, prepared by washing and
settling. It is used in the state of very
soft slime, drawn from a receiver. — En-
gineeriny.
THE VENTILATION OF COAL MINES.
369
THE VENTILATION OF COAL MINES.
Bt GEORGE G. ANDRE.
Transactions of 'the Society of Engineers.
The late coal panic has shown us to
what degree our material prosperity is
dependent on that mineral. It would
seem, indeed, that the exhaustion of our
coal fields must inevitably be followed
by the utter collapse of those industries
which have made this country what it is,
and that even a slightly decreased pro-
duction would seriously affect their posi-
tion. Coal having assumed a relation of
such vital importance to our social exist-
ence, its extraction from the earth has
become one of the foremost engineering
questions of the day. and accordingly
increased attention is now being directed
to it. The author of the present paper
has therefore deemed the time opportune
for a discussion of some of the facts
relating to what is certainly one of the
most important subjects of mine engi-
neering, namely, the ventilation of the
workings. One of the effects of the
recent panic may be seen in the greater
activity shown at existing collieries as
well as in the opening out of many new
ones. In their haste to extract the
valuable mineral there is danger that
managers and engineers may not give
due attention to those matters which are
essential to an efficient ventilation, es-
pecially in the laying. out of new works.
Hence another reason for calling atten-
tion to the subject at this time. More-
over it is almost an indisputable fact
that 90 per cent, of those disastrous
explosions which so frequently occur are
wholly due to a defective ventilation.
Thus it appears that though the princi-
ples of a good ventilation are generally
understood and acknowledged in theory,
they are still far from being applied in
practice. By the expression "defective
ventilation," it is not intended to mean
merely insufficient ventilation, but also
all systems of ventilating a mine that are
established upon false principles, quite
irrespective of the quantity of air pass-
ing through it in a given time. Of
course it is quite impossible to treat so
large a subject in a paper like the pres-
ent, and therefore no such attempt will
be made. All that the author proposes
Vol. XIX.— No. 4—24
I to do is to direct attention to a few
essential points, and instead of adducing
I anything new, to simplify what is
! already known.
It is agreed on all hands, and Parlia-
: ment has recently enacted, that a suffi-
I cient quantity of air should be constantly
passed through a mine to dilute and
render harmless the noxious gases evolv-
ed or generated therein. But there
does not appear to be any definite
understanding among mining men as to
what constitutes a sufficient quantity,
and the practice among careful men is to
pass an excess of air in order to be on
the safe side. No doubt this is erring in
the right direction; but it is better not
to err at all. Besides, such a practice
begets a vagueness of notion concerning
the requisite quantity of air that con-
duces neither to correctness of judgment
nor to progress in knowledge. It may
in some cases be a source of danger
even, for a Davy lamp is not safe in a
violent current of air that has been sud-
denly fouled by a blower, while the cost
of producing the current is enormously
increased. Of course the question is an
intricate and a difficult one, depending
upon numerous conditions that vary
| from district to district, and even from
j mine to mine. A general solution is
therefore not to be looked for; but it is
both practicable and highly desirable to
lay down some definite and invariable
j basis upon which every individual case
I may be accurately and readily calculated.
The atmosphere of a coal mine is
vitiated by several causes: the breath of
men and horses, the combustion of lights,
the moisture of the ground, the exhala-
tion of gases from the strata, and the
chemical changes which are constantly
going on in the substances exposed to
the influence of the air. Some of these
causes are constant in their action or
nearly so, while others are extremely
variable. The former we can estimate
with accuracy; with the latter we can
deal only approximately.
The average quantity of air breathed
by man is usually assumed by writers
370
VAN nostrand's engineering magazine.
on mine ventilation to be 800 cubic feet
per minute. This quantity is, however,
altogether erroneous as a basis on which
to calculate an adequate amount of ven-
tilation. It has been stated by eminent
medical authorities that the mean of
several hundred experiments conducted
with great care by means of very accur-
ate instruments was 502 cubic inches per
minute, and that this quantity was
increased to 1500 cubic inches, or nearly
three times as much, by the exertion of
walking four miles an hour. "We all
know from experience that a much
larger quantity of air is breathed when
undergoing violent exercise than when
at rest ; and we cannot therefore found
a calculation relating to men subjected
to great physical exertion in a mine upon
what has been ascertained respecting a
man lying motionless on his bed. It
may be assumed that the average amount
of labor undergone by each man and boy
in the extraction of coal is at least equal
to that of walking four miles an hour;
and hence the quantity of air required
for each man will be 1500 cubic inches,
or say, one cubic foot per minute. The
miasmata or effluvia derived from the
various secretions of the body are a
potent cause of vitiation in the atmos-
phere. The unpleasant smell of a close
bedroom in the morning is due wholly to
this cause, and in ascertaining the state
of ventilation in a room by what is
known as the "nose test," it is these
effluvia which furnish the requisite indi-
cations. Moreover the air in passing
over the human body becomes heated.
These causes are greatly increased in
intensity by the augmented temperature
due to violent exertion, such as is under-
gone in mines. Added to this there is
the dust caused by each workman float-
ing in the atmosphere. We must
therefore provide an additional quantity
of air to keep the atmosphere pure and
cool, and this quantity may be taken as
one cubic foot per minute. This allows
a covering or film of air over his whole
body about -f inch thick, which film is
changed every minute. Each man's
lamp will heat the air and foul it with
the products of combustion to a degree
requiring about one cubic foot per min-
ute. Thus the quantity of air requisite
per man will be three cubic feet per
minute. A horse fouls about six times
as much as a man, and will therefore
require twelve cubic feet per minute.
The foregoing may be considered the
constant causes of vitiated air, and are
easily dealt with. We come now to con-
sider the varying causes, namely, the
moisture of the ground and the gases
evolved. It is impossible to treat these
otherwise than approximately, but an
approximation sufficiently near for prac-
tical purposes may be arrived at. The
gases existing in a coal mine are chiefly
carbonic acid or choke-damp and carbu-
retted hydrogen or fire-damp. Other
gases are generated, but in such small
quantities that their presence is not of
much importance, except perhaps when
blasting is extensively practiced. These
two gases, carbonic acid and carburetted
hydrogen, are continually being exhaled
in greater or less quantities from the
face of the exposed strata, and therefore
the total quantity is to a certain degree
dependent on the extent of surface ex-
posed. They are given off more abund-
antly from fissures, especially in the
neighborhood of faults. Considerable
quantities of carbonic acid are also in
every mine due to the respiration of men
and horses, the combustion of lights and
the deflagration of gunpowder, all of
which causes are subjects of calculation.
In smaller quantities, carbonic acid is
formed by the fermentation and decom-
position of vegetable matter.
When the proportion of carbonic acid
to the atmospheric air reaches TVth the
compound will not support combustion,
and is fatal to life. A proportion of -j^th
of carburetted hydrogen renders the
compound inflammable. These propor-
tions may be taken as the limits which
must never be reached; or, to further
simplify the matter, the proportion of
pure atmospheric air must, in a mine,
never be less than ^§- ths of the total vol-
ume therein contained.
The question now is what quantity of
air in a dry mine, making but little gas
of any kind, is sufficient, irrespective of
the respiration of men and horses, to en:
sure this proportion under all conditions.
This problem, as we have said, can only
be solved approximately, but as it is
mainly a matter of experience and calcu-
lation, a fairly close approximation may
be arrived at. A careful investigation
of this matter has led the author to con-
THE VENTILATION OF COAL MINES.
371
elude that one cubic foot of air per sec-
ond for every 100 square yards of sur-
face is an adequate quantity. This al-
lows for the exhalation and formation of
.067 cubic foot of impurities, that is,
noxious gases, watery vapor, and solid
floating matter per second. In other
words, one cubic foot of air per 100
yards of surface is equivalent to a film
about f inch thick spread over that sur-
face, which film is changed every minute.
And .067 cubic foot of gases to the
same extent of surface is equivalent to a
film about -£$ inch thick formed every
minute. Of course the gas is not ex-
haled in this regular way over the whole
surface exposed. But the quantity here
given is approximately that which is
given off -the surface at the worst parts
under the conditions previously men-
tioned.
This quantity of one cubic foot per
second for every 100 yards of surface
may be taken as a reliable basis upon
which to calculate an adequate ventila-
tion. It must be borne in mind that the
quantity is only just sufficient under the
very favorable conditions which we have
assumed, and is, therefore, analogous to
the breaking strain of materials. In
every case it will have to be multiplied
by an appropriate factor of safety, the
value of which must be determined by
the conditions of the case. All mines
are, in a greater or less degree, liable to
give off " blowers," that is pent-up accu-
mulations of gas which are liberated
by the boring and driving, or by falls of
roof. The gas issues from the blowers
with a sound resembling, in the smaller
ones, the simmering of a teakettle, and
in the larger that of blowing off high-
pressure steam. Of course it is quite im-
possible to estimate the value of these
blowers with anything like accuracy, just
as it is impossible to estimate the value
of the strain to which a structure exposed
to sudden shocks may be subjected. In
both cases a sufficiently large factor of
safety must be taken to include possibili-
ties and to leave an ample margin of
safety. It may be remarked that no
system of ventilation can be calculated
for the large blowers previously men-
tioned. They are fortunately of rare oc-
currence, and when one does occur, the
only practicable plan is to call out the
men until it has exhausted itself. When
their presence is suspected, safety lamps
alone should be used. The small blowers
are more constant in their action, and
are capable of being estimated with some
degree of precision.
Besides varying in gaseous products,
mines differ in degree of moisture. Blast-
ing is also more extensively practised in
some mines than in others. All of these
circumstances will influence the factor of
safety, the value of which must be de-
termined for every individual case, and
which will vary from 2 to 6. Let us now
apply these principles to an example.
Suppose we- have to ventilate a mine in
which the air-courses have a total length
of 2000 yards, giving a total surface of,
say, 14,000 square yards; and, to sim-
plify the calculation, we will suppose
that the number of men and horses are
100 and 10 respectively. Respiration,
perspiration, and lamps will then require
100 X 3 + 10 X 12=420 cubic feet per
minute; and the gases, vapors, &c, will
need 1^gg° = 140 cubic feet per second =
8400 cubic feet per minute. Supposing
the mine to generate but little fire-damp
and to be not particularly wet, we may
take the factor of safety at 3, which will
give (840° + 420) X 3 = 26,460 cubic
feet per minute as the adequate amount
of ventilation. In this case we have
taken the surface and the factor of
safety for the entire mine; but when, as
it usually is, the mine is divided into
several districts, which are aired by
separate currents, the air must be appor-
tioned according to the surface of each
district and the factor of safety determ-
ined by the nature of the seam or the
conditions of the workings. Thus the
factor of safety may vary from district
to district.
When the proper quantity of air has
been determined, the next question is,
how to get it through the workings.
One mode of effecting this is to provide
contracted air-ways and to give the ven-
tilating current a high velocity. An-
other is to have spacious air-ways and a
low velocity. For economical reasons,
the former is but too frequently adopted.
In many cases a drift is driven with an
insufficient sectional area; in other cases,
falls of roof, the creep of the floor, and
other causes reduce the dimensions of an
air-passage to those of a mere creeping
hole. Fully 25 per cent, of the air-
372
van nostrand's engineering magazine.
courses in collieries which are now being
worked, and in which the ventilation is
said to be perfect, can only be entered
by a man in a crawling posture. The
economy of a system that lays out works
in such a manner, or that allows them to
get into such a condition, is more than
doubtful. The drag of the air, that is-,
its retardation by contraction and fric-
tion, is enormously increased thereby,
and the consumption of fuel in the fur-
nace, or in the engine when a mechanical
ventilator is used, is augmented in a
like proportion. But even when the ad-
ditional cost of fuel is incurred, the
friction with small passages and high
velocities is so great that it is impossible
to ensure sufficient ventilation at all
times, and hence there is the constant
risk of accident, with its accompanying
danger to life and property. It may
therefore be laid down as one of the es-
sential principles of an efficient ventila-
tion, that spacious air-ways are indispens-
able. A limit that may be adopted with
advantage is, that all air-ways other than
shafts should allow a sufficient quantity
of air to pass with a velocity not exceed-
ing 6 feet per second.
Another important fact connected with
the dimensions of air-ways is, that the
return passages require a larger sectional
area than the intake passages. When
the ventilating current enters the return
ways from passing through the workings,
it is laden with the various gases that
are generated in a mine, watery vapor,
the solid products of combustion and
coal dust, and its temperature, and con-
sequently its bulk, is considerably in-
creased. Thus it has lost a great part of
its elasticity and it drags more heavily.
To compensate this, its friction should be
lessened by increasing the sectional area
of the passage. To ensure a proper
state of ventilation there should be two
return ways, each equal in sectional area
to the intake. As far as practicable, the
air-courses should have at all parts of
their length the same sectional area. It
is, perhaps, hardly necessary to remark
that they should be kept free from all
obstructions, such as projecting pieces of
timber or stones.
One of the most effective means of di-
minishing the friction is to shorten the
runs by dividing the workings into dis-
tricts and ventilating each with a sepa-
rate air-current. Thus, a shaft 12 feet
in diameter will afford sufficient area for
five different air-ways each of 20 feet
area. This system of splitting the air,
as it is called, though well-known, is not
adopted so extensively as it ought to be.
There are many mines in which the old
unwholesome and dangerous practice of
passing the air through in one column
from the downcast to the upcast shaft
still prevails, though the evils attending
it have long been acknowledged by the
majority of viewers. An additional and
great advantage possessed by the system
of ventilating by districts is that of con-
fining the effects of an explosion to a
small part of the workings. In all cases
of splitting the air, the split should be
made as near the downcast shaft, and
the several branches reunited as near the
upcast as possible, and the air-ways be-
tween the shafts and the points where
the branches separate and reunite should
have a large sectional area.
The distribution of the air through the
workings requires great skill. There are,
indeed, few matters connected with
mining that test the skill and ability of
the engineer more than this. A very
slight variation in the direction of the
ventilating current may make all the dif-
ference between a good and a defective,
and consequently a dangerous ventila-
tion. And yet this important duty is
often left to ignorant hands. No doubt
the men who are entrusted with this im-
portant work are experienced men, and
men who on that account would be called
practical. But there are things which ex-
perience alone cannot teach, at least in
the lifetime of a single individual. A
certain amount of scientific knowledge
and an acquaintance with collateral sub-
jects, such as the composition of gases,
the nature of fluids, and the laws which
they obey, are absolutely necessary to
enable a man to manage efficiently the
ventilation of a mine. And such know-
ledge is part of a liberal education.
The essential conditions of a good
distribution are : (l) That the air shall
not pass from the broken to the whole
workings; and (2) that an explosion
shall not take the air off the men at the
faces of work, or reverse its direction.
The author does not hesitate to assert
that three-fourths of the explosions that
occur, and that result in such a lamenta-
THE VENTILATION OF COAL MINES.
373
ble destruction of life and property, are
caused solely by the neglect of the former
of these conditions, and are therefore
preventable; and that a large proportion
of the deaths that result are due to the
neglect of the latter conditions; for in
most cases fewer men are killed by the
direct effects of the explosion than by
the after-damp. It does, indeed, seem
strange that such an ignorant mode of
distributing the air should still be com-
monly adopted. When the ventilation
is in uneducated hands we may attribute
the practice of the pernicious system to
ignorance and want of skill; but when,
as is sometimes the case, we find the
practice perpetuated under the authority
of men eminent in their profession, we
are forced to believe that a criminal
economy is at the bottom of the matter.
The second condition is scarcely of
less importance than the first, as it deals
with the effects of an explosion should
such an accident occur from any unfore-
seen cause. The ventilating current will
always take the shortest course to the
upcast shaft. If, in consequence of an
explosion, the doors or stoppings are
injured, a large portion of the workings
may be left entirely without air at a
time when it is most needed, namely,
when the passages are foul with the
after-damp or carbonic acid gas produced
by the explosion. To prevent such an
occurrence the distribution should be so
arranged as to preclude the possibility
of the current of air being diverted from
its proper course before it has left the
working places, or of being stopped
altogether by an injury to the return
passage. All permanent stoppings
should be built of brick or stone and
well plastered; they should also be well
backed, especially those by the side of
the main ways, which should have five
or six yards of stowing behind them.
Whenever a crossing is necessary for the
return it should, if possible, be by a
stone drift over or under the main way.
The additional cost thus incurred would
be more than compensated by the addi-
tional security obtained. Were all these
precautions duly observed, mining would
be freed of half its perils. A strict
supervision would be all that was neces-
sary to protect the mine against the
danger of an explosion occasioned by
any but unforeseen causes. Such super-
vision is indispensable in all cases to
ensure the proper quantities of air being
apportioned to the several districts, and
the needful precautions constantly taken
I to maintain a steady uniform current of
I air. Without this the best system must
J prove ineffectual.
DISCUSSION.
Mr. Baldwin Latham said he would
offer a few remarks in order to open the
discussion, but his observations would
! be on the general question of ventilation
' rather than with particular reference to
I coal mines. He had certainly given
some attention to the ventilation of coal
I mines when studying the # ventilation of
\ sewers; but he had found that the
! system of having one downcast and one
i upcast shaft for the ventilation of coal
| mines was comparatively easy to carry
| out, but that it was not at all applicable
I to sewers. From his examination of a
! large number of coal mines he was con-
I vinced that the observations which had
been made by Mr. Andre in his paper
were of very great value. The paper
did not touch upon the particular means
which were adopted for the ventilation
of coal mines, but it simply brought for-
ward broad facts which it would be well
for all interested in such matters to bear
in mind, and which showed that there
never could be safety without a super-
abundance of fresh air. There was not
sufficient attention paid to the ventilation
of a mine as the workings were worked
out, or as the material was extracted.
In his opinion a new mine required far
less air than one which had long been at
work. The little passages which were
shown in the diagrams were air-channels;
and in a new mine the cubic capacity of
those channels would be comparatively
small ; but when the mine was worked
out the cubic capacity became greater.
When gases escaped or blowers occurred,
the passages and goaves acted as gas-
holders by means of which gas could be
accumulated. In an old mine the same
intake and the same volume of air passed
through it as in a new mine, although
the cubical capacity in the old mine was
greater. The chances were that in old
mines the whole area might become oc-
cupied with gas which, by the admix-
ture of the atmospheric air, in limited
quantities, would be rendered explosive.
374
VAN NOSTEAND'S ENGINEEKING MAGAZINE.
Instead of being diminished as the mine
was worked out, and the cubical capacity
of the mine became greater, the amount
of air ought to be increased, and not
only so, but adequate mechanical ar-
rangements ought to be introduced by
which the air could be conducted
through the vacant spaces so as to com-
pletely ventilate the mine.
It was a disputed point whether natu-
ral or mechanical means ought to be
adopted for ventilating mines. By
mechanical means, he meant the use of
steam as a mechanical power, for either
driving air into the mine or sucking air
out. The plan of driving air into a mine
was called the plenum system, and the
plan of drawing air out was called the
vacuum system. The natural system of
ventilation consisted of those methods in
which the air of a mine was heated by
ordinary combustion, so that they got a
column of heated atmospheric air which
was considerably lighter than an equal
column of cooler air, and by this differ-
ence in the weight of respective columns
of air motion was produced. Air upon
being heated dilated ^^j-tli of its own
bulk for every degree Fahrenheit. Hence
he fully corroborated the statements of
Mr. Andre, that the passage for the
exhausted air required to be far larger
than the passage for the intake air. Air
always passed into a mine at a tempera-
ture far lower than that of the air some
hundreds of yards below the surface of
the earth. The air of a furnace was
applied in order to heat air in excess of
atmospheric heat, and create that current
of air which is necessary to aerate every
part of the mine. A cubic foot of air
heated 50 or 60 or perhaps 80 degrees
would occupy a far larger space than it
originally occupied when it entered the
mine. This caused the necessity for
increasing the size of the air-passage for
all air which had once passed through
the mine. If this was not done there
would be a contraction, and contraction
meant waste of force, and it also meant
retardation of ventilation. Further, it
was possible when there was a contract-
ed passage that from some sudden cause,
such as the explosion of gunpowder in
the mine, the whole current of ventila-
tion might be changed in the opposite
direction. Therefore it was needful in
all cases of mine ventilation to make the
passage of the air as easy as possible,
from the place where it entered to the
place where it passed out. If the pas-
sages were uniform throughout, some
circumstances might momentarily change
the direction of the air, and the result to
those who were laboring in the mine
might be an immense loss of life.
Hence the necessity of producing en-
larged passages for the easy exit of the
air that had been used in the mine. Air
would always take the shortest passage.
We might make passages for it, but it
would not follow the route prescribed
for it if it could get away by any shorter
cut.
THE DISTRIBUTION OF AMMONIA.*
By Dr. R. ANGUS SMITH, F. E. S., &c.
From " Journal of the Society of Arts."
If organic matter is everywhere, am-
monia is everywhere possible, and if that
matter is decomposing, ammonia is
everywhere. This is the general state-
ment which this paper illustrates. It is
now many years since it was observed by
me that organic matter could be found
on surfaces exposed to exhalations from
human beings; but it is not till now that
the full significance of the fact has
* Paper read before the Manchester Literary and Philo-
sophical Society.
shone on me, and the practical results
that may be drawn from it in hygiene
and meteorology. These results are the
great extension of the idea that ammonia
may be an index of decayed matter; the
idea itself has been used partly and to a
large extent, as illustrated in my " Air
and Rain." The facts now to be given
enable us to claim for it a still more_ im-
portant place. The application seems to
fit well the conditions already examined,
and by this means currents from fou
THE DISTRIBUTION OF AMMONIA.
375
places have been readily found. This
does not apply to the substances which
may be called germs, whether it be
possible to see them or not, because
these are not bodies which have passed
into the ammoniacal stage, although
some of them may be passing; those, for
example, which are purely chemical, and
exert what we may call idiolytic action.
This word may serve to mark this pecu-
liar action, which was left by Liebig un-
named; he used the vague term invented
by Berzelius, namely, catalytic. I have
elsewhere recognized the two classes of
germs, instead of any disputed one, with-
out naming them.
It is now many years since Liebig first
surprised me by saying that iron ores
and aluminous earths were capable of
taking up ammonia, and if they were
breathed upon we were able even to
smell that substance. He, much about
the same time, made numerous experi-
ments, in order to find the ammonia of
the atmosphere, and to measure its
amount in raiu. The result for science
was great, and Professor Way continued
the inquiry for the Royal Agricultural
Society. Dr. Gilbert, F.R.S., amongst
his many labors in the department of
agricultural science, has made this inquiry
into ammonia of rain in still later times;
but I shall not at present quote his re-
sults, as this paper does not intend to go
fully into the subject, but rather to indi-
cate its magnitude and importance. The
first paper I ever read to this Society was
on the ammonia found in peat : I was
unable then to see the extent of the sub-
ject.
I shall give parts of the fuller paper
without the long tables of results.
Ammonia must ever be one of the
most interesting of chemical compounds.
It comes from all living organisms, and
is equally necessary to build them up.
To do this, it must be wherever plants or
animals grow or decay. As it is volatile,
some of it is launched into the air on its
escape from combination, and in the air
it is always found. As it is soluble in
water, it is found wherever we find
water, on the surface of the earth or in
the air, and probably in all natural waters,
«ven the deepest and most purified. As
a part of the atmosphere it touches all
substances, and can be found on many;
it is, in reality, universally on the sur-
face of the earth, in the presence of men
and animals, perhaps attached, more or
less, to all objects, but especially to all
found within human habitations, and, we
might also add, with equal certainty, the
habitations of all animals.
If you pick up a stone in a city, and
wash off the matter on the surface, you
will find the water to contain ammonia.
If you wash a chair, or a table, or any-
thing in a room, you will find ammonia
in the washing; and if you wash your
hands, you will find the same; and your
paper, your pen, your table-cloth, and
clothes, all show ammonia, and even the.
glass cover to an ornament has retained
some on its surface. You will find it not
to be a permanent part of the glass, be-
cause you require only to wash with pure
water once or twice, and you will obtain
a washing which contains no ammonia.
It is only superficial.
This ammonia on the surface is partly
the result of the decomposition of organic
matter continually taking place, and ad-
hering to everything in dwellings. The
presence of organic matter is easily ac-
counted for, but it is less easily detected
than ammonia. It is probable that the
chief cause of the presence of ammonia
on surfaces in houses, and near habita-
tions, is the direct decomposition of or-
ganic matter on the spot. If so, its
presence, being more readily observed
than organic matter itself, may be taken
as a test, and the amount will be a meas-
ure of impurity. A room that has a
smell indicating recent residence will, in ,
a certain time, have its objects covered
with organic matter, and this will be in-
dicated by ammonia on the surface of
objects. After some preliminary trials,
seeing this remarkable constancy of com-
parative results and the beautiful grada-
tions of amount, it occurred to me that
the same substance must be found on all
objects around us, whether in a town or
not; I, therefore, went a mile from the
outskirts of Manchester, and examined
the objects on the way. Stones that not
twenty hours before had been washed by
rain showed ammonia. It is true that
the rain of Manchester contains it also;
but, considering that only a thin layer
would be evaporated from these stones,
it was remarkable that they indicated the
existence of any. The surface of wood
was examined — palings, railings, branches
376
VAN NOSTRAND'S ENGINEERING MAGAZINE.
of trees, grass (not very green at the
time), all showed ammonia in no very-
small quantities. It seemed as if the
whole visible surface around had ammo-
nia. I went into the house and examined
the surfaces in rooms empty and in-
habited, tables, chairs, ornaments, plates,
glasses, and drawing-room ornaments.
A (Parian) porcelain statuette, under a
glass, showed some ammonia; a candle-
stick of the same material (but uncovered)
showed much more; .the back of a chair
showed ammonia, when rubbed with a
common duster, very little. It seemed
clear that ammonia stuck to everything.
If, then, ammonia were everywhere,
the conclusion seemed to be that it was
not at all necessary to do as I had been
doing, namely, wash the air so labori-
ously; it would be quite sufficient to sus-
pend a piece of glass, and allow the
ammonia to settle upon it. For this
purpose small flasks were hung in
various parts of the laboratory, and they
were examined daily. The flasks would
hold about six ounces of liquid, but they
were empty, and the outer surface was
washed with pure water by means of a
spray bottle; it was done rapidly, and
not above 20 c.c. (two-thirds of an
ounce) of water was used. This was
tested for ammonia at once with the
Nessler solution. The second washing
produced no appearance of ammonia,
done immediately. Ammonia could be
observed after an hour and a half's expo-
sure, at any rate, but I do not know the
shortest period. The results of the
washings were as follows; they are the
average of 34 experiments for some, and
17 for others; in all 238 experiments:
Front laboratory.
Second landing. .
Balance-room
First landing
Back laboratory.
Entrance lobby. .
Office
Back yard
Back closet
Midden
Height
from
floor.
ft. in.
7 3
0
1
10
5
5
7
Am-
monia
M.gms
0.013
0.032
0.015
0.007
0.010
0.007
0.003
0.036
0.105
0.572
H^tj Am-
floo™. H ia
ft. in. M.gms
o,
4
0 8
0 6
0.019
0.009
0.010
0 7 ! 0.042
The first three belonging to the work-
ing laboratory are not very regular, as
we might suppose, but they never rise
very high, nor do they sink to the lowest.
The rest, except the second, keep a re-
markable similarity, and the differences
are very great. In the second there is
a disturbance caused by sweeping the
floors. On the other days it was
requested that everything should be
kept still. This of course brings in a
practical difficulty, and limits the use of
the test to cases where care can be used
and thoughtful observation, since there
are many ways by which dust may be
made to interfere, even although the act
of sweeping should not take place. The
house experiments gave similar grada-
tions.
The result seems to be that a piece of
glass, of a definite size, hung up in any
place, will receive deposits of ammonia,
or substances containing ammonia, in a
short time; and by washing the ammonia
off with pure water, and testing it with
a Nessler solution, it may be seen whether
there is too much or not. It is the sim-
plest test for ammonia yet found. Its
discoverer deserves great thanks. It
must not be forgotten that we may have
ammonia in very different conditions; it
may be pure, or it may be connected
with organic matter. This mode of in-
quiry is better suited as a negative test
to show that ammonia is absent, than to
show what is present. When ammonia
is present there may be decomposing
matter; when absent there is not. I am
hoping to make this a ready popular test
for air — a test for sewer-gases, for over-
crowding, for cleanliness of habitations,
and even of furniture, as well as for
smoke and all the sources of ammonia.
Of course it must be used with consider-
ation, and the conclusions must not be
drawn by an ignorant person.
How far it may be used as a test of
climate is a matter to be considered.
After this I made another series of
trials with air. Nesslerising the wash-
ings at once, and not after laborious dis-
tillings, as in former cases; the results
are very valuable, showing that we ob-
tain comparative quantities in this way.
The amount of ammonia obtained in
this ready way does not give exactly the
same results as the more laborious
methods which I have used, but it may
be taken as the most convenient. It
must be observed that the amount rises
REPORTS OF ENGINEERING SOCIETIES.
377
exactly where you might expect more
organic matter to exist. The lowest is
from Prince's road, outside the town, and
almost half a mile from the extreme of
the Manchester houses. The next is
obtained from an empty yard behind my
laboratory, but it is still pure because
there was wind and rain; and any one
who observes how unusually pleasant it
is to breath air even of a smoky town
during wind and rain will not be sur-
prised. I have not yet, however, had
the purest air. I shall require to make
a campaign on the moors, hills and seas,
before I can give numbers for this. I
have not even obtained the best given
on land at a distance from manufactures.
All this will be done in time.
In my office the amount is larger than
outside, but the air is not so bad as it is
in front, and not so good as sometimes
in the front where it is open. From the
back of the laboratory, during fog, the
ammonia was much higher, but during
one day it was excessive, and a special
examination of it was made in several
streets. The highest amount Was ob-
tained at the front of the Cathedral,
about midday, on the 8th of February,
1878, when the amount was 1.25, or 14^
times more than it had been found in
Prince's Road, showing a considerable
range:
M.grms. of ammonia per
per cubic meter of air.
Prince's Road 0.086
Open yard during rain 0.119 and 0 . 102
Front of laboratory 0.167 ordinary
Office 0.167
Front and back during fog . 0.476
Close shut up room 0.413
Closet outside 0.800 to 0.900
Densest part of fog 1 .25
in France. It consists of nine sections, which
are as follows :
Section 1. Mines and Metallurgy. — 1. Steel :
New Modes of Making Steel ; 2. Explosions
of Firedamp ; 3. Transport in Working-
Mines ; 4. Mechanical Working of Coal ; 5.
Process of Sinking Wells and Shafts.
Section 2. Agriculture and Rural Engineering,
—1. Steam Culture ; 2. Utilizing Hydraulic
Resources ; 3. Reclamation of Land fit for
Cultivation ; 4. Machines serviceable for Har-
vesting ; 5. Economical Transport in Farms.
Section 3. Machines.— 1. Steam Power ; 2.
Accumulators ; 3. Associations for Supervision
of Steam Engines ; 4. Unification of the
Dimensions of the Parts of Machines; 5.
Choice of the Fittest Metals to adopt for the
different Parts of Machines.
Section 4. Roads, Rivers, and Canals.— 1.
Inundations : Means of Checking them ; _ 2.
New Descriptions of Metal Bridges ; 3. Utili-
zation of Roads and Banks for the Establish-
ment of Railways ; 4. Comparison of the
Different Modes of Paving Towns ; 5. Dams
for Rivers.
Section 5. Railways— 1. Economical Rail-
ways ; 2. Motor Machines for Tramways ; 3.
Material Improvements to Introduce into the
| Passenger Service ; 4. Perfecting the Way ;
5. Employment of Steep Gradients.
Section 6. Navigation, Fluvial and Maritirne.
— 1. Compound Engines in Marine Naviga-
tion ; 2. Resistance of Hulls ; 3. Haulage of
Boats : Life-boats ; 5. Rolling and Pitching.
Section 7. Public and Private Constructions. —
1. Supply and Distribution of Water in
Towns ; 2. Drains ; 3. Ventilation of Edifices ;
4. Mechanical Perforation of Galleries and
Tunnels ; 5. Foundations of Great Works.
Section 8. Industrial Physics and Chemistry.—
1. Utilization of Artificial Cold : 2. Lighting
large Workshops ; 3. Pneumatic Telegraphs ;
4. Industrial Employment of Explosive Sub-
stances ; 5. Gas Stoves.
Section 9. Different Industries. — 1. Machines
for Domestic Use ; 2. Fabrication of Paper,
from the point of view of the Paucity of
Rags ; 3. Recent Progress of Spinning and
AVeaving ; 4. Cements, their Manufacture and
Use ; 5/ Character of Textile Fabrics, ja
REPORTS OF ENGINEERING SOCIETIES.
American Society of Civil Engineers. —
The papers published by the Society in
the "Transactions" since our last issue are :
No. 159. On the Theoretical Resistance of
Railway Curves, by S. Whitney.
No. 160. On the Cause of the Maximum
Velocity of Water Flowing in open Channels
being Below the Surface, by James B. Francis.
No. 161. The Flow of Water in Pipes under
Pressure, by Charles G. Durragh.
International Congress on Civil Engi-
neering.— The programme of the Inter-
national Congress on Civil Engineering at Paris,
in 1878, is of importance not only as a guide to
inquiry and discussion, but as a synoptic view
of that branch of practical science as regarded
IRON ANQ STEEL NOTES-
Messrs. Hoopes & Townsend, manufacturers
of iron bolts, nuts, rivets, etc., have
issued a pamphlet which contains much valu-
able information. It is largely made up of
reports by Professor Thurston on tests made
under his supervision upon cold punched and
, hot pressed nuts.
The results are beautifully tabulated and the
! reports are illustrated by cuts of the first order
I of excellence.
The paper on the flow of metals by Tresca is
I added with illustrations. This paper explains
I how in cold punching the strength of the
I metal is preserved.
The exhibit at the Centennial of this cele-
I brated firm proved the excellence of their
I method.
378
VAN NOSTRAND'S ENGINEERING MAGAZINE.
IMPROVEMENT IN THE MANUFACTURE OP
Steel. — The following description of an
improvement in the manufacture of steel has
been sent to the "Bulletin of the American
Iron and Steel Association" by Mr. W. Dough-
erty of Cedar Lake, New Jersey, the patentee.
"Steel cast by the ordinary process is rarely
free from seams, soft places, honeycomb, &c,
thereby causing considerable loss to the manu-
facturer or purchaser. The object of my in-
invention is the production of steel free from
defects. The invention relates to the casting
of the ingots in sheet metal moulds or cases of
such thickness as will be brought to a welding
heat without chilling the surface of the ingots, so
that the steel and case may cool and shrink
simultaneously, and the case become thereby
welded to the steel, and thus exclude the at-
mosphere from the latter and thereby prevent
such imperfections as result from the shrink-
ing away of the steel from the mould. I make
the case of any form or size the ingot is re-
quired to be, taking care not to have the sheet
out of which it was formed of greater thickness
than will be brought to a welding heat without
cooling the surface of the melted steel when
poured into it, so that the case and ingot may
cool simultaneously and a complete welding
be produced. The sheets of which the cases
are formed should not be too thick, otherwise
a welding will not take place, and the thick-
ness should vary according to the size of the
case; consequently, for casting small bars of
steel, say two or three inches in diameter, the
thickness should not be more than the sixteen-
wire gauge. The steel thus encased when put
into the furnace for heating, having its surface
completely protected from the atmosphere, re-
tains the carbon in its imperfect places as well
as in the solid parts of the metal, and conse-
quently, when subjected to the action of the
rolls or hammers, a complete welding of the
metal is produced, and a homogeneous mass of
the metal is the result. A portion of the
metal case or mould is burnt or wasted away
during the process of heating the steel. The
remainder, being thin, is taken off, or nearly so
in the working of the metal, so that no incon-
venience results from the steel being encased.
In the usual method of casting ingots in thick
cast iron moulds the moulds chill the surface
of the ingot, causing a deep hole in the upper
end, which is technically called piping. This
occasions the necessity (ff breaking off the
end of the ingot, and thus causes a loss of from
ten to twenty five per centum of the steel. In
casting by my process, the mould or case, be-
ing thin, does not cool the melted steel, and
being brought to a welding heat by the latter,
as above specified, the steel cools slowly and
uniformly with it closing in to the centre of
the ingot, and thus avoiding the piping inci-
dental to the usual mode of casting in thick
moulds. I claim as my invention the method
of casting steel in wrought iron or other me-
tallic cases when the latter is of such thickness
as to admit of the heat of the melted steel com-
pletely welding the case to it, substantially as
and for the purpose above set forth."
The Preservation op Iron Surfaces. —
Mr. George Bower, of St. Neot's, has
lately perfected a process for coating iron with
the magnetic oxide, not however by means of
superheated steam, but by the employment of
heated air. Mr. Bower conceived the idea that
the oxygen as it exists in the atmosphere would
serve the same purpose equally as well as, if
not better than, the oxygen as it exists in
water or steam. He therefore made some
elaborate experiments which conclusively
proved his supposition to be correct.
Having satisfactorily established this fact
Mr. Bower experimented on a large scale, and
at length succeeded in giving practical shape
to his process. During his experiments Mr.
Bower had an idea that the hot blast as used in
the production of pig-iron would not only
heat iron exposed to it to the required tem-
perature, but that it would at the same time
supply the oxygen for the formation of the
magnetic oxide. By the courtesy of Messrs.
Cochrane, of Dudley, he was enabled to prove
this. A bar of iron of square section exposed
to the action of the hot blast for about twelve
hours was found to be thoroughly coated with
the magnetic oxide. This coating, it is stated,
has perfectly resisted the oxidising action of
moist air under the most trying conditions.
The method of procedure in practice is to ex-
pose the iron articles in a retort or chamber,
the temperature of which is raised to a point
dependent upon the ultimate use to which
the articles are to be put, and which ranges
between a dull and a bright red heat. Air is
then introduced and imprisoned in the cham-
ber, a fresh supply being fed in at stated
intervals. The articles under treatment are
exposed to the combined, influence of heat
and air for periods which vary according to
the nature of the objects, the result being the
formation upon them of the protective coating
of magnetic oxide.
In carrying out the process at his works Mr.
Bower uses an iron chamber which is built
into a furnace; it is, in fact, set very much in
the same way as gas retorts are. The chamber
is about 7 feet long by 2 feet in height and
width, and its mouth is closed by a carefully
fitting lid having two holes in it. One of these
holes serves as an inlet for the air whilst the
other is the outlet. The inlet aperture has
screwed into it a long tube which reaches
nearly to the further end of the chamber.
This pipe is connected with an ordinary gas
holder filled with air fitted with a tap, as is
also the outlet pipe, which is of course very
short. The articles to be operated upon are
placed in the chamber and the cover is luted
and screwed tightly on. The temperature is
then raised to the required degree, for ordinary
purposes a dull red heat being employed.
At the end of every hour a sufficient quantity
is driven into the retort to sweep out the deoxi-
dised air, after which the inlet and outlet
cocks are again closed. After a certain time
which, as we have stated, varies with circurn--
stances, the articles are withdrawn, and are
found to have received a perfect coating of
oxide. The color of this coating is exceeding-
ly pleasing to the eye being a grey or neutral
tint of varying depth, that is to say, ranging
between a light and dark shade. Some sam-
RAILWAY '.N"OTES.
379
pies we have seen possess a very delicate color
and one which renders further ornamentation
by means of paint quite unnecessary. Not-
withstanding this delicacy of tint we are in-
formed that exposure to the influences of at-
mosphere and weather, and the application of
severe tests, have no detrimental effect upon it.
The apparatus used by Mr. Bower is at present
only experimental, that is, it is not adapted
either by size or arrangement for commercially
working the process. Having, however, de-
monstrated its practicability on a reasonably
large scale, we presume its adoption on a
working basis will soon follow. In such case
it is intended that the draught of the shaft
leading from the furnaces shall be the agency
by which the air will be drawn into the cham-
ber. Moreover, the capacity of the chambers
will vary with the size of the articles to be
coated, and they will be run into the chambers
on tracks so as to admit of their read}r removal
from, and the quick recharging of the cham-
bers.
We may mention that although Mr. Bower's
process answers particularly well for cast iron
it is not at present so well suited for wrought
iron. Mr. Bower, however, is now working
out some slight modifications, *by means of
which he expects to be able to attain equally
satisfactory results with both wrought iron and
steel. The cost of thus coating the iron is es-
timated at about £1. per ton, whether the ton
be a solid mass of that weight, or whether the
weight be made of a large number of small
articles. This estimate, however, may be al-
tered by the light of practice, but provided it
is not greatly exceeded, and provided also that
the process is as eas3r of application, and the
coating as permanent, as it appears, to be,
there is a promising future before Mr. Bower's
ingenious process.
which the government was induced to embark
some time since. The road, which is 400 miles
in length, is in operation, in spite of the fact
that no stations have been erected, and that
the permanent way has yet to be ballasted.
No less than forty rivers lie across the path of
the line, while at present only ten bridges have
been constructed, those bridges being of wood,
which the contractors will not guarantee to
stand any lengthened strain. Where there are
no bridges the passenger are conveyed across
the rivers, and they then re-embark in fresh
cars on the other side.
St. Gothard.— The proposal for a supple-
mentary grant in aid of the St. Gothard
Railway has been submitted to a popular vote
in the canton of Zurich, and has been rejected
by a large majority. It is believed that the
decided line taken in Zurich will give strength
to the growing impatience of seemingly unlim-
ited outlaj^, which is felt in other cantons, and
that not only will the cantonal grants in aid be
refused, but the national subvention that has
been proposed, will also fall to the ground. In
that case the undertaking must be suspended
for want of capital, unless ihe governments
of Germany and Italy, which are already
pledged to contribute a very large sum, under-
take to supply the whole of the deficit. We
are afraid, therefore, that the prospects of the
completion of the St. Gothard Railway — we
do not say by 1880, the date originally fixed,
but within any reasonable period — are gradu-
ally vanishing. Already large sums have been
expended, chiefly upon the construction of
the celebrated tunnel between Geschenen and
Airolo, but unless a much larger outlay be now
faced, all that has been done since 1871 will go
for nothing. — Iron.
RAILWAY NOTES,
ORENBURG AND CENTRAL ASIA. — A Berlin
correspondent announces that Russia is
making an effort to secure the early construc-
tion of the railroad from Oienburg into Cen-
tral Asia — 200 German miles. The money
required will be raised by a loan.
Victorian Railways.— At the close of 1876
Victoria had 702 miles of line open for
traffic, and there were further 259 miles in
course of construction. Up to December 31,
1876, the expenditure on the Victorian rail-
ways, inclusive of rolling stock- and plant, was
£13,710,364. the approximate average cost per
mile was £19,558, which will be reduced to
£15,440, when the new lines are finished. The
rolling stock comprised 61 passenger engines,
63 goods engines, 210 carriages, and 2,194
wagons, vans, cattle trucks, &c. For the year
July 1, 1876, to June 30, 1877, the receipts were
£1,074,497. For the previous year they were
£994,767.
AHalf-Flnished Railway. — The Chilian
Government has concluded a provisional
contract for the completion of the Chili and
Southern Railroad, one of the enterprises in
ENGINEERING STRUCTURES.
The Suez Canal. — The transit revenue of
the Suez Canal Company amounted for
; the first five months of this year to £651,817,
showing a reduction of £33,992, as compared
writh the corresponding period of 1877. This
| result was attributable to the reduction made
| in the tolls in April, 1877.
I^he New Eddystone Lighthouse. — It is
announced that the Trinity Board, after
six weeks' consideration, have decided to build
the new Eddystone Lighthouse themselves, and
not under contract. The estimate of the
i Board's engineer was £90,000. There were
i three tenders, the lowest, that of Mr. Pethick,
I of Plymouth, being £105,000.
The Western Morning News gives the follow-
! ing description of the proposed new structure:
; The first point which offered itself for consid-
| eration was obviously that of the precise site
' for the new work. Smeaton's tower, (the
J present building) was, of course, erected on
: the very site of its predecessors — the wooden,
, or mostly wooden, structure of Rudyerd,
which was completely destroyed by fire; and
j the fantastic building, also of wood, put up by
| Winstanley, as the first occupant of the rock,
and which, together with its author, was
I utterly annihilated in the great storm of the
380
VAN NOSTRAND7S ENGINEERING MAGAZINE.
26th of November, 1703, after a brief but use-
ful existence of three years.
The "House Rock," as it is called, upon
which the present tower is built, stands not
alone, but is only one and the highest of a
group of rocks and reefs, projecting their
jagged summits in the range of tide between
low and high water. These comprise the
House rock and reef, the South rock and reef,
the South-east reef, the East Rock, and a de-
tached spit, the North-east rock. The position
selected for the new tower is on the South
Reef, about 100 feet away from the existing
lighthouse, across the gut or channe], and in a
south-easterly direction. It has the advantage
of partial protection, towards the west and
south-west, by the House Rock and reef, but
the disadvantage of being considerably lower
in elevation. No portion of the site rises
above the half- tide level, and the lowest parts,
where the foundation courses of the new
structure are to be laid, lie 4 feet below the
low-water level of an ordinary spring tide;
whereas the rock whereon Winstanley, Rud-
yerd and Smeaton carried on their operations,
so far as relates to the immediate site of their
labors, was entirely above the half-tide level,
and its summit at the present landing-place is
not covered at high water of ordinary spring
tides. It will readily be understood that this
constitutes a material aggravation of the diffi-
culties and hazards, already great, of this new
and arduous enterprise. For not only is the
exposure to the action of surf and ground-swell
more than proportionately increased, but the
duration of the already too limited time within
which it is possible to carry on work "in the
dry " is most seriously shortened ; and no
inconsiderable portion of the basement must
be executed entirely under water. The reten-
tion of the old tower during the construction
of its successor is a sine qua non. The lower
level of the foundation for the new work has
also exercised an influence on the form, pro-
portions, and dimensions of Mr. J. N. Doug-
lass's design, which is not only very much
larger than that of Smeaton's, but varies
considerably therefrom. Fundamentally the
same general form is to be adopted ; and,
technically speaking, the shaft of the tower is
a concave elliptic frustrum,— realised in
Smeaton's original conception as the bole of an
oak, — but, in order to give weight and solidity
to the substructure, with corresponding power
of resistance to the violence of the waters, the
lower courses of masonry, up to and inclusive
of the twelfth, are to be perfectly cylindrical
in form up to the level of about 3 feet above
the high-water level of ordinary spring tides.
At this point there is a diminution of more
than 8 feet in diameter, forming a commodious
landing platform, whence springs the shaft
proper of the tower. The diameter assigned
to this cylindrical base is 44 feet, and that of
the tower at its springing is between 35 feet
and 36 feet, at a height of a little over 22 feet
above the foundations. The circular shaft
attains its smallest dimensions (18 feet 6 inches
diameter) at a height of about 134 feet above
the rocky bed of its foundation ; swelling out,
with a bold and graceful cavetto, to an en-
larged diameter of 23 feet maintained up to the
level of the gallery-course or lantern floor, at a
total height of 142 feet above the base of the
light-house, and 122 feet 6 inches above the
level of high water of ordinary spring tides.
The magnitude of this noble light-tower will
be at once apparent by comparison with the
similar dimensions of its existing predecessor.
Smeaton's shaft diminishes from a diameter of
34 feet at the foundation-course to 26 feet at
the level of high water ordinary spring tides;
and thence to 20 feet at the entrance door, and
15 feet at the top, the gallery-course being but
61 feet above high-water mark, and the lantern-
floor about 7 feet higher. Thus the new light
will be displayed at an elevation 55 feet greater
than that of the old one, and its range of visi-
bility and efficiency will be proportionately
extended. It would be superfluous, in regard
to an as yet unexecuted work, to describe
minutely all the proposed details of its con-
struction ; but some few of the general features
of the design may be glanced at with interest.
The structure is to be built entirely of granite,
and to be entirely solid (except a small water-
tank) up to the level of the entrance-floor, at
about 22 feet above the landing-platform ; the
access from low-water mark being by an
outside step-ladder, formed of gun-metal cleats,
recessed in the granite below the platform, and
projecting from the surface of the tower above
that level. The foundation is to be formed by
cutting away the rock in benchings or steps, for
the first four courses, all the stones which bed
on the rock being secured thereto by metal
bolts. Throughout the entire structure every
individual stone will be closely united, or
bonded in to those surrounding it, by solid
dovetail projections, fitting into corresponding
recesses; and each course of stones is similarly
to be connected with those above and below
it; so that in this manner, when set in Portland
cement, the entire mass will require almost the
homogeneity and strength of the solid granite
rocks from which its component elements were
quarried, as has been amply demonstrated by
experience. The hollow upper portion of the
tower will be similarly built, the rings being
formed of single stones running through from
the inside to the outside of the shaft. The
internal diameter, as proposed, varies from 11
feet 6 inches to 14 feet, and the thickness of
the ring from 8 feet 6 inches to 2 feet 3 inches.
This part is to be divided by arched granite
floors into nine stories, apportioned as stores,
coal, oil, crane, living, bed, and service rooms.
The door and window openings will be pro-
vided with gun metal doors, sashes, and
shutters ; and the general fittings of the tower
are proposed to be of the same first-class, solid,
and expensive character, — therein lying true
economy, from the very situation, nature, and
purpose of the lighthouse. Summing up the
total quantity of the granite in the proposed
new tower, it is approximately something less
than 69,500 cubic feet, giving to the mass a
total weight of about 5,150 tons of masonry.
The metal-work in cast, malleable and wrought
iron, in gun-metal, Muntz-metal bolts, copper,
and brass and other materials will make up a
gross total of about 50 tons more, or 5,200 tons
ORDNANCE AND NAVAL.
381
in the wliqle. This great mass will have to be
wrought, set up, and fitted together on shore,
takerTdown, loaded in vessels, transported by-
sea to the Eddystone rocks,— a distance of four-
teen miles from Plymouth— and there unloaded,
hoisted and built into position, at a mean height
of 43 feet above the level of low water of an
ordinary spring tide. The time allowed for
the completion of the work is five years,
giving an average of 1,030 tons to be erected in
each year, practically limited to the summer
season, so far, at least, as the actual work at
the rock is concerned, inasmuch as during the
winter half of the year it is impossible to carry
on operations of this kind at all ; and it may-
be added, indeed, that the work can only be
executed intermittently even during the sum-
mer months.
ORDNANCE AND NAVAL.
The Garrett Torpedo Boat.— We are, this
week, in a position to give details respect-
ing the Garrett torpedo boat, the launch of
which, at Birkenhead, on the 6th inst., was
tersely announced in last week's Iron. She is
a small but perfect specimen of the larger boat
which would be required for some of the more
difficult kinds of submarine work. It is cigar-
shaped, and runs rather abruptly to sharp
points at both ends, the total length from point
to point being 14 feet and the width across the
center 5 feet. It has been constructed of plates
of iron 3-16th of an inch in thickness, riveted
together, and weighs, inclusive of ballast,
about 5 tons. To the outside a coat of lead-
colored paint has been given, and this accom-
plishes the object aimed at in concealing almost
all outlines except those which rise above the
surface of the water. When floating at its
normal or resting level, the position of the boat
is revealed by a "conning tower," which rises
for about 2 feet from the center of the cigar
and forms a manhole, through which access is
obtained into the interior. In the sides of the
tower, which is of square shape, are round
glass windows for outlook, and two brass caps,
the uses of which will be explained hereafter.
The balance of the boat is preserved, and the
tower maintained in an upright position, by a
leaden keel nearly 2 feet bread and about 2 tons
in weight. An ordinary four-bladed screw-
propeller revolves at one end of the boat
mounted on a shaft, which communicates with
the interior through a water-proof chamber.
The steering power is obtained by means of
rudders worked by suitable gear from within.
These outward appliances and accessories,
however, add little to the apparent bulk of the
boat, most of them being almost invisible even
when the craft is resting at the surface. Little
unnecessary and unoccupied space is to be
found within, although there is ample room
for the movements of the operator. Upon the
latter falls the task of propelling the boat
through the water, and he causes the screw to
revolve by means of an ingenious combination
of treadle and fly-wheel. Of the more import-
ant features of the interior are some water-
tanks located at each end of the boat, and a
force pump, with powerful lever handle and
tap, within easy reach of the manipulator.
This is the actual machinery of descent as dis-
tinguished from that of propulsion. Once
within and assurred that the manhole cover
has been securely closed down upon him, the
operator descends to the desired depth by turn-
ing the tap to his right. This admits into the
tanks a quantity of water, which, overcoming
the buoyancy of the boat, causes it to sink
rapidly. The descending motion may be
slackened, as it may be arrested, by the same
method. But to cause the boat to ascend it
becomes necessary to use the force pump.
This appliance, by expelling the water from
the tanks, restores the lost buoyancy, and the
boat ascends with a rapidity exactly dependent
upon the amount of force employed. It ma}"
sink to a depth of 30 feet, or may linger 6 feet
below the surface, and it can be moved for-
ward or backward at any desired distance from
the surface. The details of the inventor's
method of purifying the air within the boat.
in order to make it supportable during a close
confinement of perhaps several hours, are at
present secret, and form, without doubt, a
main feature of the scheme. In his descent
the operator takes with him a number of iron
tins of compressed air, a bottle of oxygen, and
a number of tin cases containing a mixture of
chemicals. A case is strapped to his back
after the manner of a knapsack, and when seen
at work through one of the windows, he is ob-
served inhaling air, and as rapidly sending it
through a tube which enters his mouth and
passes over his head to the case on his back.
The air passes through the chemicals, is puri-
fied, and again enters the lungs of the operator,
to be again sent through the tube for purifica-
tion. When a case is exhausted of its purify-
ing properties another must be taken up and
mounted. But these are not the only duties,
apart from the mere working of his vessel,
which fall to the lot of the submarine traveler.
Oxygen must be added from time to time, and
danger is sure to ensue if he forget the import-
ant role played in the safe navigation of the
boat by the compressed air. He is careful to
maintain as far as possible a mean between the
outward pressure of the water, which increases
with the depth, and the inward pressure of the
air, which he is at pains to augment when
necessary by opening one of his cases of air.
In addition to this, he is supposed to keep a
bright lookout for all objects lying in his way,
or moving in his vicinity. If attacking a man-
of-war lying at anchor, he descends to the
necessary depth, moves cautiously forward,
and when close to the mooring or other chain
unscrews the two caps in front of his tower.
This operation gives entrance to a quantity of
water, but as the holes are merely flanked in-
ternally by a long flexible arm-sleeve of stout
material closed at the inner end, no water
actually enters the boat. Viewed from within,
these sleeves would look like long pendent
stockings hanging down inside full of water.
The operator pushes his arm through them,
turning them as it were inside out, as he pushes
them through the holes into the water around
his vessel. Using each as a sort of glove, he
attaches a hook hanging outside his boat to the
382
VAN nostrand' s engineering magazine.
chain of the man-of-war, puts on his caps, and
moves his craft quickly to the rear. The mo-
tion draws taut a loop line, and runs a torpedo
from his rear up to the chain, where it is ex-
ploded either by the shock of contact or by
electricity. The weakest part of the hull of a
large vessel might thus be sought out and at-
tacked with tremendous effect.
When the boat is below the surface artificial
light is of course necessary Mr. Garrett has
discarded all methods capable of adding im-
purity to the atmosphere. He uses a lamp
formed of two Gassiot (glass) tubes, partly ex-
hausted of air. When a current of induced
electricity is passed through these tubes a soft
bluish light is the result, and there is sufficient
illumination for all the necessary operations.
The ordinary electric-light, of much brighter
flame, would have to be employed for purposes
of exploration or observation without, and the
inventor has this extension of his scheme in
contemplation. Electric communication be-
tween the boat and, say, a steam launch far in
the rear, is provided by sending and return
wires in one strand passing through a well-
stopped hole in the tower, the telephone and an
ordinary electric call-bell being sufficient for
the purpose.
The experiments were, generally speaking, of
a very successful character. Manipulated very
cleverly by the inventor, the boat sank and rose
to the surface, moved forward above, and was
propelled below many times during the five
hours occupied by the inspection. The strange
appearance of the vessel was a matter of much
remark. When floating with its tower just
level with the surface of the water it resembled
the snout of some marine monster, an impres-
sion which was strengthened when it blew up
volumes of water after the manner of a whale.
Mr. Garrett remained below on one occasion an
hour and a-half without requiring any assist-
ance, and so well had the purification of the
air been accomplished that an improvement in
the quality of the latter was noticed on the man-
hole being removed. Subsequently the in-
ventor remained below a little over an hour,
intending to illustrate his method of attaching
the torpedo and of using his arms outside the
boat. His inability to do so illustrates the pre-
cariousness of and danger of even the new
method of submarine navigation. He had no
sooner unscrewed the caps below, admitttng
the water into the sleeves, than he discovered a
leak in one of them, through which the water
spirted, threatening momentarily to enlarge the
hole, and fill the boat. He had presence of
mind enough to seize and twist the arm, and
while stopping the leak by this means, to work
the force pump with the other hand, and thus
raise himself to the surface. During the greater
part of the time, during which tlie experiments
lasted telephonic communication was maintain-
ed between the boat and the steam launch con-
veying the party.
The present speed of the Garrett torpedo
boat is about 4 or 5 knots an hour. The speci-
men under notice, however, is designed for the
use of one man. The inventor contemplates a
boat of proportionately greater strength and
size tkat may accommodate and be worked by
three men. An improvement of the means of
propulsion is also in view, the most suitable
being gas or compressed air; this would in-
crease the speed to a maximum of at least 10
knots, while increased speed would give in-
creased command over the steering of the boat.
The vessel used on this occasion was merely an
experimental one, but quite strong enough to
bear the pressure met with at a depth of 30
feet. A larger vessel would have more liberty
in this respect, but as most of the purposes of
such boats may be accomplished within a com-
paratively few feet of the surface, the capacity
to descend to great distances is by no means
absolutely necessary. Mr. Garrett has* already
been in communication with the Admiralty on
the subject of his boat, and we understand that
he is about to report the particulars of his in-
vention to that board. He attaches primary
importance to the chemical as compared with
the mechanical part of his invention, for which
he has already taken out a provisional patent.
The new boat, with all its machinery, was
made by Messrs. Cochran and Co. , engineers
and iron founders, Birkenhead, the work of
construction occupying about two months.
BOOK NOTICES
Slide-Valve Gears. By Hugo Bilgram,
M.E. Philadelphia: Claxton, Remsen &
Haffelringer. Price $1 00. For sale by D. Van
Nostrand.
This little book presents a new graphical
method for analyzing the action of slide-valves
designed to simplify the solution of all such
problems. The illustrations are abundant,
eighty in number, and are otherwise sufficient
for the purpose.
The three parts to the work treat respective-
ly of the Slide-Valve, Link Motions and Cut-
Off Gearing.
Many students who fail in obtaining needed
instruction from more elaborate treatises will
doubtless find their wants abundantly satisfied
by this compact little work.
Manual of Introductory Chemical Prac-
tice. By Geo. C. Caldwell, S.B., Ph.D.
and Abram A. Breneman, S.B., of Cornell
University. Second Edition revised. New
York: D. Van Nostrand. Price $1.50.
This manual was originally designed as a
guide for students beginning laboratory work.
The result of two years' trial justifies a new
edition of the work, and also the expectation
that it will be acceptable to teachers who wish
to illustrate a short course in chemistry.
The plan is chiefly to illustrate the character
of chemical changes as the following extract
from the contents will show : Introductory ;
Fusion-Vaporization; Solution Crystalizatiom
Conditions affecting Reactions; Properties of
the Elements; Compounds; Combining Pro-
portions; Oxidation; Flame Reduction ; Group-
ing of Elements; Binary and Ternary Com-
pounds; Bethollet's Laws; Decomposition;
Surface Action; Quantitative Analysis.
A complete list of apparatus needed is given,
with copious illustrations. This is a book that
has been long needed by teachers of Element-
ary Chemistry.
BOOK NOTICES.
383
Railroads — Their Origin and Problems.
By Charles Francis Adams, Jr. New
York: G. P. Putnam's Sons. Price $1.25. For
sale by D. Van Nostrand.
These two essays will be widely read on both
sides of tbe Atlantic. As Railroad Commis-
sioner of Massachusetts, the writer has of late
years given annually such evidence of his abil-
ity to deal with this great problem as to gain
respectful attention to his views in many coun-
tries.
The second essay, the Eailroad Problem, as
it is presented to all countries is of the most
general interest.
The masterly character of the author's pre-
vious writings in this field is evident in this
essay.
Chemical Experimentation. By Samuel
P. Sadtler, A.M., Ph.D. Louisville:
John P. Morton & Co. Price $2 . 50. For sale
by D. Van Nostrand.
This is an excellent guide to either laboratory
or lecture-room work, and will prove service-
able for either teachers or pupils.
The series of suggested experiments includes
all the non-metals and thirty of the metals.
The illustrations are numerous and of the most
excellent character. The directions for the
preparation are exceptionally clear.
An appendix gives specific instructions about
the common manipulations of the laboratory
such as cutting and bending glass, blowing
bulbs, fitting up corks, etc., etc.
Some useful tables, comparing the different
scales, are also added.
Annual Report of the Chief Signal Of-
fice to the Secretary of War for
1877. Washington : Government Printing
Office.
The present report is in no particular behind
its predecessors. Some new features in chart-
ing observations are noticeable, and the gen-
eral excellence of the maps is in every way
gratifying.
There is an evident determination in the de-
partment to maintain the position now held —
that of first in the world in all that pertains to
observing phenomena, and freely disseminating
such knowledge as is obtained from the infor-
mation received.
Ninety -five stations make tri-daily telegraphic
reports, thirty-two make one telegraphic daily
report only, and one station only sends two re-
ports ; a total of 128 stations reporting by tele-
graph.
Some reduction of the force was made by
Act of Congress, July, 1876, which it is hoped
will be but temporary. A brief examination
of the results of the last two or three years
will lead to the conviction that true economy
lies on the side of an extension of the system
of observations under the superior management
that now directs i1 .
A Treatise on Files and Rasps. By Nichol-
son File Company, Providence.
This is a beautifully illustrated thin quarto,
treating briefly of the method of file manufac-
ture and, with great fullness, of the varieties of
files and rasps manufactured by this enterpris-
ing company.
Van Nostrand's Science Series, No. 38.
Maximum Stresses in Framed Bridges.
By Prof. Wm. Cain, A.M., C.E. New
York : D. Van Nostrand. Price 50 cts.
This number discusses the Howe, Pratt,
Triangular, Whipple, Fink, Bow String and
Schwedler Bridges, for the maximum strains
caused by two locomotives and a train of cars
— the usual loads assumed in practice. A
comparison is also made of the respective
weights of these trusses as computed from the
strains. The unit strains used in finding these
weights are obtained from a modification of
Launhardt's formula, which is based upon the
well-known Wohler's law.
The new features in this book are the ana-
lytical treatment of the subject of maximum
chord strains due to the loads assumed, the
ascertaining the most economical depth of
trusses, besides other points.
The discussion of the Schwedler bridge —
which is so earnestly recommended by its
author — will probably be of interest to engi-
neers who have not studied this system.
The treatise is complete in itself; the full
analysis for each truss being given; and it is
hoped that the compact form in which the sub-
ject matter is presented— stripped of unneces-
sary matter — may prove an agreeable feature to
engineers.
MANUAL OF THE VERTEBRATES OF THE
Northern United States. Second Edi-
tion. By David Starr Jordan, Ph.D. Chic-
ago : Jansen, McClurg & ,Co. Price $2.50.
For sale by D. Van Nostrand.
This is for the use of students of zoology to
aid in identifying the species of the vertebrates
of our own country.
The author has studied briefly and has got,
we presume, a complete manual within a con-
venient-sized volume, useful to collectors all
over the country.
rpHE Life of John Fitch. By Thompson
1 Westcott. Philadelphia: J. B. Lippin-
cott & Co. Price $1.50. For sale by D. Van
Nostrand.
A new edition of this biography of the
inventor of the steamboat is noteworthy. It is
in good style, and as it is a record of an
important era in steam engineering in this
country, it is worthy of a place in every library.
MANUAL FOR MEDICAL OFFICERS OF
Health. By Edward Smith, M. D.,
F.R.S. Second edition. London: Knight &
Co. Price $3.50. For sale by D. Van Nos-
trand.
The duty of the health officer in this country
is in general not very well defined ; the func-
tions of such an officer are, as recent experi-
ences have taught us, but illy understood.
But, as in our present condition which promises'
improvement, we have followed the lead of
older countries, it is reasonable to infer that
from 'Dr. Smith's writings much may be
gleaned which will prove valuable in the
future.
Although written for use in England, a very
considerable portion of the work will be found
valuable here.
384
VAN NOSTKAND'S ENGINEERING MAGAZINE.
TAnnee Scientieique et Industrielle.
J. Par Louis Figuiee. Paris : Libraire
Hachetti. Price $1.40. For sale by D. Van
Nostrand.
This Scientific Annual chronicles the ad-
vance during 1877 in the several departments
of Astionomy, Meteorology, Physics, Mechan-
ics, Chemistry, Building Construction, Biology,
Hygiene, Medicine and Industrial Arts.
The selection of articles and their arrange-
ment for this Annual are good. The only il-
lustrations are of the Bell Telephone.
HANDBOOK OF INSPECTORS OF NUISANCES.
By Edward Smith, M. D., F.R.S. Lon-
don: Knight & Co. Price $2.00. For sale by
D. Van Nostrand.
This work is of more use in Great Britain
than in this country, being adapted to the laws
of that country. It is to be hoped, however,
that it will serve as a guide in shaping our
laws so as to insure a better condition of sani-
tary regulation in the future.
The methods of conducting examination of
sewers and of disinfecting filthy localities are
such as may be profitably followed in any civi-
lized community.
FOOD FROM THE FAR WEST, OR AMERICAN
Agriculture. By James Macdonald.
New York : Orange, Judd & Co. Price $1 . 50.
For sale by D. Van Nostrand.
This is made up from a series of letters to
the Scotsnan, which the author was com-
missioned to write to that paper, in order to
inform its readers on the subject of the import-
ation of dead meat from the Western States.
Four chapters have been added to the above to
complete the book. One of these presents
statistics, two are devoted to American Short-
Horn Breeding, and one is on what science
says to the cattle feeder.
As a summary of the meat producing
resources of our Great West, the work is
doubtless accurate, and is certainly interesting.
Sanitary Engineering. A Guide to the
Construction of Works of Sewerage
and House Drainage. By Baldwin Latham,
F.G.S., C.E. Second Edition. London: E. &
F. N. Spon. Price $12.00. For sale by D.
Van Nostrand.
The first edition of this book was speedily
exhausted. The demand was still so great that
an American reprint was issued in parts. It
gave an impetus to Sanitary Engineering in
this country which was much needed.
The second edition is much larger than the
first, the additional matter relating chiefly to
improved methods of Sewerage.
The work still holds the first place as a com-
pendium of Sanitary Engineering practice.
Electric Lighting. A Practical Treat-
ise. By Hippolyte Fontaine. Trans-
lated by Pajet Higgs, LL.D. London: E. &
F. N. Spon. Price $3.00. For sale by D.
Van Nostrand.
This work describes chiefly the Gramme
Machine and the different forms of lighting
apparatus which have been tried in connection
with it.
The subject is one of great interest, as the
time of lighting publie squares, railroad |
stations, and public halls, by the electric light,
seems certainly at hand, and, although we
have not passed the experimental stage, the
French engineers have accomplished so large a
measure of success that we are at present con-
tent to accept the methods they recommend.
The summary of their processes is presented
by M. Fontaine.
Oeuvres Completes de Laplace. New Edi-
tion. To be completed in seven volumes
4to Paris : Gauthier-Villars. Price, per vol.
$8.00. For sale by D. Van Nostrand.
The works of Laplace still hold their high
position in the estimation of students of mathe-
matical science. To read the Mecanique Ce-
leste understandingly is to earn the respect of
mathematicians ; to omit such a labor in a
course of mathematical study is to create the
suspicion in the minds of scholars that the
claims of such student to a fair order of mathe-
matical talent are, at best, pretentious.
There seems to be now no promise of a time
when these works will be held in less esteem.
Although other processes of investigation may
supersede those of Laplace, yet the accomplish-
ments of this great astronomer are so identified
with the material progress of science, that his
name is as familiar as Newton's, and libraries in
any country are incomplete without his writings.
Institution of Civil Engineers. — Through
the kindness of Mr. James Forrest we have
received the following publications of the Ex-
cerpt Minutes of the Proceedings of the Insti-
tution of Civil Engineers :
The Centrifugal Pump, by Wm. Cawthorne
Unwin, M.I. C.E.
The Flow of Water through Level Canals,
by James Atkinson Longridge, M.I. C.E.
On the Ventilation of the Mont Cenis Tun-
nel, by William Pole, F.R.SS.
_ The Strength of Flat Plates and Segmental
Ends, by Daniel Kinnear Clark, M.I. C.E.
The Main Drainage of Paris, by Felix Tar-
get, A.I.C.E.
The Huelva Pier of the Rio Tinto Railway,
by Thomas Gibson. A. I. C.E.
Chemical and Physical Analyses of Phos-
phorus Steel, by Alexander Lyman Holley,
M.I.C.E.
Railway Appliances at the Philadelphia Ex-
hibition, by Douglas Galton, F.R.S., A.I. C.E.
MISCELLANEOUS.
F)ENSSELAER POLYTECHNIC INSTITUTE.—
\) The Alumni of this celebrated Institute,
regardful as they have ever been of sustain-
ing its fame, will be gratified to learn of the
appointment of David M. Greene, C. E., as the
Director.
Professor Greene graduated at the Institute
with the class of 1851, and subsequently occu-
pied the chair of Professor of Geodesy. He
was for a time also the Professor of Engineer-
ing in the U. S. Naval Academy.
For the past few years he has been busily en-
gaged with his professional labors. He has. worn
a high rank among American Engineers, and his
recent appointment will be especially gratifying
to his confreres of the American Society of
Engineers.
VAN NOSTRAND'S
ECLECTIC
ENGINEERING MAGAZINE.
NO. CXIX -NOVEMBER, 1878 -VOL. XIX.
ON THE PKOPOSED REMOVAL OF SMITH'S ISLAND.
By Prof. LEWIS M. HAUPT.
itead before the Engineers' Club of Philadelphia.
The commercial interests of Philadel-
phia have developed to such an extent
as to create a demand for greater wharf-
age facilities with deeper water; and
that cereals and merchandise may be de-
livered without too many handlings it is
advisable that cars should be run im-
mediately alongside the vessels to be
laden. To accomplish this it is proposed
to lay tracks on Delaware Avenue, al-
ready too narrow, amd to make provision
for the space thus occupied by extending
the Port Warden's line farther out and
thus contract the river channel now only
about 800 feet wide at the narrowest
part. Several of our largest shippers
have requested permission to extend
their wharves several hundred feet.
Were this to be allowed in a few isolated
cases it would introduce dangerous bar-
riers to navigation, and if an advance be
made all along the line it would seriously
contract the channel, unless a portion of
Smith's Island can be removed.
The project is by no means a physical
impossibility, as much larger deposits
have been successfully taken away. The
work of improving the river Neva in
Russia is one of far greater magnitude
as the following clipping from the Ledger
witnesseth :
" Following the large order from Russia
for Philadelphia locomotives comes the
Vol. XIX.— No. 5—25
information that the Russian Govern-
ment has just concluded, through Major
W. R. Bergholz, a contract with the
Morris & Cummings Dredging Company
of New York, for deepening to a uniform
depth of twenty feet the channel of the
river Neva, .between Cronstadt and St.
Petersburg. Twenty-five thousand dol-
lars were cabled to Russia last week as
earnest money. The dredging ' plant '
will cost $200,000. Most of it will be
constructed in this country, and will be
on hand ready for operation on first of
May next. The quantity of mud, etc.,
to be excavated is estimated at 15,000,-
000 cubic yards, and the work must be
completed in four years. (The contract
was obtained after sharp competition
with English operators.) "
To widen the Ship Channel of the
Delaware River 1000 feet along the
Smith's Island front, and to a depth of
18 feet, would require the removal of
only about 5,000,000 cubic yards of ma-
terial at a cost of about $1,000,000.
The same width and depth of channel
may be obtained if desired, for less than
yV the cost of dredging, by a careful ad-
justment of the regimen of the river by
auxiliary constructions such as jetties,
rip-raps, sand fences or bottom-dams.
Before these structures can be located
precisely, it will be necessary to make a
386
TAN NOSTRAND'S ENGINEERING MAGAZINE.
careful examination or survey of the
river to determine its surface and mean
velocity, the nature of its bed, its cross
section, the directions of its banks and
currents, whether straight or sinuous and
its longitudinal slope. These quantities
are evidently functions of each other, and
together constitute what is known as the
regimen of the river. So mutually de-
pendent are they that a change in any
one will affect them all.
The tendency of rivers is to maintain
a constant regimen, and this fact is the
key to the solution of many problems re-
lating to river improvements.
All fresh water flowing through allu-
vial deposits carries with it in suspension
more or less earthy matter. We find,
therefore, a continual tendency to deposit
where the velocity is least, and to scour
where it is greatest, and this mechanical
action of water is constantly pushing the
river bed downwards to the sea. It is
estimated that the " Mississippi annually
transports to the Gulf a volume of allu-
vion one mile square and 241 feet high,
weighing over 400,000,000 tons, and at
the same time it pushes over the bar at
its mouth an amount equal to -fa of that
sum," making altogether over 272,000,-
000 cubic yards. This is far beyond the
limits of our present mechanical possi-
bilities. Thus the river furnishes its own
motive power, gathering up its load as it
rolls along, and dumping it at the end of
its course, not always, it is true, just
where it is desired, unless the spot be in-
dicated by depositing some obstruction,
in which case it will not fail to notice the
sign " dirt wanted here," and continue
adding until its regimen is re-established,
when it will move on as before.
Let us assume a straight length of
river-bed of uniform cross section, a cer-
tain fixed stage of water and inclination,
direction and nature of bed, and we will
find the discharge will be constant, or the
water and its suspended earthy particles
will move on with a uniform velocity,
some being deposited, it is true, while
others are pushed along or gathered up;
but the mean velocity of the parabola
representing ihe wave front will remain
uniform. So soon, however, as the above
relations are disturbed, the effect becomes
at once manifest. Suppose, for example,
the cross section be increased ; the velocity
would be reduced, and, consequently, the
carrying and scouring capacity being
limited, deposits would be formed; or if
a bend be introduced, it would retard the
threads of the current on its side of the
stream, whilst those of the opposite side,
flowing faster, must return to fill the
vacuum which would otherwise be
created, and thus be drawn over towards
the bend to receive a new impulse from
the inner threads, and by these constant-
ly recurring differences of velocities cause
the alluvium to be precipitated.
Again, should one stream intercept an-
other of lesser volume, the mouth of the
latter would become choked up with a
bar, in consequence of the reduced ve-
locity of its currents, which will then
spread out laterally in the effort to main-
tain a constant discharge, and so form
deltas. For this reason, I do not believe
the improvement at the South West Pass
to be a permanent one. The effect will
ultimately be to elongate the bar into
the deeper water of the Gulf, but the
extension will be so gradual that the ex-
pense of maintaining an open channel
will be very slight.
On the other hand, anything tending
to reduce the cross section and so in-
crease the velocity or discharge will pro-
duce a scour, and unless the bed be of rock
or hard pan, will deepen or widen the
channel. Such contraction may be ac-
complished in two ways, either laterally
by drawing in one or both banks, or ver-
tically by filling up the bottom to a lim-
ited height.
As a consequence of the principles
just enunciated we will find in an allu-
vial bed that where the distance between
the banks is least the channel is deepest;
where greatest it is shallowest, or bars
are most numerous; where points jut out,
forming elbows, there will invariably be
a shoal on the lower convex shore, whilst
on the opposite or concave side will be
found the best channel; that at the efflux
of a lake, or broad expanse of river,
where the several currents assemble be-
fore a final shoot through the contracted
water-way, there will be deposits, and
that at the mouths of rivers emptying
into running water or beaches exposed to
the winds and waves, bars will be
formed, sometimes to such an extent as
entirely to interrupt navigation.
Indeed, on the south shore of Lake
Superior I have walked over the mouths
PROPOSED EEMOYAL OF SMITH' S ISLAND.
387
of some small streams without suspect-
ing their presence, and only discovered
them by exploring inward.
With a knowledge of these principles
it is possible to predict with almost ab-
solute certainty just where shoals may
be found by a mere inspection of the
outlines of the stream.
The tendency of an elbow to cause de-
posits is one which constantly increases,
so that the bar creeps up stream to meet
the elbow and ultimately joins itself to
it, forming a spit. This so greatly re-
duces the water-way as to cause erosions
at other points that the regimen may be
preserved and thus new channels are cut
through. Hence the fickleness of rivers
with low, earthy banks.
But to return to the application :
Smith's, or more more properly Wind-
mill, Island is represented, so far back
as we have any authentic data, consider-
ably farther down the river than at pres-
ent, and it has been gradually creeping
up stream, until now its upper end is
about opposite Chestnut Street. To cor-
roborate the above theory I have ex-
amined the oldest obtainable maps in the
Mercantile Library, Pennsylvania His-
torical Society, Philadelphia Library,
City Engineer's Office, and Franklin In-
stitute, with the following results :
The map of Thos. Holme, Surveyor
General of the Province, 1681, shows a
small island opposite Spruce Street, and
another much larger about opposite
Kaighn's Point.
In 1762 Windmill Island extended from
below Christian to below Spruce Street,
with bars all the way up to Cooper's
Point. (No name to map.)
The map of Scull & Heap, 1777, gives
about the same position for the island.
On the map of 1796 the island ex-
tends from below Shippen (now Bain-
bridge) Street to below Chestnut, with a
shallow channel across it opposite Spruce
Street; or, in other words, a shoal show-
ing above water between Spruce and
Chestnut Streets, but not yet joined to
the body of the island.
Hill's map, 1808, represents six small
islands or flats dry at low water extend-
ing from Christian to Vine.
In 1811, the island extended from be-
tween Shippen to between Market or
High Street, with bars at each end, the
upper one being attached to the island,
the lower reaching to Washington Ave.
The map of a survey by Jno. A. Pax-
ton, and drawn by Wm. Strickland, En-
gineer (1824), shows three islands extend-
ing from Catherine to Arch Streets with
shoals at either end.
Port Warden's map (1836) having no
date other than that of its presentation
to the Franklin Institute, and no name,
shows the upper end of island reaching
above Chestnut Street with isolated up-
per bar extending to Arch Street. The
lower limit is not defined. (No canal
shown.)
On the map of F. I. Roberts (1838)
the island extends from Shippen to above
Chestnut Street with a separate shoal
reaching as far as Arch Street, and a
shoal below from Washington Avenue
to above Christian. (Canal shown as cut
through.)
Map of Chas. Ellet,Jr. (1839); island
from South to between Market Street
(with canal) and isolated bars above and
below, the latter reaching from below
Washington Avenue to Fitzwater Street,
the former to Cherry Street. Total
length with bars, If miles.
The U. S. Coast Survey map (1843)
shows the island as extending from Ship-
pen to between Market, with ferry canal
cut through, also a detached bar below,
dry at low tide; one fathom depth just
above Washington Avenue, and an at-
tached bar on the up-stream end extend-
ing to Cherry Street, with one fathom of
water below Callowhill Street.
The Surveys of Richard Hexamer
(1868) limit the island by the prolonga-
tion of South and Chestnut Streets; and
Dyer's map of 1869 makes it reach from
Shippen nearly to Arch Street.
Of all these the only maps giving any
information concerning the depths are
those of the IT. S. C. S., made in 1843 —
and the Port Warden's map having no
date affixed — and, consequently, the only
one upon which any reliance can be
placed is that of 1843. Still a general
comparison of all shows an average
movement of the lower end of the island
up stream from Christian to South Street,
a distance of 1900 feet in 106 years, or
from 1762 to 1868.
From the comparative soundings of
1819 and 1836 as given on the Port
Warden's Map and those of the Coast
388
VAN NOSTRAND's ENGINEERING MAGAZINE.
Survey of 1843, we are enabled to trace
in plan the axes of the deepest water at
those dates with the following notable
results. In 1819 the axis was 250 to 300
feet from the Port Wardens line and
very nearly parallel thereto. In 1836,
after 17 years, it had evidently moved
slightly towards the City shore, and in
1843 was still nearer from Race Street to
Chestnut Street, approaching to within
90 feet of the pier heads at Market
Street. At Chestnut Street it made a
bend, convex towards Smith's Island,
having its maximum ordinate opposite
Walnut Street, and remained outside the
lines previously occupied to beyond the
limits of the maps.
Theory would suggest that as the ap-
proach to the island happened just op-
posite the canal cut for the Philadelphia
and Camden Ferry Company, it must
have resulted from the set of the current
in that direction, and as there is a corre-
sponding flexure of the deepest water
line in the Jersey channel it corroborates
the theory.
A search for the date of the opening
of the canal resulted in a note from Mr.
Thompson Wescott to the effect that
"the work was authorized by Act of
Council, Feb. 14, 1838, and damages
assessed the same year @ $2000. The
Canal, 150 feet wide, was cut soon after-
wards," he supposes in 1838-9. At first,
both sides of the canal were of the same
length, in consequence of which it filled
up rapidly, but by extending the upper
side into the Jersey channel to intercept
the flood tide and the lower side into the
Pennsylvania channel, to catch the ebb,
and cause a scour, it has since been kept
open. The survey of 1843, four years
after the opening of the canal, shows a
very marked effect upon the axes of the
currents. An examination of the profile
shows 29 feet opposite the old Navy
Yard, near the lower end of Shoal, below
the island. Thence the depth increases
with undulations to 58 feet at a point
above Race Street, at the upper end of
the shoal above the island (distance
6800 feet), whence it suddenly shoals to
31^ feet opposite Cooper's Point (distance
3200 feet),- at which place the river is
widest.
It deepens again to 37 ft. opposite lower
end of Petty's Island, and shoals gradu-
ally to a point above the Reading Com-
pany's wharves where there are but 19
feet of water, thence the depth increases
to 26 feet at head of island, and, finally,
runs up to only 13 feet, just below
Fisher's point, where it pitches down
suddenly to 38 feet.
Returning by the Jersey channel we
find the distance somewhat greater, by
the deep water line, because it is more
sinuous in consequence of the greater
width of channel and less depth of water.
The same general observations obtain in
this case as in the other, i. e.t where the
river is broadest it is shallowest and vice
versa. Considering the profiles of the
two channels together, we find, as a rule,
the average depth greatest where the
breadth is least, and the reverse, so that
we may safely conclude from these
(observations and deductions) that if
by any means the breadth or depth be
reduced the depth or breadth will be in-
creased in consequence of the scour pro-
duced by the increased velocity given to
the stream. This diminution of the
sectional area may be produced either
laterally by constructing jetties and
levees, or vertically by forming sub-
aqueous dykes or dams on the bed of the
stream, and crossing the same either di-
rectly or obliquely. The latter being
generally better as it will change the di-
rection of the resultant thread of the
current so as to cause it to act more
powerfully on the deposits to be removed.
In applying these principles to the case
in point, I should recommend the latter
method of reducing the water-way by
oblique dams (see map) constructed,
first of large stone thrown into the river
on range lines established by signals
erected on the island, and filling in on
the up-stream side with rip-rap or bal-
last from vessels. The Penna. end of
the dam should be somewhat higher than
that resting on the island, and no part
of it should have less than thirty feet of
water over it at mean low tide. As an
auxiliary structure I should extend the
pier heads near Willow Street (see map)
down stream, at such an angle as to de-
flect the current towards the head of the
island, and believe, that by thus expend-
ing a few thousand dollars, the present
channel may be so deepened and widen-
ed, as to avoid entirely the removal of
the island. At present I do not think it
advisable to remove any of the fast land
PROPOSED REMOVAL OF SMITH'S ISLAND.
389
DELAWARE RIVER /nr7^b
from Cooper's Pt.to Kaigh
Surveyed in I 843
O IOO 300 500
Can
390
VAN NOSTRAND'S ENGINEERING MAGAZINE.
which is now sufficiently protected by a
casing of piles; but, on the contrary, I
believe it would work serious injury to
the harbor were any very considerable
part of the island to be removed, as in
that case the deep water channel would
recede from the Penna. shore where bars
would soon form and destroy the ap-
proach to the harbor. It is also service-
able as a breakwater, besides furnishing
so much more room for stowage and
wharfage which are as essential to com-
mercial interests as good water.
I do not believe the time has yet ar-
rived when it will pay to pull up the
piles now surrounding the island, and
set them further back, but I do think it
would be expedient to deepen the chan-
nel close up to the present wharf lines
on the island by the inexpensive method
proposed.
The question will naturally arise as to
the effect upon the lower reaches of the
river from the alluvium thus disturbed.
It is my opinion that it will not seriously
affect the present navigable channel, but
it will doubtless add to the magnitude
of the bars already existing below Green-
wich, Gloucester and Red Bank.
As to the time required to effect these
changes it is impossible to make any pre-
dictions with certainty, for it will depend
largely upon the stages of water, and be
retarded to a considerable extent by the
flood and stand of the tide, but it will
doubtless improve the channel, at least
as rapidly as the demand for greater
shipping facilities increases.
A new survey of the river is now be-
ing made by the U. S. C. S., under the
supervision of Oapt. S. C. McCorkle, the
results of which will be looked for with
great interest, as indicating more cor-
rectly than can be done by other means
the exact location of any proposed im-
provement.
WATER SUPPLY TO A STAMP MILL IN VENEZUELA, WITH
NOTES ON KUTTER'S FORMULA.
By WM. A. BIDDLE.
From a Paper read before the Engineers' Club of Philadelphia.
In making the necessary calculations
for the location and construction of
works to supply water to a quartz mill
in the gold region of Venezuela, South
America, the wide differences between
the formulas given by well-known au-
thorities for the flow of water in pipes
and open channels became very apparent,
particularly when applied to compara-
tively small dimensions. This mill of
thirty stamps and the general plant of the
company owning it, had previously been
built close by the outcrop of the quartz
vein and almost three miles from the
nearest stream, in the disappointed ex-
pectation, on the part of the gentlemen
then managing, of getting a supply of
water by sinking to a moderate depth on
the vein.
In order to show the conditions to
which the formulas were applied, and
also as illustrating some of the peculiari-
ties met with in that country, a few
descriptive notes are given of the works
referred to.
These consisted (see Profile) of a
pumping station at the foot of a steep
hill on the Yuruari River (an affluent of
the Essequibo), delivering water 160 feet
above the pump into a line of troughs
(7x6 inches inside, made of inch boards)
laid along the hill sides on a descending
grade of .3 per 100 for a length of 4,100
feet, the line crossing two deep ravines
by inverted syphons (of boiler flues five
inches diameter outside) 694 feet and
518 feet long, bringing the water to the
second pumping station at the foot of a
range of hills extending inland, whence
the water was delivered 195 feet above
the pump into a second line of troughs
10,450 feet in length — this line crossing
another ravine by an inverted syphon 605
feet long — bringing the water into a
ravine immediately below the stamp mill,
whence a third pump run from the mill
boilers delivered it into the mill tank;
the total surface length of the line, in-
cluding the section and discharge pipes
of the pumps, being 17,300 feet, and the
"WATER SUPPLY TO A STAMP MILL IN VENEZUELA.
391
4 444
a «- a? 5
•iJ-09-1— +'fvs4
total height gained from toe river to the
mill tank being 310 feet.
The pumps at the two stations were
Worthington's Duplex, 16-inch steam
cylinders, 8 -inch plungers, and 10-inch
392
VAN NOSTRAND'S ENGINEERING MAGAZINE.
stroke, with 6-inch suction and 4-inch
discharge pipes. The boilers were of
locomotive pattern, having forty-five 3-
inch flues eight feet long, and the exhaust
of each pump was led into the smoke
stack of its boiler. Check valves were
placed in the discharge pipes close to
the pumps, and inch pipes were tapped
in just above the valves and leading to
the boilers, wThich were thus fed by the
pressure of the water column, though
having injectors for use in case of neces-
sity.
The boards for the troughs were saw-
ed at the company's sawmill, close by
the stamp mill. The durable native
woods, with one or two exceptions which
are of very rare occurrence, are extreme-
ly hard and heavy. The boards come
from the saw quite smooth, but it is al-
most impossible to drive a nail near the
edge without splitting the wood, and,
therefore, the side boards of the troughs
were bored for the nails by a machine
fitted up for the purpose in the saw mill.
The troughs varied in length from twelve
to sixteen feet, and were so stiff and
strong that no supports were needed be-
tween the joints.
The pumps, boilers and fixtures, pipes,
pipe fittings and tools, valves, bends,
bolts and nuts, nails, indeed everything
used in and on the work except the
boards, had to be shipped by sailing
vessels from New York up the Orinoco
River some 300 miles, landed by lighters,
loaded on ox-carts, and hauled 150 miles
inland to the mines. Fortunately both
pumping stations were close to the cart
roads, but many of the syphon pipes
had to reach their destination among the
hills by being packed on donkeys.
The preliminary grade line for the
troughs was run with a builder's level,
or triangle, eight feet long and made of
boards. This was really the quickest
and handiest instrument that could be
used, for almost every foot of the dis-
tance had to be cut through the dense
tangle of vines, briers and lianas which
form the undergrowth of the tropical
forests, and the amount of chopping was
thus reduced to an opening just sufficient
to drag the triangle along, while by
driving pegs and keeping " tally " both
the measurement and the grade line
were obtained in the one operation with
enough precision for preliminary work.
The final leveling, after the line had
been approximately located and cleared,
was done with a "Heller & Brightly"
small mining level, which proved a most
satisfactory instrument.
In calculating the heads to be given to
the inverted syphons for a maximum dis-
charge of thirty-five cubic feet per min-
ute, two formulas were applied, Weis-
bach's for friction head (velocity head to
be added), and Eytelwein's as given by
Trautwine for total head, and also by
Beardmore; with the following results :
Feet long. Eytelwein. Weisbach. Dif£.
1st. Syphon, 694 . 19.09 . 14.67 . 4.42
3d. " 605 . 16.71 . 12.83 . 3.88
2d. " 518 . 14.39 . 11.04 . 3.35
11.65
Those by Eytelwein being thirty per
cent, greater than those by Weisbach.
In the absence of any record of the use
of such small pipes (4.7 inches inside) as
inverted syphons, it was thought wiser to
take the larger results though involving
a greater loss of elevation by almost
twelve feet, and also to add two feet for
bends and possible obstructions in the
pipes, so that the heads actually given
for the above lengths were twenty- one
feet, nineteen feet, and sixteen and a
half feet respectively. Trautwine. re-
marks on this subject as follows :
" Recent experimenters state that the
old formulae in use, though generally
WATER SUPPLY TO A STAMP MILL IN VENEZUELA.
393
sufficiently exact for ordinary practice,
are to some extent defective. Weisbach
asserts that for velocities less than 1^
feet per second (full one mile per hour)
the heads given by the other formulae
are too small; and for higher velocities
too great. On the other hand many
measurements by competent engineers
seem to show that the old formulae give
all the accuracy required in common
practice."
The first trial of the works, and un-
fortunately the only one made before the
engineer left the country, included only
the first pumping station, 1,500 feet of
troughs and the first syphon, and was
made under circumstances wThich ren-
dered it impossible to test the perform-
ance of the syphon further than ascer-
taining that the 22 cubic feet per minute,
then estimated to be flowing through the
troughs, passed the syphon with no indi-
cation of filling the high side. The
three syphons have now been in use
nearly two years, but the only informa-
tion yet received about them states, that
when the works are furnishing more
water than the mill needs the syphons
show no sign of filling the high sides.
This proves that the formula used was
certainly safe in this case, but it is hoped
that further details will soon be received
by which to learn how much it is in ex-
cess of safety, and whether Weisbach's
formula might have been safely used,
since an unnecessary loss of twelve feet
of elevation could hardly be considered
by Mr. Trautwine as " sufficiently exact
for common practice," and sometimes
might be of very serious importance.
At the trial, during which the pump
was run slowly, the water flowed in the
troughs three inches deep, and a small
piece of inch board floated through the
1500 feet in 9^ minutes, or at the rate of
2.7 feet per second. If this was the true
surface velocity, then taking the ratio
between the surface and mean velocities
at .85, the mean velocity would have
been 2.3 feet per second, giving a dis-
charge of twenty cubic feet per minute.
But the float was of such heavy wood
that it was immersed its entire thickness,
thus having its under side only two
inches from the bottom of the trough,
and there can be no doubt that if a
strictly surface float, such as a thin disc
of light wood, had been used, a consid-
erably greater velocity would have been
shown. Moreover the line of troughs in
following the grade along the contour of
the hillsides had almost constant changes
of direction at the joints, while the
formulas for discharge through open
channels are given for straight channels,
so that in order to compare them closely
with the observed result in this case a
correction should be applied to the re-
sult both for thickness of the float and
for crookedness of the channel.
The differences between the formulas,
both older and more recent, that were
tried on this case, are in the values given
to the co-efficient C in the formula for
mean velocity, in feet per second,
v=<yss
in which R is the hydraulic mean radius
(area of water section divided by its wet
perimeter), and S is the fall in one unit
of length. Here the water section was
7X3 inches, or .58 X. 25 feet=.145; and
R = — = .134. The fall being
.25 + . 58 + . 25 &
.3 per 100,
S = .003, and a/KS^=a/.134x.003 = .02
Beardmore gives for ordinary use,
V=94.2 VRS
And for "channels constructed with
great care and straight in direction,"
V-100VKS
The former gives in this case a mean
velocity of 1.88 feet per second, and the
latter two feet, corresponding at 85 per
cent, to surface velocities of 2 2 and 2.35
feet per second respectively — both much
below the observed result even without
correction.
Weisbach gives 92.5 as the co-efficient
of /\/KS, and other authorities vary from
68 to 100.
Bazin gives four different co-efficients
for different degrees of smoothness in
the material of the channel, all including"
the hydraulic mean radius as a factor,
and the greatest being, for smooth plank
(Higham's tables),
V=
A/ „ /R + .098\
\ .0000457 (— ~ )
Vrs
This, applied to the case in question,
394
van nostrand's engineering magazine.
(■
gives a co-efficient of 112.36, and a mean
velocity of 2.25 feet per second, corre-
sponding at 85 per cent, to a surface ve-
locity of 2.64 feet per second — still below
the observed result even without correc-
tion.
Kutter's co-efficient includes as factors
both the hydraulic mean radius and the
inclination, and also a "natural con-
stant " depending on the material, and
for which a table of values is given, vary-
ing from .009 for smooth plank to .035
for rivers and canals full of weeds and
stones. The formula is thus (Higham's
tables)
1.811 .00281\ _
.41-6+-n +— KR ._
Taking the value of N for smooth
plank = .009, this gives for the case in
question a co-efficient of 119.145, and a
mean velocity of 2.383 feet per second,
corresponding at 85 per cent, to a sur-
face velocity of 2.8 feet per second,
which may be considered as agreeing
closely with the observed result of 2.7
feet per second corrected for thickness
of the float. But as this result was ob-
tained in a channel very far from straight
it would seem that even Kutter's co-effi-
cient is slightly below the truth for this
case. It is, however, very close, and
much nearer than that of Bazin, which
has been thought accurate when applied
to small channels, though acknowledged
to fail on large rivers.
According to Kutter's formula a depth
of .4 feet (say 4J inches) of water in the
troughs would have a mean velocity of
2.82 feet per second, which would give
the maximum discharge of 35 cubic feet
per minute, assumed in calculations for
the line, with a surplus velocity of 3.32
feet per second.
The English translation of Kutter's
work (by L. D. A. Jackson, A.I.C.E.)
gives an interesting account of his in-
vestigations, in which a great number of
recorded observations, as well as his own,
were tabulated and compared in various
ways and with most laborious research.
Without going fully into the mathemat-
ical details, it describes the method of
deriving the new co-efficient, which may
be said to consist largely of a synthetic
application of analytical geometry, by
plotting the observed co-efficients as or-
dinates, to abscissas representing values
of R, and to others representing values
of S.
It is claimed that this new formula
gives co-efficients of VRS which will be
found correct whether applied to a
petty drain or an immense river. The
formula of Humphreys and Abbot for
large rivers had been accepted as the
best yet proposed, but their modification
of it for small streams, when applied to
small channels with considerable inclina-
tions, is said to fail as completely as that
of Bazin on large rivers. But Kutter's
formula is said to have been proved on
the great depths and low inclinations of
the Mississippi, and to have given co-
efficients equal to those found there by
Humphreys & Abbot's observations,
which have gone as high 254.4. This
and its close agreement with observed
results in the case of the small trough
which has been described, certainly seem
to justify the claim made for it and en-
title it to the confidence of engineers,
Kutter's investigations have demon-
strated the following important and in-
teresting facts : that for a constant value
of N, when the hydraulic mean depth
(R) is one metre, the co-efficient is prac-
tically the same at all inclinations; that
with values of R greater than one meter,
the co- efficient increases as the inclina-
tion decreases, an extreme case of this
being the very high co-efficients for
the Mississippi; while with R less than
one meter, the co-efficient increases as
the inclination increases up to S— .001,
beyond which point any further increase
of inclination has practically no effect on
the coefficient, which then varies only
with R.
In the preface to the English edition
of Kutter, the translator alludes to the
anomalous fact that "the English-speak-
ing races," while taking the lead in engi-
neering progress in other directions,
have been very far behind in hydraulics,
one evidence and consequence being that
this book which appeared in Austria,
Germany, and Switzerland, in 1870, and
was immediately translated into French,
Dutch and Italian, was not published in
England until six years later, and that
too in spite of costly experience in the
irrigation works in India of the necessity
FRICTION BETWEEN A CORD AND PULLEY.
395
of more knowledge in this branch of
science. An extract is also given from
an article in Engineering, Dec. 31, 1875,
which says that Neville's tables of velo-
cities based upon Dubuat, "though ex-
pressed in hundredths of an inch, are in
reality but the wildest guesses at the
actual velocities in irrigation canals of
ordinary dimensions. Col. Cautley relied
upon Dubuat when he laid out the
Ganges Canal, and found him but a rot-
ten reed, for the water in every instance
tore along at an unexpected velocity,
and erosion of the bed and destruction
of the works followed." The writer of
this article then sets aside as unreliable
for such work almost all the familiar
text books, both original and compiled,
Continental and English, down to the
time of D'Arcy and Bazin. If engineers
in England have been behind the age on
this subject, it is to be feared that we in
America have been more so, for the Con-
tinental scientific journals of Europe (in
which Kutter's work was first published)
are less known and read here than in
England, and are hardly enough
" quoted " in our own periodicals to keep
the profession at large well posted on
the progress in those countries — else
some of our lately issued " Hand Books"
would have contained Kutter's very im-
portant results.
Kutter's Tables are in metrical meas-
ures, and are therefore not so convenient
for use here at present, as it is to be
hoped, they may be some years hence.
A smaller but more comprehensive set
of tables for open channels has been cal-
culated in English feet from both Bazin's
and Kutter's formulas, by Thomas Hig-
ham, Engineer of Irrigation Works in
the Punjab, India, which can be recom-
mended as convenient for use and re-
liable.
FRICTION BETWEEN A CORD AND PULLEY.
By I. O. BAKER.
Written for Van Nostrand's Magazine.
The method of operation, in the ex-
periments herein detailed, was to suspend
known weights to each end of a cord
passing over a fixed drum, and measuring
the friction directly by adding weights
enough to overcome the friction. The
apparatus was so arranged that the arc
of contact between the cord and drum
could be varied from 0° to 360°. This
was accomplished by arranging an arm,
which carried a pulley, so as to .revolve
about the drum. Separate observations
were made to eliminate the friction of
the pulley. In the course of the work
some difficulty was found in determining
exactly when the friction and added
weight were in equilibrium. In all cases
the mean position was the one sought.
The co-efficient was computed by the
well-known formula, given on page 617
of Rankine's "Analytical Mechanics,"
which, stated in words, is: "the ratio of
the tensions of the free ends of the cord
equals the base of the Naperian loga-
rithms raised to a power indicated by the
product of the co-efficient of friction
and the arc of contact measured in
terms of the radius."
The first series of experiments was
was made upon an oak drum 4.09 inches
in diameter, which had been turned in a
lathe and finished with medium fine
sand-paper. The cord used was a hard
twisted, three strand, cotton cord, 0.08
of an inch in diameter. The arc of con-
tact varied from 0° to 360° by steps of
10° each. All necessary corrections were
made and the co-efficient computed for
each angle. The results vary between
.2319 and .1312, the mean of the thirty-
six observations being .1599. . Up to 30°
the co-efficient diminished quite rapidly,
while from 30° to 360° it decreased
slowly as the angle increased. This is
accounted for by the fact that the cord
became harder under the increased ten-
sion. If we neglect four results, which
vary more widely from the mean (owing
probably to errors of observations) the
limits then become .1679 and .1412, and
396
YA.N NOSTKAND'S ENGINEERING MAGAZINE.
the mean .1563. The observations dis-
carded are all from small angles.
In the second series, the conditions
were the same as in the first, with the
exception of the substitution of a drum
whose diameter equals 1.81 inches. It
was noticed that in this experiment the
data agreed approximately with that of
the first series to about 140°, hence the
co-efiicient was computed only for the
twenty-one angles between 140° and
360°. The range in this case being be-
tween .1413 and .1265 and the mean
.1371. For the same angles in the first
series we would have a range from .1660
to .1412 with a mean of .1538.
The third series was made with a cast
iron drum 3.03 inches in diameter. The
surface of the drum smoothly turned
but not filed. The cord was the same as
used in the other two. Nine experi-
ments were made at angles from 20° to
360°. The mean is .1753, the maximum
.2133, and the minimum .1549.
For the fourth series the drum used in
the third series was smoothly filed and
observations made at the same angles as
before. The mean this time is .1348,
the maximum .1685, and the minimum
.1089.
[The above experiments were made
by Mr. C. G. Elliott in the Physical
Laboratory of the Illinois Industrial
University.]
THE VENTILATION OF THE MONT CENIS TUNNEL.
Bt WILLIAM POLE, F.R.SS. L. and E., M. Inst. C.E.
From Minutes of the Proceedings of the Institution of Civil Engineers.
In the discussion which took place at
the Institution in January, 1876, on Mr.
G. J. Morrison's Paper " On the ventila-
tion and Working of Railway Tunnels,"
the Author mentioned, that on a visit to
the Mont Cenis Tunnel in 1873, he saw
some large exhausters at work at the
north end, which he had reason to be-
lieve were used to effect an artificial
ventilation of the tunnel. He explained
however, that the information he obtain-
ed on that occasion was imperfect, and
that it would be desirable to procure fur-
ther data.
In the spring of 1877 he had an op-
portunity of again visiting the tunnel,
and of obtaining the further particulars
desired. The authorities of the Alta
Italia railway in Turin, who have charge
of the maintenance and working of the
tunnel, courteously gave him all neces-
sary facilities, and the engineer resident
on the spot fully explained the works.
He therefore thinks it right to make the
necessary corrections and additions to
his former statement, and so to put the
Institution in possession of the true facts
of the case.
The ventilation of the tunnel during
its construction was described to the
Institution by Mr. T. Sop with, Jr., M.
Inst. C.E., in his Paper of 1864; and in
1873 he added some further remarks
about two years after the opening. It
will be convenient therefore to take up
the subject at the point where Mr. Sop-
with left it.
No special works having reference to
the permanent ventilation of the tunnel
appear to have been included in the de-
sign. Mr. Sopwith stated there had
been an expectation that, as the Italian
end was 435 feet higher than the French
end there would be a constant natural
current established through the tunnel
from north to south. But it is difficult
to understand on what grounds such an
expectation could have been based. It
is true that the air at the southern en-
trance will, eceteris paribus, be more rare-
fied by about half an inch of mercury
than that at the northern end; but as
this rarefication is naturally due to the
altitude it can have no effect in creat-
ing a current. In a pipe 435 feet long,
placed vertically, the conditions would
be similar, but they would cause no as-
cending current, as the air within the
pipe would be in precisely the same con-
dition as the external atmosphere around
it. Hence the mere difference of level
of the two ends of the tunnel, can, per
THE VENTILATION OF THE MONT CENIS TUNNEL.
397
set have no effect in producing ventila-
tion.
This view was proved correct by ex-
perience, for, as Mr. Sopwith stated, no
such current was found to exist, and the
ventilation was often far from good.
This evil was not of sufficient magnitude
to annoy the passengers, but it was
found "bad enough to render the work
of the watchmen, rail -layers, and others
employed in the tunnel insupportable at
times."
To remedy this, advantage was taken
of the air-compressing apparatus, which
had been erected during the construction
at Bardonnecchia, by laying a pipe about
8 inches diameter through the whole
length of the tunnel, and placing cocks
upon it at intervals of 125 meters. This
pipe is still used; it is always kept sup-
plied with air compressed to about six
atmospheres, so that by opening any of
these cocks a stream of fresh air, cooled
by its expansion, is admitted at that
part of the tunnel. Whenever, therefore,
after the passage of a train, a man finds
himself enveloped in a bad atmosphere,
he opens the nearest air-cock and is at
once relieved.
The Author saw this apparatus at
work, and it appears to answer the par-
tial and local purpose intended; but it is
clear that it can do nothing worth speak-
ing of to promote general ventilation,
for the whole quantity of air supplied is
only about 450 cubic feet per minute, a
quantity much too small to produce any
effective change.
It is also found that the loud hissing
noise attending the escape of the air
from the small apertures has, on some
occasions, endangered the lives of the
men by preventing them from hearing
the approach of the trains.
At the north, or French end an ad-
ditional arrangement is adopted, namely,
the exhausting process to which the Au-
thor alluded in his former remarks.
The origin of this arrangement was as
follows: — The northern half of the tun-
nel inclines steeply upwards from its
mouth, to the center of the mountain;
and as the vitiated air generated during
the works of construction would not
naturally descend, it was necessary to
c extract it by force. For this object a
channel or culvert was formed at the
bottom of the tunnel, below formation
level, and was carried along pari passu
with the portion of the tunnel executed
from the north end. Outside the tunnel
on the hill above Modane were estab-
lished large exhausting pumps, which,
communicating with the channel, sucked,
by its means, the vitiated air from the
interior of the tunnel, the fresh air sup-
plying its place, partly from the work-
ing of the compound air machines, but
chiefly by entrance at the mouth, direct
from the external atmosphere.
After the tunnel was completed, and
when the defects of ventilation were felt,
it was resolved to retain this apparatus
in action, and it is at work still.
The exhausting apparatus consists of
four large bell-vessels, like small gas-
holders, inverted in water. These are
made to rise and fall by water-power,
and being furnished with inlet and outlet
valves, they act as air pumps, exhausting
the air from a chamber below, which is
in communication with the channel un-
der the tunnel. Each bell is 5 meters in
diameter, and works with a stroke of 2
meters, making six or eight strokes per
minute. When the Author was there
three of them were at work, at about six
strokes per minute, and he calculated
that they pumped in all nearly 25,000
cubic feet of air per minute.
The air-exhaust channel under the
tunnel is of rectangular shape, 1 square
meter in area, and it has apertures at
intervals of 500 meters, capable of being
closed and opened at pleasure. Usually
those nearest the mouth are closed, and
the more distant ones open, so as to
draw away the air as far in as possible;
but the men open any of them when they
find it necessary to clear a particular spot.
Of course the fresh air enters from the
mouth of the tunnel to supply the place
of what is removed by the exhaustion.
The Author inquired what was the prac-
tical effect of this exhausting process,
and he was told that it was insufficient
and unsatisfactory. The apertures near-
est to the mouth were found to draw
very well, but at a further distance away
little or no draught was perceived, and
consequently the process had no benefi-
cial operation where it was wanted, that
is, near the middle of the tunnel.
On examining the mechanical con-
ditions of the problem, this disappoint-
ment is easily accounted for. The quan-
398
VAN NOSTRAND7S ENGINEERING MAGAZINE.
tity of air extracted gives a velocity
along the exhaust-conduit of about 40
feet per second, and to overcome the
frictional resistance due to this, over a
length of several miles, would require
much more power than the bell-pumps
are able to afford. Their exhaustive
force is only about 20 inches of water
(100 lbs. per square foot), and they are in-
capable of doing more without exceed-
ing their hydraulic seal. Hence, under
the given conditions, the exhaustion
can only act during the first mile or two
of the tunnel, leaving all beyond un-
affected.
From the foregoing description it may
be inferred that the artificial processes
of supplying compressed air at the Ital-
ian end, and of exhausting the air at the
French end, although of some use locally
and partially, can have no important
influence in producing any thorough
ventilation of the tunnel.
In the face, however, of this inference
one is met with the undeniable fact that
somehow or other, a considerable amount
of general ventilation does go on.
There must be a large quantity of viti-
ated air produced by the frequent pass-
age of powerful engines, and yet it is
not found that the passengers are in-
commoded thereby; on the contrary,
they generally testify to the pleasant-
ness of the atmosphere in passing
through. Hence, although as before
stated, inconvenience is found by the
men immediately after the passage of
trains, it is clear that a sufficient general
movement must go on to effect, after a
time, the entire removal of the noxious
vapors. It will be interesting to inquire
how this can be explained.
The mechanical action of the moving
trains may be left out of the question; it
would have no preceptible influence in
moving the great mass of the contents
of the tunnel, and in all probability the
air only slips by them from the front to
behind as they pass along.
It has been already remarked, too,
that no current can be due to the mere
difference of level of the two ends; but it
may happen and no doubt does happen,
that, independently of this, the barome-
tric condition of the atmosphere gene-
rally may be different on the two sides of
the Alps, and a very slight difference in
this respect would suffice to create a
powerful draught. Thus, if the air pres-
sure, at the same altitude above sea-level,
differs on the two sides of the mountain
by only -^ of an inch of mercury, this
would suffice to create a current through
the tunnel of 7-J miles an hour. And
there is no doubt that, from the very
variable meteorological conditions in
these high regions, such differences,
or even much greater ones, must often
occur. A difference of J an inch of mer-
cury would generate a current of 16
miles an hour.
In addition to this there is also the
effect of the wind, as a brisk gale blow-
ing from the north or the south, as the
case may be, would have sufficient force
to give rise to some current through.
These meteorological conditions would
no doubt vary much at different periods;
sometimes they would act very power-
fully, at other times they would not act
at all. All this fully accounts for the
the statment made by Mr. Sopwith from
personal experience. He said " The dif-
ference in the rates of the air currents
was very remarkable. During a few
days he spent in the tunnel, on one day
the air was almost stagnant, and on the
following day he could hardly keep his
hat on." This is just what might be ex-
pected from currents produced by mete-
orological changes.
There is, however, another cause of
spontaneous ventilation which is always
at work, with much more regularity,
namely the heating of the air inside the
tunnel. In regard to this, the difference
of level of the two ends becomes a very
material feature; the tunnel in fact as-
sumes the function of a ventilating chim-
ney 435 feet high; and when its contents
are rarefied by heating, the production
of an ascending current from north to
south is perfectly natural. The heating
of the air may occur in two ways: it
may partly be caused by the higher tem-
perature of the walls; for although the
theories at first held as to the supposd
high temperature of the interior of the
mountain have not been borne out by ex-
perience, yet the heat is, no doubt, some-
thing greater than that outside. But
the chief source of the heat will be the
working of the engines; and it is matter
of fact, that the general temperature in-
side the tunnel is maintained at a much
higher degree than the external air at
THE DETERMINATION OF ROCKS.
399
the ends. According to Mr. Sopwith,
this temperature may be estimated at
83° to 90° Fahr., which would give an
elevation of from 30° to 60°; and calcu-
lation will show that, assuming all the
air in the tunnel to be heated to this ex-
tent, it would suffice to establish a per-
manent current from Modane to Bardon-
necchia.
The Author had, when he last came
through the tunnel, from south to north,
a practical proof of the existence of such
a current ; for although another train
had shortly before gone up from Modane,
filling the inclined part with smoke and
vapor, yet as he approached the Modane
end he found the atmosphere perfectly
sweet and clear, the whole of the foul-
ness having in the short interval been
carried away.
These three causes, then, namely the
difference in the barometer on the two
sides, the wind, and the elevation of
temperature inside the tunnel, appear in
the aggregate to be effective at present
in keeping up a fairly good spontaneous
ventilation. The traffic, however, is not
large, there being in all only twenty-two
regular trains per day passing through.
When this traffic is much increased, it
may probably be necessary to do some-
thing to improve the ventilation by arti-
ficial means.
In reasoning from this case to others,
it must be borne in mind that one of
the causes of the present spontaneous
ventilation (and probably the most ac-
tive one) depends on the inclination of
the tunnel. In such a case as that of
the St. Gothard, which is nearly level,
this cause cannot operate, and the Au-
thor is not aware what means are re-
lied on for producing ventilation. The
tunnel is a mile or two longer than that
of Mont Cenis, and of course the diffi-
culties will be proportionately increased.
THE DETERMINATION OF ROCKS— PORPHYRY.
By MELVILLE ATWOOD, F. G. S.
From "Journal of Microscopy."
The generally accepted meaning of
the term porphyry, without addition or
qualification, denotes "quartz porphyry,"
a plutonic rock, with a compact matrix
or ground mass, consisting of quartz
and feldspar, with crystals of both, hav-
ing a specific gravity of from 2.5 to 2.6,
and containing from 75 to 85 per cent,
of silica.
What rock the Comstock miners mean
when they say porphyry it would be ex-
ceedingly difficult for any one to tell.
In reading over the published reports of
the different Superintendents, they ap-
pear to be continually meeting with it at
all depths, and to the east and west of
the different bodies; also in the shape of
"horse," or dead ground, mixed with the
vein matter, and called " bird's eye por-
phyry." Now in ninety-nine cases out
of the hundred, what they call porphyry
does not in any one respect resemble
that rock, lacking by 25 per cent the re-
quired amount of silica, and having no
free quartz. A very slight examination
by any one having only a rudimentary
knowledge of geology would show that
the term porphyry, so applied, is the
most unappropriate that could be used
to describe either the west or east coun-
try rock of the Virginia portion of the
great Comstock Lode. The only way I
can account for the use of that term is
that they prefer it to saving "country
rock."
I hardly think it requires me to say
how desirable it would be, indeed, nec-
essary, for those conducting explorations
and trials on the Comstock Range, to
know and be able to distinguish the dif-
ferent rocks they meet with in their op-
erations, particularly as those rocks en-
close some of the richest mines yet dis-
covered in the world, and since the cost
of those very explorations amount annu-
ally to millions and millions of dollars.
It may be urged that the geographical
maps of the explorations of the fortieth
parallel contain most of the necessary
•information. I would recommend those
who think so to examine the maps, or
any of the cross sections of the workings
400
VAN NOSTRAND'S ENGINEERING MAGAZINE.
on the Comstock, beautifully drawn —
the work, I believe, of Mr. Stretch, but
colored by the officers of the Survey, and
they will find that the Mount Davidson
diorite is colored as syenite, and the
black dyke, a dolorite as andesite. Most
of the country rocks overlaying the
Comstock on the east are marked as
propylite and andesite. The second pro-
pylite and andesite are identical in chem-
ical and mineralogical composition, and
a slight inspection of the Sutro Tunnel
and other drainage levels will show that
petrologically they are the same, in fact,
the only difference being that the former
occurs in sheets and the latter in dykes.
When the feldspar in the so-called pro-
pylite is very much kaolinized, the rock
is sometimes termed by the miners bird's
eye porphyry. It may be said that the
new work by Ferdinand Zirkel, " Micro-
scopical Petrography," corrects most of
those errors, by admitting in the first
place that the Mount Davidson rock is a
diorite. No mention, however, or sec-
tion, is given of one of the most import-
ant rocks of the Comstock range, the
black dyke; and in the explanation of
the beautifully colored plates, he has
neglected to state the number of times
they are magnified. This is a most un-
fortunate omission, particularly so with
respect to the basaltic rocks. My atten-
tion was called to it by some remarks in
ore of the Virginia papers, wherein it
was stated that one of the handsome col-
ored plates was a section of basalt from
American Hat. Now, dolorite, aname-
site and basalt, are, in a mineralogical
point of view, the same rock, differing
only in the fineness of texture.
The following are the approximate
measurements of the crystals of feldspar
in these rocks:
In the Black Dyke, they average from
7-600 to 20-600 in length, by 1-1200 to
10-1200 in width.
In the Dolerite, they are of irregular
shape, but generally about double the
size of those in the Black Dyke; while
there are small masses containing small
needle-shaped crystals 1-300 to 4-300 in
length.
In the Basalt they average from 4-1200
to 9-1200 long, by 1-1200 to 2-1200 in
width.
Eight pages, however, in that work,
with a colored section, are devoted to
what is called " Augite Andesite." Now
though I have taken a great deal of trou-
ble, as yet I have not been able to pro-
cure a single specimen of that rock call-
ed Andesite. A few months ago, a good
authority on such matters, Alphons
Stubel, of Dresden, passed through this
city on his way home from South
America, where he had been collecting
rocks for many years. Knowing that he
had been at Chimborazo, I thought it
would be a good opportunity to get
what I wanted; so when he called upon
me I asked him as a favor to give me a
specimen of andesite. He said that he was
very sorry he could not comply with my
request, that he really did not know
any such rock.
I am fully aware that looseness in
penological nomenclature is the rule and
not the exception, and that many geolo-
gists are found writing of totally differ-
ent rocks under one and the same name.
I do not think that any distinction be-
tween rocks is worth much unless it can
be applied in the field. I have stated
that the black dyke, a dolorite, but
which from the fineness of its texture
might be called anamesite, was one of
the most important rocks in connec-
tion with the Comstock mines, from the
fact that it forms the west boundary to
all the vast treasures of the Comstock, no
ore worth mentioning ever having been
found at the west side of it ; therefore
every miner conducting operations in
that district ought to possess the neces-
sary amount of knowledge to enable him
to distinguish that rock. If you will
look at No. 12 rock and section, you will
find it is fine-grained and apparently of
so homogeneous a texture as not to ad-
mit of its constituent minerals being re-
solved by the naked eye. I have quite
a collection of specimens which have
been given to me, supposing them to be
that rock.
In 1867, when engaged in the examina-
tion of the gold mines of North Wales,
the well-known mining engineer, Mr. A.
Dean, gave me the rough tracing of the
working plans of the St. David's mine,
Clogan, near Dolgelley, and which I have
brought for your inspection. The geo-
logical features of that district are the
Cambrian rocks, overlaid by the lower
silurian. The St. David's vein is partly
in the silurian slate beds, and sheets of
THE DETERMINATION OF ROCKS.
401
greenstone (diabase) lying between the
slates, and partly in the Cambrians.
What I particularly wish to draw your
attention to, however, is the transverse
section, showing the gold-bearing and
non-gold-bearing rocks of the Clogan
mines, and the very important fact that
only those portions of the veins were rich
in gold, or productive, where the walls
were greenstone
Impressed with the truth of the dis-
covery, on my return to California I de-
voted a large portion of my time to the
examination of the enclosing and wall
rocks of the gold and silver bearing veins
of this Coast. On the formation of this
Society, I availed myself of the aid of a
microscope to carry on my investigations,
but soon found out that to do so with
anything like satisfactory result I must
get a collection of . well authenticated
foreign types, to compare with and
guide me in the work. Through the
kindness of the late Mr. David Forbes,
of London, Dr. Hector, of New Zealand,
and, in San Fransisco, of Mr. H. G. Hanks
and Mr. Charles Schneider, I have now a
collection of some 500 specimens of for-
eign types, from which, with the assist-
ance of my son, I have cut between 1,400
and 1,500 sections — some of them very
roughly done. I found it necessary to
have two or three from each specimen,
some cut very thin and others rather
thick, to show color and for examination
with the aid of a parabolic illuminator.
My collection of rock sections from this
Coast is large; but the result of it all
amounts to this; I found that every step
I took I was traveling on a road that
led me far away from what I wanted,
which was, a method to make it easy for
my fellow miners to understand and dis-
tinguish the enclosing and wall rocks of
the different lodes they were working —
these rocks having so much to do with
the productivenes of the lodes.
By the merest chance, I have found
out a simple way which I think, in a
great measure, will partly fill the gap so
much needed.
The different pieces of rock which I
now present to the Society are roughly
prepared after this method, and made so
that an inspection of the outer surface
viewed as an opaque object, with only
the aid of a common hand-magnifier,
will give all the information ordinarily
Vol. XIX.— No. 5—26
required by the miner, and. in most cases
he will find that he is able to distinguish
the structure and composition of all the
commoner rocks, so that with the help
of a small collection of foreign types,
prepared after the same fashion, he can
compare and identify those under exam-
ination. It will be necessary for them
to read up a little on the subject, and to
acquire a rudimentary knowledge of geo-
logy, which I think can be best done by
a careful study of such works as " The
Student's Manual of Geology," by J.
Beete Jukes, 1857; "Text Book of Geo-
logy," by Dana; "A System of Miner-
alogy," by Dana; "A Treatise on Lith-
ology," by Van Cotta, English Edition,
by P. H. Lawrence; and "Determination
of Rocks," by E. Jannettaz, translated
by Plympton.
The rock for examination may be pre-
pared as follows: First wash the speci-
men clean, using a brush to get rid of
any clay and dirt; then select the side or
part you wish to examine, and grind it
down on a piece of sandstone (a shoe-
maker's sharpening stone) until a per-
fectly flat surface is obtained. This will
occupy but a few minutes, unless the
rock is very hard. The surface should
then be worked down still finer with a
square emery file, using water, and after
you have obtained a sufficient polish,
wash the rock again, and then let it dry
gradually, either on a stove, or, what is
better still, a little brass table, with a
spirit lamp, the same that is used for
heating slides. When perfectly dry, heat
it again to a point, so that you can bare-
ly handle it; then polish the varnished
side while hot with a mixture of one
part of Canada balsam to three parts of
alcohol, which must be warmed before
applying it, and laid on with a camel's
hair brush. It will soon dry, and if left
for a day or two will harden, so that
you can handle it without injury.
The effect of this treatment is remark-
able, particularly on the lavas, as you
will see by the specimen of trachyte lava
from Bodie, which I now present to the
Society.
In conclusion, it is with great hesita-
tion that I have ventured to bring this
matter before you, but I do so, well know-
ing that more searching and exact meth-
ods of investigation are now demanded
by those conducting large mining opera-
402
VAN NOSTRAND7S ENGINEERING MAGAZINE.
tions, and that such terms as porphyry,
for any and all enclosing, or wall rock,
that may be met with in such mines as
the Comstock, and the term green chlor-
ides for the rich ore will not be deem-
ed a sufficient explanation, or tend to
give the mine adventurers that confi-
dence in the reports of their employees
which they should be entitled to, partic-
ularly when it is known that the rock is
not porphyry, and that the chloride of
silver is one of the accidental minerals
met with in vein matter.
I am in hopes that by thus breaking
the ice, others more capable in every
respect than myself will be induced to
communicate the results of their re-
searches on the subject.
All that can be claimed for the mode
I have suggested to you for the examina-
tion of rocks is that it is a rude and
simple way of determining some of the
commoner ones, but the application of
the microscope, even now quite in its
infancy, is, after all, what we must trust
to for exact or reliable results.
MATHEMATICAL SCIENCE.
Abstract of the Address of Mr. WM. SPOTTISWOODE to the British Association.
From "The Engineer."
Although in its technical character
mathematical science suffers the incon-
veniences, while it enjoys the dignity, of
its Olympian position, still in a less
formal garb, or in disguise, if you are
pleased so to call it, it is found present
at many an unexpected turn ; and
although some of us may never have
learnt its special language, not a few
have, all through our scientific life, and
even in almost every accurate utterance,
like Moliere's well-known character,
been talking mathematics without know-
ing it. It is, moreover, a fact not to be
overlooked, that the appearance of
isolation, so conspicuous in mathematics,
appertains in a greater or less degree to
all other sciences, and perhaps also to all
pursuits in life. In its highest flight
each soars to a distance from its fellows.
Each is pursued alone for its own sake,
and without reference to its connection
with, or its application to, any other
subject. The pioneer and the advanced
guard are of necessity separated from
the main body, and in this respect
mathematics does not materially differ
from its neighbors. And, therefore, as
the solitariness of mathematics has been
a frequent theme of discourse, it may be
not altogether unprofitable to dwell for
a short time upon the other side of the
question, and to inquire whether there
be not points of contact in method or in
subject-matter between mathematics and
the outer world which have been fre-
quently, overlooked ; whether its lines
do not in some cases run parallel to
those of other occupations and purposes
of life; and lastly, whether we may not
hope for some change in the attitude too
often assumed towards it by the repre-
sentatives of other branches of knowl-
edge and of mental activity. In his
preface to the "Principia" Newton
gives expression to some general ideas
which may well serve as the key-note for
all future utterances on the relation of
mathematics to natural, including also
therein what are commonly called arti-
ficial, phenomena. " The ancients divid-
ed mechanics into two parts, rational
and practical; and since artisans often
work inaccurately, it came to pass that
mechanics and geometry were distin-
guished in this way, that everything
accurate was referred to geometry, and
everything inaccurate to mechanics. But
the inaccuracies appertain to the artisan
and not to the art, and geometry itself
has its foundation in mechanical prac-
tice, and is in fact nothing else than that
part of universal mechanics which
accurately lays down and demonstrates
the art of measuring." He next explains
that rational mechanics is the science of
motion resulting from forces, and adds:
"The whole difficulty of philosophy
seems to me to lie in investigating the
forces of nature from the phenomena of
MATHEMATICAL SCIENCE.
403
motion, and in demonstrating that from
these forces other phenomena will ensue."
Then, after stating the problems of which
he has treated in the work itself, he says,
"I would that ail other natural pheno-
mena might similarly be deduced from
mechanical principles. For many things
move me to suspect that everything
depends upon certain forces in virtue of
which the particles of bodies, through
forces not yet understood, are either
impelled together so as to cohere in reg-
ular figures, or are repelled and recede
from one another." Newton's views,
then, are clear. He regards mathemat-
ics, not as a method independent of,
though applicable to, various subjects,
but is itself the higher side or aspect of
the subjects themselves; and it would be
little more than a translation of his
notions into other language, little more
than a paraphrase of his own words, if
we were to describe the mathematical as
one aspect of the material world itself,
apart from which all other aspects are
but incomplete sketches, and however
accurate after their own kind, are still
liable to the imperfections of the inaccu-
rate artificer. Mr. Burro wes, in his
Preface to the first volume of the
" Transactions of the Royal Irish Acade-
my," has carried out the same argument,
approaching it from the other side. " No
one science," he says, "is so little con-
nected with the rest as not to afford
many principles whose use may extend
considerably beyond the science to which
they primarily belong, and no proposi-
tion is so purely theoretical as to be
incapable of being applied to practical
purposes. There is no apparent connec-
tion between duration and the cycloidal
arch, the properties of which have
furnished us with the best method of
measuring time; and he who has made
himself master of the nature and affect-
ions of the logarithmic curve has
advanced considerably towards ascer-
taining the proportionable density of the
air at various distances from the earth.
The researches of the mathematician are
the only sure ground on which we can
reason from experiments; and how far
experimental science may assist commer-
cial interests is evinced by the success of
manufacturers in countries where the
hand of the artificer has taken its
direction from the philosopher. Every
manufacture is in reality but a chemical
process, and the machinery requisite for
carrying it on but the right application
of certain propositions in rational me-
chanics." So far your academician.
Every subject, therefore, whether in its
usual acceptation, scientific, or otherwise,
may have a mathematical aspect; as
soon, in fact, as it becomes a matter of
strict measurement, or of numerical
statement, so soon does it enter upon a
mathematical phase. This phase may,
or it may not, be a prelude to another in
which the laws of the subject -are
expreessed in algebraical formulae or
represented by geometrical figures. But
the real gist of the business does not
always lie in the mode of expression, and
the fascination of the formulae or other
mathematical paraphernalia may after
all be little more than that of a theatri-
cal transformation scene. The process
of reducing to formulae is really one of
abstraction, the results of which are not
always wholly on the side of gain; in
fact, through the process itself the
subject may lose in one respect even
more than it gains in another. But long
before such abstraction is completely
attained, and even in cases where it is
never attained at all, a subject may to
all intents and purposes become mathe-
matical. It is not so much elaborate
calculations or abstruse processes which
characterize this phase as the principles
of precision, of exactness, and of propor-
tion. But these are principles with
which no true knowledge can entirely
dispense. If it be the general scientific
spirit which at the outset moves upon
the face of the waters, and out of the
unknown depth brings forth light and
living forms, it is no less the mathemati-
cal spirit which breathes the breath of
life into what would otherwise have ever
remained mere dry bones of fact, which
re-unites the scattered limbs and re-
creates from them a new and organic
whole. And as a matter of fact, in the
words used by Professor Jellett at our
meeting at Belfast, viz., "Not only are
we applying our methods to many
sciences already recognized as belonging
to the legitimate province of mathemat-
ics, but we are learning to apply the
same instrument to sciences hitherto
wholly or partially independent of its
authority. Physical science is learning
;•
404
VAN NOSTRAND'S ENGINEERING MAGAZINE.
more and more every day to see in the
phenomena of nature modifications of
that one phenomenon — namely, motion
— which is peculiarly under the power of
mathematics." Echoes are these, far off
and faint perhaps, but still true echoes,
in answer to Newton's wish that all
these phenomena may some day " be
deduced from mechanical principles." If
turning from this aspect of the subject,
it were my purpose to enumerate how
the same tendency has evinced itself in
the arts, unconsciously it may be to the
artists themselves, I might call as wit-
nesses each one in turn with full reliance
on the testimony which they would bear.
And, having more special reference to
mathematics, I might confidently point
to the accuracy of measurement, to the
truth of curve, which, according to mod-
ern investigation, is the key to the
perfection of classic art. I might tri-
umphantly cite not only the architects of
all ages, whose art so manifestly rests
upon mathematical principles; but I
might cite also the literary as well as the
artistic remains of the great artists of
Cinquecento, both painters and sculptors,
in evidence of the geometry and the
mechanics which, having been laid at
the foundation, appear to have found
their way upwards through the super-
structure of their works. And in a less
ambitious sphere, but nearer to ourselves
in both time and place, I might point
with satisfaction to the great school of
English constructors of the eighteenth
century in the domestic arts; and remind
you that not only the engineer and the
architect, but even the cabinetmakers
devoted half the space of their books to
perspective and to the principles where-
by solid figures may be delineated on
paper, or what is now termed descriptive
geometry. Nor perhaps would the
sciences which concern themselves with
reasoning and speech, nor the kindred
art of music, nor even literature itself, if
thoroughly probed, offer fewer points of
dependence upon the science of which I
am speaking. What, in fact, is logic
but that part of universal reasoning;
grammar but that part of universal
speech; harmony and counterpoint but
that part of universal music; " which
accurately lays down," and demonstrates
— so far as demonstration is possible —
precise methods appertaining to each of
these arts ? And I might even appeal to
the common consent which speaks of the
mathematical as the pattern form of
reasoning and model of a precise style.
Taking, then, precision and exactness as
the characteristics which distinguish the
mathematical phase of a subject, we are
naturally led to expect that the approach
to such a phase will be indicated by
increasing application of the principle of
measurement, and by the importance
which is attached to numerical results.
And this very necessary condition for
progress may, I think, be fairly de-
scribed as one of the main features of
scientific advance in the present day. If
it were my purpose, by descending into
the arena of special sciences, to show
how the most varied investigations alike
tend to issue in measurement, and to
that extent to assume a mathematical
phase, I should be embarrassed by the
abundance of instances which might be
adduced. I will, therefore, confine my-
self to a passing notice of a very few,
selecting those which exemplify not only
the general tendency, but also the
special character of the measurements
now particularly required, viz., that of
minuteness, and the indirect method by
which alone we can at present hope to
approach them. An object having a
diameter of an 80,000th of an inch is per-
haps the smallest of which the micro-
scope could give any well-defined
representation; and it is improbable that
one of 120,000th of an inch could be
singly discerned with the highest powers
at our command. But the solar beams
and the electric light reveal to us the
presence of bodies far smaller than these.
And, in the absence of any means of
observing them singly, Professor Tyn-
dall has suggested a scale of these
minute objects in terms of the lengths
of luminiferous waves. To this he was
led, not by any attempt at individual
measurement, but by taking account of
them in the aggregate, and observing
the tints which they scatter laterally
when clustered in the form of actinic
clouds. The small bodies with which
experimental science has recently come
into contact are not confined to gaseous
molecules, but comprise also complete
organisms ; and the same philosopher
has made a profound study of the
momentous influence exerted by these
MATHEMATICAL SCIENCE.
405
minute organisms in the economy of life.
And if, in view of their specific effects,
whether deleterious or other, on human
life, any qualitative classification, or
quantitative estimate be ever possible, it
seems that it must be effected by some
such method as that indicated above.
Again, to enumerate a few more instan-
ces of the measurement of minute quan-
tities, there are the average distances of
molecules from one another in various
gases and at various pressures ; the
length of their free path, or range open
for their motion without coming into
collision; there are movements causing
the pressures and differences of pressure
under which Mr. Crookes' radiometers
execute their wonderful revolutions.
There are the excursions of the air while
transmitting notes of high pitch, which
through the researches of Lord Rayleigh
appear to be of a diminutiveness alto-
gether unexpected. There are the mole-
cular actions brought into play in the
remarkable experiments by Dr. Kerr,
who has succeeded, where even Faraday
failed, in effecting a visible rotation of
the plane of polarisation of light in its
passage through electrified dielectrics,
and on its reflexion at the surface of a
magnet. To take one more instance,
which must be present to the minds of
us all, there are the infinitesimal ripples
of the vibrating plate in Mr. Graham
Bell's most marvelous invention. Of
the nodes and ventral segments in the
plate of the telephone which actually
convert sound into electricity and elec-
tricity into sound, we can at present
form no conception. All that can now
be said is that the most perfect speci-
mens of Chladni's sand figures on a
vibrating plate, or of Kundt's lycopodi-
um heaps in a musical tube, or even Mr. j
Sedley Taylor's more delicate voitices in I
the films of the phoneidoscope, are
rough and sketchy compared with .these.
For notwithstanding the fact that in the
movement of the telephone plate we
have actually in our hand the solution of
that old world problem, the construction
of a speaking machine; yet the charac-
ters in which that solution is expressed
are too small for our powers of decipher-
ment. In movements such as these we
seem to lose sight of the distinction, or
perhaps we have unconsciously passed
the boundary between massive and
molecular motion. Through the phono-
graph we have not only a transformation
but a permanent and tangible record of
the mechanism of speech. But the dif-
ferences upon which articulation (apart
from loudness, pitch, and quality)
depends, appear from the experiments of
Fleemin Jenkin and of others to be of
microscopic size. The microphone affords
another instance of the unexpected value
of minute variations — in this case of
electric currents; and it is remarkable
that the gist of the instrument seems to
lie in obtaining and perfecting that
which electricians have hitherto most
scrupulously avoided, viz., loose contact.
Once more, Mr. De La Rue has brought
forward as one of the results derived
from his stupendous battery of 10,000
cells, strong evidence for supposing that
a voltaic discharge, even when apparent-
ly continuous, may still be an intermit-
tent phenomenon; but all that is known
of the period of such intermittence is,
that it must recur at exceedingly short
intervals. And in connection with this
subject, it may be added that, whatever
be the ultimate explanation of the
strange stratification which the voltaic
discharge undergoes in rarefied gases, it
is clear that the alternate disposition of
light and darkness must be dependent
on some periodic distribution in space or
sequence in time which can at present be
dealt with only in a very general way.
In the exhausted column we have a
vehicle for electricity not constant like
an ordinary conductor, but itself modi-
fied by the passage of the discharge, and
perhaps subject to laws differing materi-
ally from those which it obeys at
atmospheric pressure. It may also be
that some of the features accompanying
stratification from a magnified image of
phenomena belonging to disruptive dis-
charges in general; and that consequent-
ly, so far from expecting among the
known facts of the latter any clue to an
explanation of the former, we must hope
ultimately to find in the former an eluci-
dation of what is at present obscure in
the latter. A prudent philosopher
usually avoids hazarding any forecast of
the practical application of a purely
scientific research. But it would seem
that the configuration of these stria?
might some day prove a very delicate
means of estimating low pressures. Now,
406
VAN NOSTRAND7S ENGINEERING MAGAZINE.
it is a curious fact that almost the only
small quantities of which we have as yet
any actual measurements are the wave
lengths of light; and that all others,
excepting so far as they can be deduced
from these, await future determination.
In the meantime, when unable to ap-
proach these small quantities individu-
ally, the method to which we are obliged
to have recourse is, as indicated above,
that of averages, whereby, disregarding
the circumstances of each particular case,
we calculate the average size, the aver-
age velocity, the average direction, &c,
of a large number of instances. Bat
although this method is based upon
experience, and leads to results which
may be accepted as substantially true;
although it may be applicable to any
finite interval of time, or over any finite
area of space (that is, for all practical
purposes of life), there is no evidence to
show that it is so when the dimensions of
interval or of area are indefinitely dimin-
ished. The truth is that the simplicity
of nature which we at present grasp is
really the result of infinite complexity;
and that below the uniformity there
underlies a diversity whose depths we
have not yet probed, and whose secret
places are still beyond our reach. The
present is not an occasion for multiply-
ing illustrations, but I can hardly omit a
passing allusion to one all-important
instance of the application of the statisti-
cal method. Without its aid social life,
or the history of life and death, could
not be conceived at all, or only in the
most superficial manner. Without it we
could never attain to any clear ideas of
the condition of the poor, we could never
hope for any solid amelioration of their
condition or prospects Without its aid,
sanitary measures, and even medicine
would be powerless. Without it, the
politician and the philanthropist would
alike be wandering over a trackless
desert. It is, however, not so much from
the side of science at large as from that
of mathematics itself, that I desire to
speak. I wish from the latter point of
view to indicate connections between
mathematics and other subjects, to
prove that hers is not after all such a
far-off region, nor so undecipherable an
alphabet, and to show that even at unlike-
ly spots we may trace under-currents of
thought which having issued from a
common source fertilise alike the mathe-
matical and the non -mathematical world.
Having this in view, I propose to make
the subject of special remark some pro-
cess peculiar to modern mathematics;
and, partly with the object of incident-
ally removing some current misappre-
hensions, I have selected for examination
three methods in respect of which
mathematicians are often thought to
have exceeded all reasonable limits of
speculation, and to have adopted for
unknown purposes an unknown tongue.
And it will be my endeavor to show not
only that in these very cases our science
has not outstepped its own legitimate
range, but that even art and literature
have unconsciously employed methods
similar in principle. The three methods
in question are, first, that of imaginary
quantities; secondly, that of manifold
space; and thirdly, that of geometry not
according to Euclid. First it is objected
that, abandoning the more cautious
methods of ancient mathematicians, we
have admitted into our formulae quanti-
ties which by our own showing, and
even in our own nomenclature, are
imaginary or impossible; nay, more,
that out of them we have formed a
variety of new algebras to which there
is no counterpart whatever in reality,
but from which we claim to arrive at
possible and certain results. On this
head it is in Dublin, if anywhere, that I
may be permitted to speak. For to the
fertile imagination of the late Astrono-
mer Royal for Ireland we are indebted
for that marvellous Calculus of Quater-
nions, which is only now beginning to
be fully understood, and which has not
yet received all the applications of which
it is doubtless capable. And even al-
though this calculus be not co-extensive
with another which almost simultaneous-
ly germinated on the Continent, nor with
ideas more recently developed in
America, yet it must always hold its
position -as an original discovery, and as a
representative of one of the two great
groups of generalized algebras — viz.,
those the squares of whose units are
respectively negative, unity and zero —
the common origin of which must still
be marked on our intellectual map as an
unknown region. Well do I recollect
how in its early days we used to handle
the method as a magician's page might
MATHEMATICAL SCIENCE.
407
try to wield his master's wand, trembling
as it were between hope and fear, and
hardly knowing whether to trust our
own results until they had been submit-
ted to the present and ever-ready counsel
of Sir W. R. Hamilton himself. To fix
our ideas, consider the measurement of
a line, or the reckoning of time, or the
performance of any mathematical opera-
tion. A line may be measured in one
direction or in the opposite; time may
be reckoned forward or backward; an
operation may be performed or be
reversed, it may be done or may be
undone ; and if having once reversed
any of these processes we reverse it a
second time, we shall find that we have
come back to the original direction of
measurement or of reckoning, or to the
original kind of operation. Suppose,
however, that at some stage of a calcu-
lation our formula? indicate an alteration
in the mode of measurement such that, if
the alteration be repeated, a condition of
things, not the same as, but the reverse
of the original, will be produced. Or
suppose that, at a certain stage, our
transformations indicate that time is to
be reckoned in some manner different
from future or past, but still in a way
having definite algebraical connection
with time which is gone and time which
is to come. It is clear that in actual
experience there is no process to which
such measurements correspond. Time
has no meaning except as future or past;
and the present is but the meeting point
of the two. Or, once more, suppose
that we are gravely told that all circles
pass through the same two imaginary
points at an infinite distance, and that
every line drawn through one of these
points is perpendicular to itself. On
hearing the statement, we shall probably
whisper, with a smile or a sigh, that we
hope it is not true; but that in any case
it is a long way off, and perhaps, after
all, it does not very much signify. If,
however, as mathematicians we are not
satisfied to dismiss the question on these
terms, we ourselves must admit that we
have here reached a definite point of
issue. Our science must either give a
rational account of the dilemma, or yield
the position as no longer tenable. Special
modes of explaining this anomalous state
of things have occurred to mathema-
ticians. But, omitting details as unsuited
to the present occasion, it will, I think,
be sufficient to point out in general terms
that a solution of the difficulty is to be
found in the fact that the formula? which
give rise to these results are more com-
prehensive than the signification assigned
to them ; and when we pass out of the
condition of things first contemplated
they cannot — as it is obvious they ought
not — give us any results intelligible on
that basis. But it does not therefore by
any means follow that upon a more
enlarged basis the formula? are incapable
of interpretation; on the contrary, the
difficulty at which we have arrived indi-
cates that there must be some more
comprehensive statement of the problem
which will include cases impossible in
the more limited, but possible in the
wider view of the subject. A very
simple instance will illustrate the matter.
If from a point outside a circle we draw
a straight line to touch the curve, the
distance between the starting point and
the point of contact has certain geomet-
rical properties. If the starting point
be shifted nearer and nearer to the circle
the distance in question becomes shorter,
and ultimately vanishes. But as soon
as the point passes to the interior of the
circle the notion of a tangent and
distance to the point of contact cease to
have any meaning; and the same anoma-
lous condition of things prevail, as long
as the point remains in the interior. But
if the point be shifted still further until
it emerges on the other side, the tangent
and its properties resume their reality,
and are as intelligible as before. Now
the process whereby we have passed
from the possible to the impossible, and
again repassed to the possible (namely,
the shifting of the starting point) is a
perfectly continuous one, while the con-
ditions of the problem as stated above
have abruptly changed. If, however, we
replace the idea of a line touching by
that of a line cutting the circle, and the
distance of the point of contact by the
distances at which the line is intercepted
by the curve, it will easily be seen that
the latter includes the former as a limit-
ing case, when the cutting line is turned
about the starting point until it coincides
with the tangent itself. And further,
that the two intercepts have a perfectly
distinct and intelligible meaning whether
the point be outside or inside the area.
408
rVA]5r NOSTKAND'S ENGINEERING MAGAZINE.
The only difference is that in the first
case the intercepts are measured in the
same direction; in the latter in opposite
directions. The foregoing instance has
shown one purpose which these imagin-
aries may serve, viz., as marks indicating
a limit to a' particular condition of things,
to the application of a particular law, or
pointing out a stage where a more com-
prehensive law is required. To attain
to such a law we must, as in the instance
of the circle and tangent, reconsider our
statement of the problem; we must go
back to the principle from which we set
out, and ascertain whether it may not be
modified or enlarged. And even if in
any particular investigation, wherein
imaginaries have occurred, the most
comprehensive statement of the problem
of which we are at present capable fails
to give an actual representation of these
quantities; if they must for the present
lbe relegated to the category of imagin-
aries; it still does not follow that we
may not at some future time find a law
which will endow them with reality, nor
that in the mean time we need hesitate
to employ them, in accordance with the
great principle of continuity, for bring-
ing out correct results. If, moreover,
both in geometry and in algebra we
occasionally make use of points or of
quantities, which from our present out-
look have no real existence, which can
neither be delineated in space of which
we have experience, nor measured by
scale as we count measurement; if these
imaginaries, as they are termed, are
called up by legitimate processes of our
science; if they serve the purpose not
merely of suggesting ideas, but of actu-
ally conducting us to practical conclu-
sions; if all this be true in abstract
science, I may perhaps be allowed to
point out, in illustration of my argument,
that in art unreal forms are frequently
used for suggesting ideas, for conveying
a meaning for which no others seem to
be suitable or adequate. Are not forms
unknown to biology, situations incom-
patible with gravitation, positions which
challenge not merely the stability but
even the possibility of equilibrium — are
not these the very means to which the
artist often has recourse in order to con-
vey his meaning and to fulfill his
mission? Who that has ever revelled in
the ornamentation of the Renaissance, in
the extraordinary transitions from the
animal to the vegetable, from faunic to
floral forms, and from these again to
almost purely geometric curves, who has
not felt that these imaginaries have a
claim to recognition very similar to that
of their congeners in mathematics ? How
is it that the grotesque paintings of the
middle ages, the fantastic sculpture of
remote nations, and even the rude art of
the pre-historic past, still impress us, and
have an interest over and above their
antiquarian value; unless it be that they
are symbols which, although hard of
interpretation when taken alone, are yet
capable, from a more comprehensive
point of view, of leading us mentally to
something beyond themselves, and to
truths which, although reached through
them, have a reality scarcely to be
attributed to their outward forms?
Again, if we turn from art to letters,
truth to nature and to fact is undoubtedly
a characteristic of sterling literature;
and yet in the delineation of outward
nature itself, still more in that of feelings
and affections, of the secret parts of char-
acter and motives of conduct, it frequent-
ly happens that the writer is driven to
imagery, to an analogy, or even to a
paradox, in order to give utterance to
that of which there is no direct counter-
part in recognized speech. And yet
which of us cannot find a meaning for
these literary figures, an inward response
to imaginative poetry, to social fiction,
or even to those tales of giant and fairy-
land, written, it is supposed, only for the
nursery or schoolroom ? But in order
thus to reanimate these things with a
meaning beyond that of the mere words,
have we not to reconsider our first posi-
tion, to enlarge the ideas with which we
started; have we not to cast about for
something which is common to the idea
conveyed and to the subject actually
described, and to seek for the sympathetic
spring which underlies both; have we
not, like the mathematician, to go back
as it were to some first principles, or, as
it is pleasanter to describe it, to become
again as a little child ? Passing to the
second of the three methods, viz., that of
manifold space, it may first be remarked
that our whole experience of space is in
three dimensions, viz., of that which has
length, breadth, and thickness; and if
for certain purposes we restrict our ideas
MATHEMATICAL SCIENCE.
409
to two dimensions as in plane geometry,
or to one dimension as in the division of
a straight line, we do this only by
consciously and of deliberate purpose
setting aside, but not annhilating, the
remaining one or two dimensions. Nega-
tion, as Hegel has justly remarked,
implies that which is negatived, or as he
expresses it, affirms the opposite. It is
by abstraction from previous experience,
by a limination of its results, and not by
independent process, that we arrive at
the idea of space whose dimensions are
less than tfiree. It is doubtless on this
account that problems in plane geometry
which, although capable of solution on
their own account, become much more
intelligible, more easy of extension, if
viewed in connection with solid space,
and as special cases of corresponding
problems in solid geometry. So eminently
is this the case, that the very language
of the more general method often leads
us almost intuitively to conclusions
which, from the moje restricted point of
view, require long and laborious proof.
Such a change in the base of operations
has, in fact, been successfully made in
geometry of two dimensions, and
although we have not the same experi-
mental data for further steps, yet neither
the modes of reasoning, nor the validity
of its conclusions, are in any way affect-
ed by applying an analogous mental
process to geometry of three dimensions;
and by regarding figures in space of
three dimensions as sections of figures in
space of four, in the same way that fig-
ures in piano are sometimes considered
as sections of figures in solid space. The
addition of a fourth dimension to space
not only extends the actual properties of
geometrical figures, but it also adds new
properties which are often useful for the
purposes of transformation or of proof.
Thus it has recently been shown that in
four dimensions a closed material shell
could be turned inside out by simple
flexure, without either stretching or tear-
ing ; and that in such a space it is
impossible to tie a knot. Again, the
solution of problems in geometry is often
effected by means of algebra; and as
three measurements, or co-ordinates as
they are called, determine the position of
a point in space, so do three letters or
measurable quantities serve for the same
purpose in the language of algebra.
Now, many algebraical problems involv-
ing three unknown or variable quantities
admit of being generalized so as to give
problems involving many such quantities.
And
on the other hand, to every
algebraical problem involving unknown
quantities or variables by ones, or by
twos, or by threes, there corresponds a
problem in geometry of one or of two or
of three dimensions; so on the other it
may be said that to every algebraical
problem involving many variables there
corresponds a problem in geometry of
many dimensions. There is, however,
another aspect under which even ordin-
ary space presents to us a four- fold, or
indeed a mani-fold character. In modern
physics, space is regarded not as a
vacuum in which bodies are placed and
forces have play, but rather as a plenum
with which matter is co-extensive. And,
from a physical point of view, the prop-
erties of space are the properties of
matter, or of the medium which fills it.
Similarly from a mathematical point of
view, space may be regarded as a locus
in quo, as a plenum, filled with those
elements of geometrical magnitude which
we take as fundamental. These elements
need not always be the same. For dif-
ferent purposes different elements may
be chosen ; and upon the degree of com-
plexity of the subject of our choice will
depend the internal structure or niani-
foldness of space. Thus beginning with
the simplest case, a point may have any
singly infinite multitude of positions in a
line, which gives a one-fold system of
points in a line. The line may revolve
in a plane about any one of its points,
giving a two-fold system of points in a
plane; and the plane may revolve
about any one of the lines, giving a
three-fold system of points in space.
Suppose, however, that we take a
straight line as our element, and con-
ceive space as filled with such lines.
This will be the case if we take two
planes, e.g., two parallel planes, and join
every point in one with every point in
the other. Now the points in a plane
form a two-fold system, and it therefore
follows that the system of lines is four-
fold; in other words, space regarded as
a plenum of lines is four- fold. The same
result follows from the consideration
that the lines in a plane, and the planes
through a point are each two-fold.
410
VAN NOSTRANITS ENGINEERING MAGAZINE.
Again, if we take a sphere as our ele-
ment we can through any point as a
center draw a singly infinite number of
spheres, but the number of such centers
is triply infinite; hence space as a plenum
of spheres is four-fold. And, generally,
space as a plenum of surfaces has a
manifoldness equal to the number of
constants required to determine the sur-
face. Although it would be beyond our
present purpose to attempt to pursue the
subject further, it should not pass
unnoticed that the identity in the four-
fold character of space, as derived on the
one hand from a system of straight lines,
and on the other from a system of spheres,
is intimately connected with the princi-
ples established by Sophus Lie in his
researches on the correlation of these
figures. If we take a circle as our
element we can around any point in a
plane as a center draw a singly infinite
system of circles; but the number of such
centers in a plane is doubly infinite;
hence the circles in a plane form a three-
fold system, and as the planes in space
form a three-fold system, it follows that
space as a plenum of circles is six-fold.
Again, if we take a circle as our element,
we may regard it as a section either of a
sphere, or of a right cone — given except
in position — by a plane perpendicular to
the axis. In the former case the position
of the center is three-fold; the directions
of the plane, like that of a pencil of lines
perpendicular thereto, two-fold; and the
radius of the spheje one-fold; six-fold in
all. In the latter case, the position of
the vertex is three-fold; the direction of
the axis two-fold; and the distance of
the plane of section one-fold; six-fold in
all, as before. Hence space as a plenum
of circles is six-fold. Similarly, if we
take a conic as our element we may
regard it as a section of a right cone — :
given except in position — by a plane. If
the nature of the conic be defined, the
plane of section will be inclined at a
fixed angle to the axis; otherwise it will
be free to take any inclination whatever.
This being so, the position of the vertex
will be three-fold; the direction of the
axis two-fold; the distance of the plane
of section from the vertex one fold; and
the direction of that plane one-fold if the
conic be defined, two-fold if it be not
defined. Hence, space as a plenum of
definite conies will be seven-fold, as a
plenum of conies in general eight-fold.
And so on for curves of higher degrees.
This is, in fact, the whole story and
mystery of manifold space. It is not
seriously regarded as a reality in the
same sense as ordinary space; it is a
mode of representation, or a method
which, having served its purpose, vanish
es from the scene. Like a rainbow, if
we try to grasp it, it eludes our very
touch; but like a rainbow, it arises out
of real conditions of known and tangible
quantities, and if rightly apprehended it
is a true and valuable expression of
natural laws, and serves a definite pur-
pose in the science of which it forms a
part.
The third method proposed for special
remark is that which has been termed
Non-Euclidean Geometry; and the train
of reasoning which has led to it may be
described in general terms as follows:
some of the properties of space which on
account of their simplicity, theoretical as
well as practical, have, in constructing
the ordinary system of geometry, been
considered as fundamental, are now seen
to be particular cases of more general
properties. Thus a plane surface, and a
straight line, may be regarded as special
instances of surfaces and lines whose
curvature is everywhere uniform or con-
stant. And it is perhaps not difficult to
see that, when the special notions of
flatness and straightness are abandoned,
many properties of geometrical figures
which we are in the habit of regarding
as fundamental will undergo profound
modification. Thus a plane may be
considered as a special case of the sphere,
viz., the limit to which a sphere ap-
proaches when its radius is increased
without limit. But even this considera-
tion trenches upon an elementary propo-
sition relating to one of the simplest of
geometrical figures. In plane triangles
the interior angles are together equal to
two right angles; but in triangles traced
on the surface of a sphere this propo-
sition does not hold good. To this, other
instances might be added.
It has often been asked whether
modern research in the field of pure
mathematics has not so completely out-
stripped its physical applications as to
be practically useless; whether the
analyst and the geometer might not now,
and for a long time to come, fairly say,
MATHEMATICAL SCIENCE.
411
" Hie artem remumque repono" and turn
his attention to mechanics and to physics.
That the pure has outstripped the ap-
plied is largely true; but that the former
is on that account useless is far from
true. Its utility often crops up at unex-
pected points; witness the aids to classi-
fication of physical quantities, furnished
by the ideas — of Scalar and Vector —
involved in the calculus of Quaternions;
or the advantages which have accrued to
physical astronomy from Lagrange's
equations, and from Hamilton's principle
of varying action; on the value of com-
plex quantities, and the properties of
general integrals, and of general theor-
ems on integration for the theories of
electricity and magnetism. The utility
of such researches can in no case be
discounted, or even imagined before-
hand; who, for instance, would have
supposed that the calculus of forms or
the theory of substitutions would have
thrown much light upon ordinary equa-
tions; or that abelian functions and
hyperelliptic transcendents would have
told us anything about the properties of
curves; or that the calculus of operations
would have helped us in any way towards
the figure of the earth ? But upon such
technical points I must not dwell. If,
however, as I hope, it has been sufficient-
ly shown that any of these more extend-
ed ideas enable us to combine together,
and to deal with as one, properties and
processes which from the ordinary point
of view present marked distinctions, then
they will have justified their own exist-
ence; an4 in using them we shall not
have been walking in a vain shadow, nor
disquieting our brains in vain. These
extensions of mathematical ideas would,
however, be overwhelming, if they were
not compensated by some simplifications
in the processes actually employed. Of
these aids to calculation I will mention
only two, viz., symmetry of form, and
mechanical appliances; or, say, mathe-
matics as a fine art, and mathematics as a
handicraft. And first, as to symmetry
of form. There are many passages of
algebra in which long proce*sses of calcu-
lation at the outset seem unavoidable.
Results are often obtained in the first
instance through a tangled maze of
formulas, where at best we can just make
sure of our progress step by step, with-
out any general survey of the path which
we have traversed, and still less of that
which we have to pursue. But almost
within our own generation a new method
has been devised to clear this entangle-
ment. More correctly speaking, the
method is not new, for it is inherent in
the processes of algebra itself, and
instances of it, unnoticed perhaps or
disregarded, are to be found cropping up
throughout nearly all mathematical
treatises. By Lagrange, and to some
extent also by Gauss, among the older
writers, the method of which I am
speaking was recognized as a principle;
but beside these, perhaps, no others can
be named until a period within our own
recollection. The method consists in
symmetry of expression. In algebraical
formulas combinations of the quantities
entering therein occur and recur; and
by a suitable choice of these quantities
the various combinations may be ren-
dered symmetrical, and reduced to a few
well-known types. This having been
done, and one such combination having
been calculated, the remainder, together
with many of their results, can often* be
written down at once, without further
calculations, by simple permutations of
the letters. Symmetrical expressions,
moreover, save as much time and trouble
in reading as in writing. Instead of
wading laboriously through a series of
expressions which, although successively
dependent, bear no outward resemblance
to one another, we may read off symmet-
rical formulas, of almost any length, at a
glance. A page of such formulas becomes
a picture; known forms are seen in
definite groupings; their relative po-
sitions, or perspective as it may be called,
their very light and shadow, convey
their meaning almost as much through
the artistic faculty as through any
conscious ratiocinative process. Few
principles have been more suggestive of
extended ideas or of new views and
relations than that of which I am now
speaking. In order to pass from
questions concerning plane figures to
those which appertain to space, from
conditions having few degrees of free-
dom to others which have many — in a
word, from more restricted to less
restricted problems — we have in many
cases merely to add lines and columns to
our array of letters or symbols already
formed, and then read off pictorially the
412
van nostrand's engineering magazine.
extended theorems. Next as to mechan-
ical appliances. Mr. Babbage, when
speaking of the difficulty of insuring
accuracy in the long numerical calcula-
tions of theoretical astronomy, remarked,
that the science which in itself is the
most accurate and certain of all, had
through those difficulties become inaccu-
rate and uncertain in some of its results.
And it was doubtless some such consider-
ation as this, coupled with his dislike of
employing skilled labor where unskilled
would suffice, which led him to the
invention of his calculating machines.
The idea of substituting mechanical for
intellectual power has not lain dormant;
for beside the arithmetical machines
whose name is legion — from Napier's
Bones, Earl Stanhope's calculator, to
Schultz and Thomas's machines now in
actual use — an invention has lately been
designed for even a more difficult task.
Prof. James Thomson has in fact recent-
ly constructed a machine which, by
means of the mere friction of a disc, a
cylinder, and a ball, is capable of effect-
ing a variety of the complicated calcula-
tions which occur in the highest
application of mathematics to physical
problems. By its aid it seems that an
unskilled laborer may, in a given time,
perform the work of ten skilled arithme-
ticians. The machine is applicable alike
to the calculation of tidal, of magnetic,
of meteorological, and perhaps also of
all other periodic phenomena. It will
solve differential equations of the second
and perhaps of even higher orders. And
through the same invention the problem
of finding the free motions of any num-
ber of mutually attracting particles,
unrestricted by any of the approximate
suppositions required in the treatment of
the lunar and planetary theories, is
reduced to the simple process of turning
a handle.
Coterminous with space and coeval
with time is the kingdom of mathemat-
ics ; within this range her dominion is
surpreme ; otherwise than according to
her order nothing can exist ; in contra-
diction to her laws nothing takes place.
On her mysterious scroll is to be found
written for those who can read it that
which has been, that which is, and that
which is to come. Everything material
which is the subject of knowledge has
number, order, or position; and these are
her first outlines for a sketch of the uni-
verse. If our more feeble hands cannot
follow out the details, still her part has
been drawn with an unerring pen, and
her work cannot be gainsayed. So wide
is the range of mathematical science, so
indefinitely may it extend beyond our
actual powers of manipulation, that at
some moments we are inclined to fall
down with even more than reverence
before her majestic presence. But so
strictly limited are her promises and
powers, about so much that we might
wish to know does she offer no informa-
tion whatever, that at other moments we
are fain to call her results but a vain
thing, and to reject them as a stone
when we had asked for bread. If one
aspect of the subject encourages our
hopes, so does the other tend to chasten
our desires; and he is perhaps the wisest
and, in the long run, the happiest among
his fellows who has learnt not only this
science, but also the larger lesson which
it indirectly teaches, namely, to temper
our aspirations to that which is possible,
to moderate our desires to that which is
attainable, to restrict our hopes to that
of which accomplishment, if not immedi-
ately practicable, is at least distinctly
within the range of conception. That
which at present is beyond our ken may,
at some period and in some manner as
yet unknown to us fall within our grasp;
but our science teaches us, while ever
yearning with Goethe for " Light, more
light," to concentrate our attention upon
that of which our powers are capable,
and contentedly to leave for future
experience the solution of problems to
which we can at present say neither yea
nor nay. It is within the region thus
indicated that knowledge in the true
sense of the word is to be sought. Other
modes of influence there are in society
and in individual life, other forms of
energy besides that of intellect. There
is the potential energy of sympathy, the
actual energy of work; there are the
vicissitudes of life, the diversity of cir-
cumstance, health and disease, and all
the perplexing issues, whether for good
or for evil, of impulse and of passion.
But although the book of life cannot at
present be read by the light of science
alone, nor the wayfarers be satisfied by
the few loaves of knowledge now in our
hands; yet it would be difficult to over-
THE MAGNETIC NEEDLE.
413
state the almost miraculous increase
which may be produced by a liberal
distribution of what we already have,
and by a restriction of our cravings
within the limits of possibility. In pro-
portion as method is better than impulse,
deliberate purpose than erratic action,
the clear glow of sunshine than irregular
reflection, and definite utterances than an
uncertain sound; in proportion as knowl-
edge is better than surmise, proof than
opinion; in that proportion will the
mathematician value a discrimination
between the certain and the uncertain,
and a just estimate of the issues which
depend upon one motive power or the
other. While on the one hand he accords
to his neighbors full liberty to regard the
unknown in whatever way they are led
by the noblest powers that they possess;
so on the other he claims an equal right
to draw a clear line of demarcation
between that which is a matter of
knowledge, and that which is at all
events something else, and to treat the
one category as fairly claiming our
assent, the other as open to further evi-
dence.
And yet, when he sees around him
those whose aspirations are so fair,
whose impulses so strong, whose recept-
ive faculties so sensitive, as to give
objective reality to what is often but a
reflex from themselves, or a projected
image of their own experience, he will
be willing to admit that there are influ-
ences which he cannot as yet either
fathom or measure, but whose operation
I he must recognize among the facts of
i our existence.
THE MAGNETIC NEEDLE— THE CAUSE OF ITS SECULAR
VARIATIONS.
By THOMAS JOB, Utah.
VAKIATION IN THE DECLINATION.
Nearly three centuries ago philoso-
phers observed that the magnetic needle
did not always lie in the same direct line,
even on the same meridian, but that in
the northern hemisphere its north pole
has a secular movement around a certain
point or pole, not far from the pole of
the world; it points sometimes to the
east and at other times to the west of
the same meridian, performing the north-
ern half of a revolution in 318 years.
" The Earth a Great Magnet " (Prof. A.
M. Mayer.) A very remarkable phe-
nomenon is observed — it follows the law
of a swinging pendulum — retarding in
velocity from the meridian of the sta-
tion to its easterly or westerly tropic.
In the year 1622 the declination of the
needle at London was 6° to the east of
the geographical meridian. In 1660 the
needle pointed due north and south, thus
varying 6° in 38 years, while vibrating
near the meridian of the place. In 1818
the needle varied, according to Prof.
Watts, 24° 36' to the west, and in 1865,
21° 6' west; that is, varying only 3° 35'
in 45 years, when moving near its west-
erly tropic.
The cause of this secular change in the
declination of the compass needle has
been a theme of investigation with
philosophers ever since its discovery,
and in no time more ardently than
in our day; but no satisfaction has
yet been given to scientists. All that
has been accomplished by observers is to
show that the north magnetic pole is
now vibrating from west to east, and at
| London, approaching the meridian.
It has been further observed that the
magnetic needle, in its grand secular
swing, makes some minor vibrations and
| deflections, some of which appear to
follow regular laws and be periodical;
their physical cause is found to be
dependent on the sun as primary mover;
others are evidently irregular changes,
disturbing more or less the periodical
variations.
The most remarkable of the periodical
variations is what is called the daily
vibration ; it manifests its relation to the
sun by following him in his apparent
daily motion around the earth, in the
northern hemisphere, and during the
hours of the day from east to west, and
from west to east in the hours of the
414
VAN nostrand's engineering magazine.
night; but the contrary way in the
southern hemisphere.
These easterly and westerly variations
in all parts of the globe where observa-
tions have been made, are obviously
governed by distinct laws. The west-
erly deflections in the British Isles, as
represented by the self-moving records
at Kew, as Dr. Noades observes, have
their chief prevalence from 5 a. m. to 5
p. m., and the easterly deflections during
the remaining hours, causing the needle
to return to its former position by 5
o'clock the next morning.
The extent of the daily oscillation of
the needle is small, and also variable.
Its mean value at Philadelphia, as
observed by Dr. Bache, is 7.5'. The
mean extent of the vibration at any
station varies with the daily changes in
the sun's declination, and so having
semi-annual inequality, being deflected
towards the east, and therefore with a
negative sign, or less than unity, when
the sun is north of the equator; but
toward the west, and consequently more
than the mean, when the sun is south of
the equator.
The annual variation, independent of
the daily, is a very small quantity,
amounting, in the British Isles, to only
about 59.56 sec, as given by General
Sabine, being 28.95 sec, from March
21st to the 21st of September, with the
signs minus and plus 29.9 sec, during the
remaining six months. It affects in like
manner both the northern and southern
needles.
The daily variation of the needle also
varies with variation in the latitude of
the observer; reckoning from a certain,
and seemingly fixed line, termed the
magnetic equator. In fact the needle, in
its daily swing, does not play backward
and forward, pendulum-like, across the
meridian of a station, but virtually its
north pole revolves with the sun around
the earth — toward the west in the north-
men's day, and toward the east in the
day of the southern hemisphere. So in
the southern hemisphere the motion of
the needle appears to be reversed,
towards the east in the day time and
towards the west in the night.
The case is also the same with the
secular vibration; in the southern hemi-
sphere the needle appears to vibrate in
the opposite direction to what it does in
the northern.
Only that part of the daily motion in
which the needle swings westward
belongs to the northern hemisphere; the
same with its corresponding secular
vibration; and that part below the earth,
where the needle moves from west to
east, represents the secular swing in the
southern hemisphere; even as it is day
there when it is night with us, and the
positive pole of the needle follows the
sun.
Proper investigation will show that
this daily vibration is the fundamental
cause of both the annular and the secular
variations of the magnetic needle.
There are in our common year 366
siderial days, but only about 365^ solar
days, that is, while the earth rotates 366
times on its axis it revolves once in an
orbit around the sun in the same direc-
tion,— from west to east, — and thus we
have only 365^ days out of 366 earth
rotations; so the sun appears as if to
step backwards — toward the west — from
the earth, to the amount of one day's
motion in a year. Thus he continues to
recede westward from the earth — in the
northern hemisphere, by the same space,
year after year, till he returns again to
the starting point in the orbit, where the
earth will meet him, after gaining on
him one whole revolution. The pole of
the magnetic needle, which, as shown
above, respects the sun in all its move-
ments, also recedes westwards — in the
northern hemisphere — from the meridian
of the place by the space of one day's
westward swing in a solar year. From
this point of view, one can clearly dis-
cern, that our theory admit, that the
magnetic equator of a planet lies direct
in the plane of the equator of the sun,
hence, in the case of our earth, it inclines
to the ecliptic, according to Dr. Herschel,
by the angle of 7° 207. But the axis of
the ecliptic inclines to that of the earth's
equator by the angle of 23° 27' nearly,
from which take the angle 7° 20', and
there remains 16° 7' for the inclination
of the earth's equator to that of the sun,
which is the very degree given by Dr.
Mayer as the mean inclination of the
magnetic equator to the terrestrial, as
found on actual observations.
Now, it is evident that that magnetic
meridian which passes through the node,
THE MAGNETIC NEEDLE.
415
or point of intersection of these two
equators, is at right angles with the
magnetic equator, and consequently
inclines to the true meridian at that
point by the same angle of 16° 7'.
When the needle in its secular swing
comes to this meridian — which I shall
term the prime — the rate per year of
declination should be of the greatest
value, and its tropics, east and west,
should decline from it by the same angle
of 16° nearly.
Next I shall inquire, as to whether
this accords with the observations
already made by scientists. The follow-
ing table gives the declination of the
compass needle at London, with the
mean rate of its motion as referred to I
periods of observation between 1580 to |
1865, comprising a part of an easterly,
half, the whole of the westerly, and a
part of the next westerly half vibration. I
(Sir Wm. S. Harris' Rudiments of Mag-
netism. Dr. Woad's Ed. page 258; also
Dr. Lloyd of Dublin).
EASTERLY DECLINATION.
Years of observation 1580 1622 1660
Declination 11°5' 6°0' 0=0'
Rate per Year of Declinat. 0°7' 0°8' 0°10
WESTERLY DECLINATION.
Years. 1692 1723 1730 1765 1818 1852 1865"
Decl. . 6°0' 8°36' 13°0' 20°0' 24°36/ 22=30' 20°44'
Rate p. Y. 11' 11. V 11.5' 0.9' 0.0' 0.5' 0.7'
Here we see that the rate per year of
the variation was greatest about 1723,
the time the declination at London was
8° 36', that the tropic was reached in
1818 when the rate per year was zero,
and the declination from London 24° 36'
or about 16° from the point where the
rate per year was the greatest, or the
node of the two equators.
Now, this prime meridian, or that
which lies in the plane of the sun's axis,
and intersects the two equators at their
nodes, must become an important line in
terrestrial magnetism, for when the
horizontal magnet, on its secular swing,
passes over it, it is then at its greatest
amplitude, or most distant point from
its tropics, its rate per year the swiftest,
and the daily vibration of the greatest
value; and the nearer a station is to this
line on the same magnetic latitude, the
greatest in proportion is the visible
range of its daily vibration.
And even this is not all. When the
dipping needle, in its secular vibration,
comes to this line, it is always in one of
its tropics. This is, as I shall soon prove,
the very line of its apsides.
I have now arrived at my evidence
that the magnetic equator of the earth
lies in the plane of the equator of the
sun, and since the magnetic pole revolves
about that of the earth, it is plain, that
the magnetic meridian cannot, in all
places, and at all times cut the magnetic
equator at right angles; it can only do
so at that place called the nodes of the
two equators.
Sir Wm. Snow Harris, in the volume
just alluded to, observes that the oscilla-
tion of the needle across the true meri-
dian is variable, that the limit of its
angular variation at London is 24° 36'.
it seems that he also understood, that
the limit is not of that amount at all
places, that it is only so at London, and
those places under the same meridian. In
fact, this angular variation at any station
depends on the distance of its meridian
from the prime meridian — the difference
of its declination at London from the
prime meridian is 8° 36', which added to
16° gives 24° 36', the observed angular
variation of the needle at London, when
it arrives at its westerly station where
] the variation rate per year is zero.
I further discovered, that the extent of
J the mean yearly vibration at any station
| is equal to the daily vibration at the time
! the needle comes to the prime meridian.
| The rate of the vibration at any station,
evidently increases or decreases with the
rate per year at which the needle moves
in that declination, which is as the square
root of the declination itself; both the
rate per year, and the extent of the
swing is evidently greater in the plane
of the prime meridian, even as the mag-
netic intensity is greater in the plane of
j the solar axis.
From what has been said, it is evident
that the magnetic axis only advances in
its orbit during the time the needle
j vibrates westward ; for though the earth
continues to move regularly in its orbh%
yet, while the needle moves to the east
the magnetic axis does not advance on
the earth's surface, for it only advances
westwards, as before shown, and as the
needle, which is always coincident with
the axis of the sun, only moves westward
for about half of the time, the magnetic
416
VAN NOSTRAND'S ENGINEERING MAGAZINE.
axis, in the mean, only advances west-
ward about 30' per day, as the earth
advances nearly a degree a day in the
zodiac. So, all other causes eliminated,
the whole daily advance of the needle
would only amount to that arc. But
there are other phenomena that should
be taken into consideration. The decli-
nation of the needle, as said before,
changes with the sun's declination, and
also with the motion of the earth in its
orbit. Dr. Bache in his " Magnetic Dis-
cussions," page 10, has this remarkable
expression : "The annular vibration
depends on the earth's position in its
orbit. The diurnal variation being sub-
ject to an inequality depending on the
sun's declination. The diurnal range is
greater when the sun has north declina-
tion, and smaller when south declination ;
the phenomenon passing from one state
to the other, about the time of the equi-
noxes." Also, the diurnal range appar-
ently increases as the needle in its
secular variation approaches the prime
meridian. Mr. Graham, the discoverer of
the diurnal variation, who, happily made
this discovery in 1723, about the time
when the needle was crossing this line,
as seen in the table above, found the
daily variation to range 30', the amount
we found above as the mean range in the
northern hemisphere. Dr. Bache adds,
page 12: "At, (and before and after) the
principal maximum (of the annular varia-
tion) between six and seven in the
morning, the annular vibration causes
the north end of the needle to be deflect-
ed to the east in summer, and to the
west in winter; at one p.m. the deflection
is to the east in winter and to the west
in summer. The range of the diurnal
motion is thus increased in summer, and
diminished in winter; the magnet being
deflected in summer more to the east in
the morning hours, and more to the west
in the afternoon hours, or having greater
elongation than it would have if the sun
moved in the equator. In winter the
converse is the case." He also says,
page 13, in reference to the annular
variation, that Gen. Sabine expresses
himself as follows: "Thus, in each
hemisphere, the annual deflections —
those that change with the declination of
the sun — concur with those of the mean
annular variation for half the year, and
consequently augment them, and oppose,
and diminish them in the other half. At
the magnetic equator, there is no
mean diurnal variation; but in each half
year the alternate phases of the sun's
annual inequality constitute a diurnal
variation, of which the range in each
day is about 3' or 4', taking place every
day in the year except about the equi-
noxes; the march of the diurnal variation
being from the east in the forenoon to
the west in the afternoon, when the sun
has north declination, and the reverse
when south declination." According to
the same authority (Gen. Sabine), the
annular variation is the same in both
hemispheres, the north end of the mag-
net being deflected to the east in the
forenoon, the sun having north declina-
tion, while in the diurnal variation, the
north end of the magnet, at that time of
the day, is deflected to the east in the
northern hemisphere. In other words,
in regard to direction, the law of the
annular variation is the same, and that
of the diurnal the opposite, in passing
from the northern to the southern
hemispheres.
Now, since I showed that the diurnal
variation is of the same extent as the
annular steps of the secular variation, we
only gain half a day's motion of the sun
in a whole year; for as the direction of
the needle's motion in the night is to us
in opposite direction to what it is in the
day, so the secular motion in the south-
ern hemisphere is contrary to that in the
northern hemisphere, so as to cause the
yearly variation to help the diurnal, and
so augment the secular in the northern
to the amount of nearly 4', as showed
before, which is the range of the yearly
variation about the magnetic equator;
so the secular swing of the needle in the
northern hemisphere becomes 34' per
year nearly. Now, 180° — the whole
swing from tropic to tropic — divided by
34 = 318 years, the secular period of a,
whole vibration in the northern hemi-
sphere, which is the very period given by
Dr. A. M. Mayer in that celebrated
lecture, "The Earth a Great Magnet,"
alluded to before. As to the reason why
the secular swing of the needle appears
to follow the law of a pendulum swing-
ing about the center of gravity of the
earth, is, that while the needle describes
those parts of its orbit about the eastern
and western tropics, its motion is nearly
THE MAGNETIC NEEDLE.
417
in the direction of the line of our vision.
As the needle advances in its orbit, the
course of its swing makes a greater
angle with that line, so as to appear to
move swifter and swifter, until it arrives
at the meridian of the station; where its
sweep is at right angles to our vision
line, and its velocity appears the greatest
of all.
OF THE SECULAR MOVEMENT OF THE
MAGNETIC NODES.
This motion may be termed "the most
grand magnetic vibration." Since the
magnetic needle in all of its movements
respects the apparent motions of the sun,
I thought it worthy of remark, that,
from the phenomenon termed "the
precession of the equinoxes," the nodes
of the sun, or points where his path in
the heavens cut the equinoctial, recede
westward through the constellations of
the zodiac, at the rate of about 50 sec. a
year, which in connection with the east-
ward movement of the line of the
apsides— 12 sec. a year — performs a
grand revolution in about 21,000 years;
as the axis of the sun is thus carried
westward around the earth, the magnetic
nodes, or points where the sun's equator
cuts the terrestrial, should also move at
the same rate and in the same direction
on the terrestrial equator, and so describe
the same grand revolution from east to
west in that vast period. And, not
more strange than true, philosophers,
long ago, observed this to be actually
the case, though they could not account
for it.
Sir Wm. Snow Harris, in the volume
before alluded to, page 266, has the
following remarkable expression: "By a
careful analysis of the observations
recorded at long intervals of time, the
nodes, or points of intersection of the
magnetic and terrestrial equators, have
a slow westerly movement."
OF THE SECULAR VARIATION IN THE
INCLINATION, OR DIP OF THE MAG-
NETIC NEEDLE.
From what has been explained with
regard to the declination of the magnet-
ic needle, it is evident that when such a
needle is set to move freely, it always
rests with its axis in the plane of the
axis of the sun; which, as before demon-
strated, revolves around the axis of the
Vol. XIX.— No. 5—27
earth, in an orbit that declines from it
by an angle of about 16°.
Now, if the earth were to revolve in
the plane of the sun's equator, or that
of any of its parallels, the dip of the
needle would be always the same, in the
same terrestrial latitude. But since the
earth's orbit inclines to the sun's
equator, and so the earth appears some-
times below, and sometimes above that
plane, the magnetic pole of the earth,
which is in juxtaposition to the pole of
the sun, must appear to move alternately
up and down on our meridians, according
to what part of the orbit the sun appears
to describe. And it is worthy of remark,
that this phenomenon had long ago been
observed by scientists to really exist,
and termed " the secular variation of the
dip of the needle." Though this pheno-
menon had been observed, the rate of its
motion from time to time being watched,
and its effect on the magnetic force and
the movements of the isoclinal lines of
the earth accurately determined by
scientists, yet the extent of its vibration,
the length of its period and the place of
its tropics, had not been discovered by
them.
Gen. Sabine observes, that it had been
expected by many that the secular period
of the dip's variation, whieh was then
decreasing, would synchronize with that
of the declination, and that the dipping
needle would also come to its tropic in
1818; and that the dip would commence
to augment from that period. But the
philosophers had been disappointed in
their expectation; the needle is still
descending — the dip is still decreasing in
the British Isles.
Now, the true amount of the variation
of the needle from its mean at any sta-
tion, is the same as the inclination of the
axis of the ecliptic to that of the sun,
which had been given before as 1° 20'.
And since the needle always rests with
its length in the plane of the solar axis,
one might infer that its period is the
same as that of the secular variation of
the declination needle.
There is, to appearance, a vast disa-
greement between the periods of these
two phenomena, but, by my theory,
they should correspond; and, indeed, if
we scrutinize their movement, there is
the utmost correspondence — they exactly
synchronize. The mistake remained, in
418
van nostrand's engineering magazine.
taking the meridian of London, for the
goal to be sought for by the needle,
instead of the prime meridian, or axis
that passes through the intersection of
the two equators.
The last period of the maximum of the
inclination, or when the dipping needle
came to its upper station, occurred in
1723, when the dip was 74° 42' at Lon-
don; this I call the upper transit of the
needle over the prime meridian, where
the dip is the greatest, from where the
needle commences to fall, and the inclin-
ation diminishes in value for the space of
7° 20'. Now, if we consult the table
given elsewhere, we will find that this
year, (1723), was the very year the
declination needle came to a coincidence
with the prime meridian, where its
declination to the true meridian was 16°
7', and where the rate per year of its
secular movement was the greatest of all.
By 1840, according to the observations
made at Kew, the dip was 69° 12', the
difference in 116.7 years being 5° 28'
nearly, equivalent to an uniform diminu-
tion of 2' 8 sec. annually, and Gen.
Sabine observes that the rate of the
diminution of the dip in London had not
materially changed for the last 150 years.
The grand vibration of the declination
needle, according to Dr. Mayer, is made
in 318 years, half of which is 159 years,
this multiply by 2.8 = 445', or 7° 25', the
arc through which the needle falls, which
is nearly equal to the given inclination
of the ecliptic to the solar equator, 7° 20'.
And I think the former is the most true
measure of the latter, for it is evident,
even if the latter was formerly correct,
that as the inclination of the ecliptic to
the earth's equator diminishes, its inclin-
ation to the sun's equator must increase
by the same amount. Thus we see, that
the secular period of the dipping needle
is also the period of the declination
needle; they were together on the prime
axis in 1723, and will again meet on the
same line in 1882. for 1723 + 159 = 1882,
when the dip will begin to increase again.
I may here remark that to the east of
the prime meridian, both the declination
and the inclination of the needle increase
in value till the needle arrives at its
upper transit, whence, in describing the
western hemisphere, they both decrease
again.
One thing I have taken for granted in
the above discussion — that the dip of the
magnetic needle is double that of its
magnetic latitude at any station — and as
some modern scientists dispute the truth
of this principle, and the propriety of its
application to terrestrial magnetism, I
shall make a few remarks thereon.
A few years ago, I independently
discovered that the angular dip of the
magnetic needle is double that of the
magnetic latitude at the same station;
but have since found that Mr. Kroft, of
St. Petersburg, had long before deduced
this law from his observation, and that
Mr. Barlow, of England, subsequently
arrived at a similar deduction by experi-
menting on a magnetic sphere of soft
iron; that Biot endorsed it, and has given
a formula for the inclination. I. am
pleased to yield the honor of the dis-
covery to* these wise men. But the
explanation of the cause of this pheno-
menon I have not as yet met with.
It is represented in books, that at the
magnetic pole the dip of the needle is
90,° and so it is to the horizon at that
point; but not so in comparison to the
horizontal needle at the magnetic equa-
tor. For, the earth being a globe, the
position of the needle at the pole is
"parallel" to that on the equator, its
north pole points in the opposite direc-
tion, or it declines from the latter
position by the arc of 180,° or twice 90°
the greatest latitude.
It is a well known principle in optics,
that, when a light is reflected from a
rotating mirror, that the angle of reflec-
tion of a ray is double that of the
rotating mirror, that is, if the mirror be
made to rotate through 45° the reflected
beam would pass through 90°.
If we now suppose the mirror to be a
globe like our earth, it is evident that
moving the beam around the globe from
the equator to the pole would produce
the same effect as causing the plane
mirror to rotate. The same law is
evidently observed by the dipping
needle, in swinging its tail around the
heavens, as it is carried in a free position
from the magnetic equator to its poles.
The Secretary of State for India desires
that the municipality of Bombay would
urge the Government to carry out a sys-
tem of drainage, as that would remove
one source of ill-health and disease.
STUDIES OF THE ARCHITECT AND CIVIL ENGINEER.
419
THE PROGRAMME OF THE STUDIES OF THE ARCHITECT
AND OF THE CIVIL ENGINEER
From " The Builder."
The programme of the International
Congress on Civil Engineering, lately
reproduced in our columns, is not one
that we can regard with entire satis fac- :
tion. As to its merit — as a compendious j
catalogue of the exhibits or contributions i
of any kind brought before the Congress,
we have nothing to say. But we are en- 1
titled to expect that a document of this
nature should form a sort of skeleton
outline of the science of engineering.
As such, especially when drawn up with
the lucidity of phrase and systematic
order which for the most part character-
ize French scientific works, such a paper
might form a contribution of no little
value to the science of higher education.
As it is, however, the gaps and blanks
are almost as conspicuous as the features
illustrated. Thus, there is a head, " Tele-
graphes pneumatiques" but not a word
as to the electric telegraph, or those
wonderful methods now in process of
daily improvement, by means of which
the electric fluid is employed for the
purpose of giving sonorous signals at a
distance; or, in the words of Mr. Spottis-
woode, electricity is converted into
sound. Again, there is a heading
"Inondations: Moyens a leur opposer"
but not a word as to the first essential j
for carrying out any of these methods, j
the hydraulic survey of the district liable
to the floods. Indeed, the whole question
of survey, the very ground-work and |
basis of civil engineering, is omitted
from the French programme.
We hold that a positive injury is
inflicted on scientific education by the j
setting forth of partial details as if they
constituted the whole of any branch of
study. The tendency of the age is to !
run into detail. The division of labor is
a means of acquiring intellectual, as well |
as physical wealth. But the danger of j
losing sight of the whole in elaborate j
detail of the parts is great and urgent, j
Unless the general form of a science or j
art be kept clearly before the attention
of its students, they not only sink into
mere specialists, but work in their
special branches of study with less
advantage than would be the case were
their ideas enlarged, so as to appreciate
the relation of their particular work to
the general advance of the study of
which it is an integral part.
We have been very much struck,
within the past few weeks, with exam-
ples of the mode in which this special-
isation of attention #appears to have
cramped and injured the coup cVoeil of
the architect. It is unnecessary to
indicate localities, further than to say
that we speak of a part of the country
where pure air, noble prospects, good
roads, and comparative sparseness of
population are such as to prevent
unusual inducements for the erection of
private residences of a high class.
Beautiful specimens of old English arch-
itecture stud the country, from the
cottage and the farm to the baronial or
knightly mansion. Men are found to
understand these advantages, and to
avail themselves of their existence.
Money, it is certain, is forthcoming with
an unstinted hand. A sort of paradise is
open to the architect.
Yet here we find houses rising at costs
varying from £1,500 to £15,000, or up-
wards, the inspection of which, as their
plans gradually define themselves in
brick, and stone, and mortar, serves to
announce the absence of the architect —
using the term in its highest sense. It is
not that we have to complain of scamp-
ing, or of slovenly work. Quite the
contrary. The details are often admir-
able. But the faults that we lament are
the want of grasp, of breadth of plan,
arid of adapting the methods of the
builder to the special circumstances of
site. Here is a house that we might
take as h. model in many respects, with
the stable-yard crammed — quite unneces-
sarily— so close to the main entrance as
to shut off the garden view, and promise
anything but salubrity to the reception-
rooms, if the stud be more than a cypher.
There we see three or four houses, each,
may be, of some pretension to comfort
and elegance, stuck so heedlessly in one
another's light as to form an ill-adjusted
420
VAN NOSTRAND7 S ENGINEERING MAGAZINE.
block, where there might have been a
picturesque and self-contained group of
residences. In another place we see a
road so diverted as to cram one house
into an ill-shaped triangular garden,
commanded by two roads, while the
attempt to obliterate the old road by the
simple process of planting, without any
reference to the rules of landscape or
other gardening, has brought a bit of
irredeemable Cockneydom into what
was a little while since an elegant and
picturesque country road. In another
place, where at least from £15,000 to
£20,000 must be in course of expendi-
ture, where the she commands a mag-
nificent view, and where the preparations
for a terraced garden denote a great
freedom from any narrow ideas as to
cost, we find, rising in the air, instead of
a noble mansion, a heterogeneous collec-
tion of rooms. A Gothic archway, that
might serve for a church, opens into a
little insignificant low vestibule, which
entirely destroys the raison d'etre of the
gateway. Where a noble oriel window
ought to command a broad and diver-
sified view, a chimney is placed, with a
small square glazed aperture, called by
courtesy a window, on each side. By
the doorway, a shapeless window, which
looks like that of a buttery, is intended,
by some strange caprice, to light a studio
or drawing-room. All the details are
admirable. No doubt some good exam-
ples may be cited for every mullion,
every moulding, perhaps every room.
But whole there is none — only a jumble
of parts — and of parts that are petty
and inappropriate, when the situation
demands the simple and the grand.
Now we cannot doubt that an archi-
tect who, at the same time has so much
and so little of what is required for
excellence in his work as the author of
this design, must be a sufferer from .a
want of that comprehensive, systematic,
subordinated programme for his work,
the want of which we lament in the
Paris programme. Given a site of un-
usual beauty, and far-reaching view, the
first duty of the architect should be so
to arrange the chief rooms, and especi-
ally the windows, of the house as to take
this view as much as possible within —
to make it an unrivalled furniture of the
reception apartments. Secondly, we
might suggest, the idea of making the
edifice a consistent and graceful pile of
buildings, as forming part of the view
from neighboring heights, should not
have been forgotten. But to make use
of such an opportunity for the sole
purpose of reproducing Elizabethan
mullions, thirteenth-century arch and
mouldings, and quaint little windows
out of which no one can look, is, — in our
view of the case, — not only to waste
money, but to sacrifice reputation.
With this view we will attempt to
sketch out something of a rough pro-
gramme of engineering study. Our
work must be, necessarily, tentative and
provisional. But those who may mend
it, not by the criticism or the addition of
mere details, but by giving a greater
roundness, completeness, and system to
the whole, will deserve well of their
professional brethren and pupils.
The business of the engineer, then (to
return to the Paris programme) contains
three main divisions or provinces. These
are (1) survey; (2) physical engineering;
and (3) mechanical engineering. The
head of special or unclassed studies may
be added, provisionally, to include those
pursuits which are in the course of rapid
development, or which have not as yet
been sufficiently advanced to be relega-
ted to their appointed stations in the
completed system of scientific order.
Survey is the basis of the whole science
of engineering. It is either general or
special. It ranges from geodesic opera-
tions of the first magnitude to the care-
ful exclusion of a bit of sappy timber
from a bridge or a door. The antiquity
of the work of the surveyor has very
recently been illustrated in an unexpec-
ted manner. An Assyrian tablet, in
baked clay, has just been translated for
our pages. It is a deed of sale of a plot
of ground, and a plan of the ground in
question is attached. This most ancient
land survey is more than 2,000 years old.
Had the plans of Pome, which were
engraved on marble, been copied in
terra-cotta, we might at this moment
have a more accurate knowledge of the
ancient topography of the Eternal City
than we have of London in the time of
the Conqueror. But it was not till the
end of the last century that a trigono-
metrical survey was generally allowed to
be the only accurate basis for mapping a
country. General Roy began the trig-
STUDIES OF THE ARCHITECT AND CIVIL ENGINEER.
421
onometrical survey of Great Britain by
measuring his famous base on Hounslow
Heath in If 84. In 1802, Major Lambton
commenced the mathematical and geo-
graphical survey of India by measuring
a base-line near Madras. Sir George
Everest extended Lambton's " great arc
series " across the plains of the Ganges,
to the foot of the Himalayas; and when
the vast peninsula had been covered
with a gridiron of triangles, and a second
base was measured in the valley of the
Debra Dur, the difference between the
computed and the measured length was
only f inches. The height of the loftiest
of the Himalayan peaks, named, in fit
tribute to the great surveyor, Mount
Everest, was determined by measure-
ments of angles by the great theodolite
as 29,002 feet above the sea.
Survey, then, forms the first part of
the programme of the study of the
engineer. It includes geodesic survey
proper, or triangulation, with astrono-
mical determinations of salient points;
geographical and topographical delinea-
tion; orography, or the contours of the
country; geological survey; hydrological
survey; and hydrography, or preparation
of charts of coasts and estuaries, includ-
ing soundings and determination of tides
and currents. Land survey is an import-
ant detail, subordinate to topographical
delineation. The shading of hills and
delineation of water-sheds, with the
preparation of physical maps, ranks
under the head of orography. The
survey of buildings, and of quarries,
mines, forests, and other sources of
materials for the engineer and the build-
er, carries the duties of the surveyor to
their limit of detail. We have not
spoken of the pioneer surveyor, whose
duty, though important, is only pro-
visional.
Each branch of physical engineering is
properly based on a branch of survey.
The first call upon the engineer is for
the establishment of communications.
For this purpose, when the first stage of
rough work is passed, the orographical
and topographical surveys furnish the
data. Communications at present are
divided into national and international,
or exterior and interior; divisions which
partly, though not wholly, correspond
with that of communication by land or
by water. For the former, the engineer
has to study the formation of roads?
pavements, tramways, and railways; for
the latter, he has to provide ports and
harbors, to cut canals, and to systema-
tize rivers.
The provision of internal waterways is
closely connected with other branches of
hydraulic engineering, based on hydrau-
lic survey. Among them are drainage
and irrigation — a study which requires
for its completion the survey and regula-
tion of forests and plantations. In the
second place ranks the provision for the
water-supply of urban districts, and,
generally, of the population of the
country. Inseparable from the water-
supply question is that of sewerage,
including the disinfection of its effluent
water. Agricultural engineering must
be considered in detail under a separate
head, but is deeply affected by the
system adopted for irrigation and drain-
age. The details of earthwork, masonry,
timber, ironwork, and other element of
construction, may be grouped together
by the writer or lecturer, but will be
studied practically by the pupil as they
are carried out on the different public
works of which the main characters are
above indicated.
Mining, quarrying, coal-mining, well-
sinking and boring, form a separate
branch of study. It is related, on the
one hand, to forestry and woodcutting;
and, on the other hand, to metallurgy,
smelting, and the making of iron and
steel. The civil here comes into immedi-
ate contact with the mechanical engineer,
whose cradle and school are found in the
vast establishments which add forges to
furnaces, and not only, cast, roll, ham-
mer, and forge, but also, turn, bore, and
plane vast and complex objects of metal.
As the physical engineer gives his
hand to *he mechanical, so does the lat-
ter need much of the knowledge of the
chemist. The study of heat has been
usually regarded as a part of physics;
that is to say, of that remanet of natural
science which has not yet been portioned
out under the name of a special study.
But while, on the one hand, the study of
heat, as far as its production and its
metallurgic effect are concerned, is a
part of industrial chemistry, the deter-
mination of the relation of heat to
motion, which is one of the grandest
strides of recent^ science, renders the
422
VAN nostrand's engineering magazine.
study of caloric a distinct part of
mechanics. The English thermal unit —
called after the name of its discoverer,
Joule's equivalent — determines the equal-
ity of the energy required either to raise
772 lbs. for a foot, or to raise the temper-
ature of 1 lb. of water by one degree of
Fahrenheit's scale. This elevation of
temperature in a pound of water can be
produced by the consumption of half a
grain of carbon. If water descends
freely through a distance of 772 feet, it
acquires from gravity a velocity of 223
feet per second; and if suddenly brought
to rest when moving at this velocity,
would be violently agitated, and raised
one degree Fahrenheit in its tempera-
ture. So intimately connected are
chemical, thermic, and mechanical phe-
nomena. The study of mechanical
engineering may be described as regard-
ing, in the first instance, the application
of natural sources of motion. These are
water, wind, and animal power, to which
the ingenious labors of Capt. John
Ericsson have enabled the engineer to
add the radiant heat of the sun.
The readiness with which the force of
gravity can be utilized by falling water
was perhaps one of the first discoveries
in mechanics. The origin of the water-
wheel is lost in the remoteness of anti-
quity. Still more ancient, no doubt,
were the simplest contrivances employed,
and to this day in use in India, for
raising water for the purpose of irriga-
tion. The construction of water-wheels
— over-shot, breast, or under-shot — of
turbines, or of any other apparatus for
utilizing the mechanical force of a fall
or current of water, is falling into
neglect in our densely-peopled country.
Certainty in command of power is even
more essential to the owner of a large
mill or factory than economy; a,nd steam
is displacing water as a prime motor for
that reason. This is not, however, the
case in America, in Italy, or in some
other localities, where the water-mill is
still a very important care of the engi-
neer. In Great Britain, the disuse of
water as a prime mover is likely to be
fully made up for by its constantly
increasing use as a transmitter of motion.
The accumulator principle is one likely
to exercise very wide development.
Hydraulic rams, presses, gun-carriages,
and second motors of all kinds are daily
in course of new application. And the
pump, with all its numerous applications,
may be studied under this branch of
engineering.
The service of wind as a motor power
is falling still more rapidly into disuse
than that of water. Long lines of wind-
mills may still be seen pumping night
and day, whenever there is a breath of
wind stirring, to drain our eastern low-
lands and fens; but the windmill is
becoming more and more rare as a
feature of English landscape. That use
of the wind which, half a century ago,
was one of the proudest peculiarities of
the Englishman, whose insular home
made him so often a born sailor, has
received a last fatal blow from the open-
ing of the Suez Canal. On the China
trade, until that great waterway was
opened, the sailing clipper ships com-
peted successfully with steamers; the
former passage occupying from 90 to 100
days, as against h<5 to 80 days for the
latter. On this well-known sea-path the
course of the winds could be very clearly
anticipated. But ships now run on the
Australian line which perform a voyage
exceeding 12,000 nautical miles, at an
average speed of 11 or 12 knots, and
consume only 1,500 or 1,600 tons of coal
to drive a weight of 6,000 to 7,000 tons
from port to port. Very few sailing
vessels of any size are now building; and
it is only the yachtsman or the fisherman
who is likely long to spread his sails to
the wind.
The use of compressed air, as a
communicator of motion, however, is
advancing together with that of water.
The ingenious effort made some thirty-
six years ago to avoid the great cost of
the self-traction of the locomotive by a
pneumatic apparatus, failed, not from
mechanical, but from physical causes.
As soon as the air in the tube was
rarified by the action of the air-pumps,
the heat of the earth rushed in, and
restored the tension. Thus, the South
Devon engines were at work, not only in
drawing trains, but in pumping heat out
of the earth; and they became almost
red-hot in consequence. The use of air
as a secondary motor is in its infancy.
In some cases, as in mining and tunnel-
ing, highly compressed air performs the
double function of moving the perfora-
tors, and of ventilating and cooling the
STUDIES OF THE ARCHITECT AND CIVIL ENGINEER.
423
works by its escape. It is probable that
the employment of compressed air will
hereafter receive a great development.
As to the use of animal power, the
great object of the engineer at the
present day is to dispense with its
employment. Among the earliest steps
in civilization may be reckoned the
attachment of the bullock to the plough;
and, much later, that of the horse, not
only to the plough, but to the wagon,
the boat, and the coach. The entire
period comprised in the history of the
application of animal power has witness-
ed an increase in velocity of work or of
transport, from about one mile and a
third to sixteen miles per hour. The
former is the pace of the bullock in the
plough; the latter rate of progress, that
of a horse, at the fastest trot, was attain-
ed by some of the fastest of the English
coaches forty years ago. One great
disadvantage of animal power is that its
cost increases rapidly together with the
speed attained. It is not the work done
which is the limit of expense; but the
wear and tear of the animal tissues.
Each creature has its natural pace, or
rate of movement; and the most rapidly
moving are also the lightest animals, and
those least adapted for performing
mechanical work. With machinery the
reverse is the case. Speed, in machines,
is a great element of cheapness. A
machine driven twice as fast as another
may do twice as much work in the same
time; and although the consumption of
fuel is proportioned to the work done,
much of the other expense will be pro-
portioned to the time occupied in doing
it, so that the financial saving becomes
considerable. Indeed, if experiments
described in the American Journal of
Science and Arts may be relied on,
certain kinds of friction, such as that of
journals, decrease with an increase of
speed in the revolution of the machinery;
a speed of surface revolution of 1 foot
per minute giving 15 as a co-efficient of
friction, and a speed of 100 feet per
minute giving a co-efficient of only five.
This diminution of cost accompanying
increase of speed is an element which
tends to the entire displacement of
animal by mechanical moving power. It
substitutes the steam-engine, or the
caloric-engine, for the bullock or the
horse, as the slave of man. Little by
little it will extinguish the laborer, or
the uninstructed man who derives his
pay from the sheer exercise of muscular
strength. Not a year passes without the
substitution of mechanical power for
human labor in some new field. The
revolution thus in progress is one of
more moment than any that the world
has yet witnessed. Very long was it
stoutly resisted — and resisted by the
very men whose position, it may be
hoped, will be elevated by the removal
of the burden of toil from their shoul-
ders. This fierce opposition has of late
slackened, if not ceased, in this country.
It is now rather felt to be the case, very
often, that necessary work is shirked, or
grudgingly performed, than that ,the
laborer insists on his monopoly of toil.
We here touch on a question in which
the functions of the engineer bring him
into contact with the statistician, with
the statesman, and with the philanthro-
pist. But while in newly settled coun-
tries, and in sparsely peopled districts,
human muscles, and the ready service of
the bullock, the horse, the ass, and even
the llama, may long retain their present
importance as prime movers and sources
of power, there seems every reason to
anticipate that neither water, wind, nor
animal power will be employed as prime
movers, except under rare and exception-
al cases, in the engineering of the future.
To one great exception, however, we
have by-and-by to allude.
We cannot do justice to the subject
without returning to its discussion. But
in closing for the present, we cannot
omit to express lively satisfaction at the
manner in which the appreciation of the
importance of exhaustive and systematic
programmes is evinced by the first
speaker at the meeting of the British
Association. The address of the presi-
dent is one of which every Englishman
may feel proud. Mr. Spottiswoode's
tacit protest against a professedly
positive, but really negative, attempt to
draw a hard-and-fast line to what is to
be known, will receive the support of
every worker in science, as contrasted
with the dreamers in philosophy.
Professor Ingram, in his apology for
political economy, has taken up our own
position — "That the study of the eco-
nomic phenomena of society ought to be
systematically combined with that of the
424
TAN NOSTRAND' S ENGINEERING MAGAZINE.
other aspects of social existence; that
the excessive tendency to abstraction
and to unreal simplification should be
checked ; that the a priori deductive
method should be changed for the his-
torical; and that economic laws and
deductions from them should be ex-
amined, and expressed in less absolute
form.
Nor must we omit, in calling attention
to the accordance between the views we
have long maintained and those now
authoritatively put forth at Dublin, to
congratulate the president of the
Mechanical Sciences Section, Mr. Easton?
C.E., on his advocacy of our own propo-
sal, several times urged, for the creation
of an administrative department "charged
with the duty of collecting and digesting
for use all the facts and knowledge
necessary for a due, comprehensive, and
satisfactory dealing with every river-
basin or water-shed area in the United
Kingdom."
WATER ENGINES Y& AIR ENGINES.
By L. TKASENSTEE, of the University of Liege.
Translated from "Kevue Universelle des Mines" for Van Nostrand's Magazine..
I.
If we take no account of the heating
due to the compression of air, the ratio
of the work restored to the work ex-
pended, is expressed by
E:
1-2-
n
2.303 log. ri
n being the number of atmospheric
pressures.
[N~ote. — The deduction of this formula
is given by M. Trasenster in a former
article, as follows :
Let p = atmospheric pressure per square
meter= 10333 kilos.
P= pressure of the compressed air
v & V=volumes corresponding to above
pressures
~P=np
V=nv
The theoretical work afforded by
compressed air is
Tr =(P-p) v=Fv-pv
but as Yv=pV and V=nv
we shall have
Tr = T?v — pv=p(V—v) = pV(l
Whatever the pressure therefore to
which one cubic meter of air be com-
pressed the work performed by its ex-
pansion will always be less than p XI or
10333 kilogrammeters. To accomplish
this amount of work - must become
n
equal to 0, whence n equal to infinity.
The work of compression is expressed
by the formula
Id =£>V + nep. log. n
and the ratio of work restored to work
expended is as above
1
1 —
E:
■]
pVx 2.303 log. n
If the heat be taken into account the
useful results are still lower and the
losses augment with the pressures.
If c represent the specific heat of air at
constant pressure
& c' represent the specific heat of air at
constant volume
-—£=1.408
c
If p represent pressure and Q the cor-
responding volume, then by Mariotte's
law, pQ is a constant. Also according to
Poisson pQk is a constant
Furthermore the coefficient of dilata-
tion of gases by heat being ^-3=- and
absolute zero being
known relation
273° we have the
273 + T
273 + 2'
©"=(!)-
WATER ENGINES VS. AIR ENGINES.
425
and representing
7c— 1 0.408
= 0.29 by b
k ~ 1.408
we may write the above
273 + T _/P^o.29 /P \b b
273 + t -\p) -\j)-n
From this supposing the initial tem-
perature of the air 10° C we deduce the
following values for temperatures for the
several pressures given
P= 2 atmo., T= 73°
P= 3 " T= 116°
P= 4 " # 150°
P= 7 " 236°
P= 10 " 276°
P= 2
451
If compressed air be expanded a
lowering of the temperature is the result,
the extent of which may be calculated
by the same formula, T representing the
initial and t the final temperature. If
T=10° and the expansion be the result
of diminishing the pressure from 3 to 2,
the value of £ 'becomes —21.4°. If T be
25°, <=-8.1°.
If a volume of air, compressed by
7 atmospheres as at Mont Cenis, and St.
Gothard, be expanded to atmospheric
pressure, we find by the formula
The value of the work restored is
273 + 10 _
273 + t ~
£= — 112
(V)
The work absorbed by the compres-
sion is, taking the temperatures in ac-
count
But we know that
From which we get
T-t
a + t
1
and as
h _1
h—\~~b
we shall have by substitution
E:
T,=*>q(i-±).
y we get for
id to work expei
Consequently we get for the ratio of
work restored to work expended
n° — 1
n a
and substituting for b its value 0.29
0.29(1—-)
7*0-29 — 1
The useful effect decreases as the
pressure increases, and the more rapidly
if we allow the air to heat during com-
pression.
The following table exhibits the dif-
ference of useful effects of 1st, the com-
pressed air cooled and, 2d, the com-
pressed air allowed to retain the heat
due to compression :
Useful effect. Useful effect.
Pressures. Air cooled. Heat retained.
2 atm. 0.72 0.65
3 " 0.61 0.52
4 " 0.54 0.44
0.50 0.39
0.44 0.31
25 " 0.30 0.18
These figures show that not only is
the useful effect diminished as the press-
ure increases, but that the difference be-
tween the performances of these two
conditions augments also.
A pressure of seven atmospheres was
employed in tunneling the Alps, and the
pressure of twenty-five atmospheres has
been recommended by M. Mekarski for
tramway engines.
The effect of heating has been largely
avoided by the use of water spray as em-
ployed by M. M. Colladon, Cornet, and
others. Diagrams obtained under such
conditions differ but little from those re-
quired by Mariotte's law.
It is necessary in order to reduce the
loss of work to a minimum to employ the
expansive force of the air without so
great loss of heat ; but the problem pre-
sents great difficulties.
M. Cornet who has given much atten-
tion to all the practical questions relative
426
VAN NOSTR AND' S ENGINEERING MAGAZINE.
to compressed air, has suggested the use
of an injection of water at the tempera-
ture of the mines. It has also been pro-
posed to heat the outside of the cylinder,
a plan of slight efficiency. Finally it
has been proposed to employ, in con-
nection with the compressed air, water
heated to a high pressure.
II.
EMPLOYMENT OF WATER AT HIGH PRESS-
URE.
Compressed air possesses exceptional
advantages as a motor for machines
working at high velocities in shafts and
galleries of mines. Its use, however, in-
volves an expensive equipment, and it is
rare that more than a third of the power
of the compressing engine is realized in
practice. It is, therefore, not an econo-
mical method of transmitting force to
the depths of mines and tunnels.
Water, by reason of its incompressi-
bility, transmits force without other loss
than sucli as arises from friction. In
mines its weight suffices for an initial
force, without aid of special devices; but
its mass prevents the use of high veloci-
ties in water pressure or piston engines.
It is necessary, therefore, that in con-
ducting pipes it should move with lower
velocities than air or steam.
Notwithstanding the difference in den-
sity and mobility of the two fluids, the
loss of work due to friction in the pipes
can be made as little or less than that
from use of air in two ways :
1st. By increasing the diameter of the
conducting pipes, and thus reducing the
velocity.
2d. By compensating for the diminu-
tion of velocity or volume of the water
by an increase of the effective pressure
without modifying the section of the
conduits.
We know that for a circular conduit
whose length = 5, radius =r and deliver-
ing a volume Q per second, tbe velocity
nr
The head which measures the resist-
ances to this motion is calculated by the
formula,
A:
2c
IV*
or 2 cl
Q!
ment; for gas it is 0.00031; for water it
varies between 0.000356 and 0.000385
according to the velocity, 0.00037 may
be considered a mean value.
The height being thus determined, the
pressure due to this upon a unit of sur-
face is found by multiplying by the
weight of a unit of volume. In other
words, to calculate the pressure to the
square meter it is necessary to multiply
the height which measures the friction
by the weight of a cubic meter of the
fluid.
The weight of a cubic meter of water
is 1000 kilograms. A cubic meter of air
at 0° and pressure of 0m.76 is lk .293.
But the temperature is generally above
this and it moreover contains a quantity
of watery vapor so that the weight of
the meter, under ordinary circumstances,
may be taken at lk.25 corresponding to
a temperature of 9.4° . This is -g-J-g- of
the weight of the same volume of water.
Under a pressure of n atmospheres a
cubic meter of air will then weigh 1.25%
kilograms.
The pressure per square meter for air is
2c O2
hXl.25n=:—lV2Xl.25n=2cl-l-bXl.25n
r n r
and for water,
h! X 1000=-^V'2 X 1000=2c'Hr7j
Equating these values;
xiooo.
The coefficient c is determined by experi-
or
or
— 9^-Xl.25n=-T ^-X1000
n r 7i ■ r
CX1.25W c'1000
0.00031 XL 25w 0.00037X1000
From which we get
r'b 1000 37 800 a ,rt„
— ;= X— = X 1.193.
rb 1.25% 31 n
If fi—4: we find
:r6X200X 1.193
or r'=r V238.6=^X2-989
Whence we see that it will suffice to
triple the radius of the conducting pipe,
in order to insure a circulation of water
through it by the same effort or moving
force as that required for the same vol-
WATER ENGINES VS. AIR ENGINES.
427
ume of air under a pressure of four
atmospheres; a medium -gfo of the dens-
sity of water.
But a better solution of the problem
is obtained in another way.
The ratio of the work lost by friction
in the pipe, to the work afforded by the
water at a pressure of n' atmospheres is
Q'A'IOOO _ A'lOOO
Q'X 10333^ ~ 10333??
The loss then is a fraction which de-
creases as n' increases.
In the case of compressed air the ratio
of work of friction to effective work is
QAX1.25^ 1.25 nh
QX 10333(^—1) 10333(^-1)
7%
It diminishes with the fraction
n — 1
and not with - as in the case of water.
n
But the chief advantage of employing
water at high pressure is that we obtain
the same effective work as with com-
pressed air, with so much less volume
and can, consequently, reduce the
velocity in the supply tubes in like pro-
portion.
The work of a volume Q' of water
under a pressure of n' atmospheres or
7i'p=n'\§Z33 kil. is expressed by
Q'n'p.
If we deduct the work of friction in
the pipe,
QV^-2X 0.372-^
n - r
To make this work equivalent to that
of a volume, Q of air, urged through a
tube of the same dimensions, and with
equal resistances for the two fluids, we
establish the following equations :
1st. Equalizing the energy on entering
the pipe :
Q'n'p=Q(n—l)p
or QV=Q(w-l);
2d. Equalizing the loss from friction
in the pipe :
For water this work is
Q7/xiooo=2xo-,°»03W' .000.
7t T
For air it is
Q/>X1.25. = 2X0r503Wl.25.W
Equating these
Q^Xl.25rc=
or
8x0-,0°081«yi.M»:
Q'A'X 100.0
2X0.00037
X
Q'3X1000
or 3lQ31.25?2=37Q'31000.
we then have
800.
Q3
37 1000
3T!^X^
and
Q:
:Q'V
1.193X — Q'3
n
954.4
For 7i=2
Q = Q'X7.816
Q = Q'X6.828
Q=Q'X6.20
Q = Q'X5.758
Q = Q'X5.419
Q = Q'X5.148
The equation QV=Q (71— 1) gives
Q
71=3
n=4
71=5
n=6
71=7
n
Q
i(»-i).
and consequently
atm.
For n=2 w' = ix 7.816 = 3.91 n or 7.82
n=3 w'=2X«.828=4.55 n or 13.65
7i=4 n' = 3X6.20 =4.65 n or 18.60
7i=5 n' = 4:X 5.758 = 4.61 n or 23.03
n=6 ^' = 5X5.419 = 4.51 n or 27.09
n=1 ^' = 6X5.148 = 4.41 n or 30.89
Thus with pipes of the same diameter,
a volume Q of compressed air, and a
volume Q' of water will yield the same
effective work if
Q
Q'"
V'
954.4
71
if also the pressures n' of the water and
n of the air bear the ratio
s-v
954.4
n
It appears also that to realize this con-
dition that the water pressure should not
exceed 4.65 times the pressure of the
air.
Another point of interest relating to
water pressure or compressed air motors
working in mines, is the influence of the
difference of level between the two ex-
tremities of the conducting pipe.
428
VAN NOSTRAND'S ENGINEERING MAGAZINE.
If we suppose a vertical tube of a
height H; n and N being the respective
air pressures at the two extremities, we
shall have the following relation :
Lo K-1-25xH
°S n ~ 10333
calling 1^ .25 the weight of a cubic meter
of 'air.
But the results of this formula differ
so little from those obtained by consid-
ering the air incompressible, that we
may, for all ordinary cases, calculate the
increase of pressure, per unit of surface,
at considerable depths by estimating the
column of air by i.25+wxH. This is
expressed in atmospheres per square
meter by dividing by 10333
1.25X^xH
or
10333
This for w=4 and H=100 meters is
= 0.0484
consequently T$=n + 0.0484 = 4.0484
the logarithmic formula above gives
N=4.049
a difference of only 0.0006 of an atmos-
phere for a difference of level of 100
meters.
For 1000 meters the formulas give re-
spectively for values of N; 4.484 and
4.516; a difference of only 0.032 of an
atmosphere.
We may then in applying the formula
to mines treat the air as we do water,
and consider the augmentation of press-
ure at the bottom as due to the weight
of a column of fluid of the same density
throughout.
So that for a column of vertical height
H we have for pressure per square metre
due to height,
for air Hxi.25Xw
for water HX1000
This pressure is reduced, 1st, by the
friction of the fluids; and, 2d, by the
counteracting pressure of the atmosphere
or rather of the increase of atmospheric
column. This latter would be the same
for both kinds of motor and would be
equal very nearly to 1.25 H kilograms
per square meter.
The resistance due to friction is for
the air, represented by a column equal to
2c
-HV2,
r
and by a pressure equal to
-HV2X1.25^
r
For the pressure lost would be equal
to
— HV2X1000,
r
the velocity t V being the same in both
cases.
Consequently the pressures, after
making the deductions, would be
For air
HX1.25 w(l--V2)-Hxl.25.
For water
HX1000 (l-^V2)-Hxl.25.
If we make
n=49 V=l and r=0.10,
we shall have the effective pressure, for
air,
5H(l-0.0062)-1.25 H=H(5X0.99S8
-1.25)=Hx3.7l9
and for water,
HX1000(1 — 0.0074) — 1.25H=H(992.6
— 1.25)=HX991.35.
If H=100 we shall for pressure per
square meter, due to difference of level;
for the air 371.9 kil. which for V=l and
r=0.10 would represent a supplementary
work of 371.9X0.0314 = 11.68 kilogram- "
meters, or 0.156 horse-power.
With water the supplementary work
for the same conditions would be :
99135X0.0314 = 3112.82 km .
= 41.50 horse-powers or 266 times as
much as from the same volume of air at
four atmospheres pressure.
For a pipe of 0m.05 radius and a
velocity of one meter, the effective work
of water at 100 meters becomes 10.3
horse-power; at 400 meters it becomes
41.2, and if for this depth the radius is
made 0m.10 the effective work=166
horse-power.
It is true that in most cases the water
used for such purpose in mines would re-
quire pumping out again; but this re-
quires no unusual equipment. The drain-
age of mines by pumping engines is a
constant factor of mine working. These
engines are usually steam pumps yield-
WATER ENGINES VS. AIR ENGINES.
429
ing an efficiency of 75 to 80 per cent, of
the power of the engine.
Compressed air, on the other hand re-
quires for the compression, a special ap-
paratus, in which not more than a third
of the work is rendered effective.
The greater pressures required for
water motors would demand stronger
and more costly tubes. But it may be
added that in working the galleries of
mines a descent of the water from the
motor to the well of the drain pump
would frequently afford a source of
power.
A recapitulation of the foregoing
is exhibited in the following formulas :
The effective work of air compressed
without heating is
E=.
1-1
n
and
E=
2.3 log n
,0.29
the
when we consider the air heated to
full extent due to the compression.
Water meets in the pipes greater re-
sistances than air; but for the same vol-
ume transmitted the loss of work from
this cause is the same for the two fluids
if the radii of the conduits have the
ratio :
r V i2
93 m
,25n;
the weight of the cubic meter of air be-
ing 1.25 kil.
Both air and water in conduits of the
same diameter yield the same effective
work at the ends if the volumes Q and
Q' and the pressures n and n' bear the
following proportions :
Finally, in a descending column the
increase of useful pressure per square
meter due to the weight of the fluid is,
for a height H and velocity V,
for air
,(
Hxl.25
and for water
/ 0.
HxlOOOUl
0.00062.
00074,
H.1.25
2)-H.l.
25.
We may conclude then that although
compressed air possesses undoubted ad-
vantages as a motive power in mines,
where machines run with a high velocity
and a shock, as do the several drilling
machines, for ordinary service the high
pressure water engines are preferable on
the score of efficiency and economy.
THE MOST ANCIENT LAND SURVEY IN THE WOKLD.
From "The Building News."
Herodotus, the father of history, tells
us that the science of geometry origi-
nated in Egypt, where the practice of
land-surveying was first rendered neces-
sary by the frequent obliteration of land-
marks, through the periodical overflows
of the river Nile. Plato ascribes the in-
vention of geometry to Thoth. Iam-
blichus says that it was known in Egypt
during the reign of the Gods; and Eusta-
thius, in speaking of an age long before
the Greeks were sufficiently advanced to
study or practice the art, says that the
Egyptians "recorded their march in
maps, which were not only given to their
own people, but to the Scythians also, to
their great astonishment." The frequent
changes of surface must have rendered
the land-surveyors' a rather busy profes-
sion in ancient Egypt, and a considerable
body of them were employed by Rameses
III., whose office is thus described by
Herodotus : " If the river carried away
any portion of a man's lot, he appeared
before the king and related what had
happened, upon which the king sent per-
sons to examine, and determine by meas-
urement the exact extent of the loss;
430
VAN nostrand's engineering magazine.
and thenceforth only such a rent was
demanded of him as was proportionate
to the reduced size of his land. From
this practice, I think, geometry first
came to be known in Egypt, whence it
passed into Greece." Whether these
ancient land-surveyors' made plans of
the land they measured we cannot say,
because among the copious records of
Egypt no agricultural plans, so far as
we can at present remember, have yet
been found. There are some plans re-
maining of royal tombs, with dimensions
carefully figured in cubits, and also of
the turquoise mines of Wadi-Magarah,
fac-similes of which have been published
by the German Egyptologist, Dr. Lep-
sius; and there are verbal records of the
boundaries of particular lands, but none
of the maps mentioned by Eustathius, or
of those which possibly were drawn by
the surveyors of Rameses or their suc-
cessors.
Discoveries recently made, however,
at the British Museum among the cunei-
form inscriptions on the terra-cotta
tablets of ancient Babylon render it
questionable whether the Babylonians
should not have at least equal credit
with the Egyptians, for the discovery of
the science of geometry, and of its ap-
plication to land surveying and the de-
lineation of plans. The country between
the Euphrates and the Tigris was very
early inhabited by a land-owning popu-
lation, and was subject to the same vicis
situdes of periodical overflow by the
rivers as Egypt; and like circumstances
produced similar effects upon their pro-
gress in science and arts. Laws for the
regulation of property in land may be
traced as far back as the days of the
Kassite kings, b.c. 1656, which are writ-
ten in the very earliest Turanian, or Ac-
cadian, dialect of the country, and which
have just been translated by Mr. St.
Chad Boscawen. Several curious par-
ticulars are found in these most ancient
tablets. For example, it appears most
clearly that the women of Babylonia
could hold real property, that land could
be mortgaged, and that it could be
pledged, together with other things
which modern civilization does not
allow. Thus one tablet says : " His
house, his grove, his field, his slaves,
male and female, for silver he has
pledged." We learn also that the in-
terest charged upon these transactions
was often as much as 30, and sometimes
even 70 per cent.
The actual definition of the boundaries
of land was effected in Baylonia by
boundary stones, on which were carved
not merely a statement of the boundaries,
but words which constituted the stone
itself the actual deed of gift or sale.
One of the most noticeable of these
boundary stones in the British Museum
is a large stone bearing an inscription of
Merodach-baladan I., b.c. 1200, presented
by the proprietors of the Daily Tele-
graph. It records a gift by the King of
a plot of land to a person named Mero-
dachsum Izakir, as a reward for political
services. It gives no dimensions, but
carefufly describes all adjoining proper-
ties, and is attested by many witnesses.
Another conical black stone, dated b.c.
1150, is extremely interesting, as giving
the price paid for the purchase of the
field — viz., 616 mana of silver; but inas-
much as this price was paid in kind, not
in cash, wre have an enumeration of the
different articles, with their respective
values, among which are : " One chariot,
with its harness, for 100 silver; six riding
horses, equal to 300 of silver; a cow in
calf, some asses and mules, as well as
numerous pieces of cloth." This stone
also gives us the name of the ancient
land-surveyor, who. not only defined the
boundaries, but also assessed the value of
all these chariots, cows and calves, and
asses and mules. Let the land-surveyors
of the 19th century learn to reverence
the name of this man, who, until Mr.
Boscawen unearths some still older tab-
let, must remain the father of their art.
His name was Sapiku, the son of Mero-
dach-baladhu, and he is expressly called
Masakhu, the field -measurer.
The number of documents (that is,
terra-cotta tablets) which the Museum
now possesses in relation to the commer-
cial and land transactions of ancient
Babylon and of Assyria is very great, a
collection of more than 2,000 having
been purchased at Baghdad in 1875.
Mr. Boscawen published an account of
some of these last year in a literary con-
temporary,* showing that they formed a
tolerably complete record of the business
transactions of a great Babylonian, firm,
The Academy.
THE MOST ANCIENT LAND SURVEY IN THE WORLD.
431
who traded under the name of Egibi &
Sons, as bankers and state land agents.
Their records relate to every kind of
transaction — land sales and leases, loans
of money, mortgages, sales of slaves, and
dealings in all kinds of property — and
the documents show that they traded in
this manner from the first year of Nebu-
chadnezzar, b.c. 605, till the last of
Darius Hystaspes, b.c. 480, a period of
about 120 years. There are many in-
teresting facts as to the daily life of the
ancient people to be gathered from them,
but that which it is our present purpose
only to notice is the tablet which con-
tains, not simply a description, but an
actual plan of the land referred -to in the
document, just as plans are now drawn
on parchment in the margins of leases.
This, we think we may safely say, is at
present the oldest known land-survey
in the world. It is drawn on a tablet in
dark terra cotta, about 6 inches by 3£
inches, and represents a plot of land
about 8j acres in area. The inscription
at the top informs us that it is the plan
of " A field in the high road on the banks
of the river or canal," Nahr Banituv.
The name of the river, however, is ob-
literated, and its place has been supplied
by Mr. Boscawen from information
drawn from other tablets relating to ad-
joining property. The estate is divided
into three pairs of parallelograms, to
which are added two more similar-
shaped plots, and an irregular trapezoidal
piece. The dimensions are all given in
cubits, or fractions of cubits, most care-
fully figured on the drawing. Taking
the Babylonian cubit as 20.475 English
inches, the greatest length of the estate
would be, from north to south, 1646
cubits, or 936 yards 0 feet 5 inches
English. The width on the northern
border on the edge of the highway is 84
cubits— 140 feet. The dimensions on
the southern part being much defaced, it
is difficult to ascertain the length of the
base line. On the east side the curve
is most carefully measured, its circum-
ference being 120 cubits, or 200 feet. A
small dimension has been marked in the
interior of the arc, which evidently rep-
resented its radius, but it is unfortunately
obliterated. The northern boundary is
the highway, or, as it is called in another
document, "the royal highway." (It is
interesting to notice such a very ancient
use of our present common phrase, " the
king's highway.") The western side ad-
joins the lands of Ipriya and Buruga, the
son of Taria, the son of the Chief
Builder, and this latter person is the
owner also of the land on the southern
boundary. The eastern side and the
upper portion adjoin the lands of Nabu-
sar-ibni, and another portion adjoins the
lands of Kasiya, the son of Dibzir, the
son of Pitu-sar-babi. It would seem
strange for a modern surveyor to mark
upon his plan, not only the name of his
client's neighbors, but those of their
fathers and grandfathers, yet this prac-
tice has revealed to us the fact that the
ancient Babylonian " Chief Builder," or
architect, was a person of some conse-
quence, who left lands behind him, and
grandchildren to be proud of their de-
scent from him; and not the serf, or ser-
vant, which he was mistakenly re present-
ed to be in one famous modern picture.
As an example of the system of men-
suration, and curious method of computa-
tion of the area, which was according to
the amount of corn seed required to sow
it, we make the following extract from a
tablet dated in the third year of Naboni-
dus, king of Babylon :
1. 949 cubits on the upper side towards the
west a boundary is fixed.
2. By [the land of] Nabu-sum-utsir, the giver
of the field.
3. 949 cubits on the lower side towards the
east the boundary is fixed by the land of
Nabu-sar-ibni, son of Marducu.
4. 40 cubits the upper headland, a boundary
line is fixed by the king's highway on the
bank of the canal of Banituv.
5 40 cubits the lower headland, a boundary is
fixed by the other portion of the field.
6. For this field, and this portion, five meas-
ures of corn seed. A field with the wells
attached.
7. A valuation of 5 epha., 8 measures of corn
seed.
This is the first measurement. •
This represents the measurement and
sowing area of the first portion of the
land sold in the tablet. A second por-
tion which joins on to the southern
border, is also computed by a similar ar-
rangement. A summary of the two re-
sults is given, and the price in silver, ac-
cording to the market value of corn, is
computed and entered as the price of the
land. A guarantee of about one-tenth
per cent, is required and given as security
for the fulfilment of the clauses of the
432
VAN NOSTEAND' S ENGINEERING MAGAZINE.
deed. The names of seven witnesses
who attest the deed, by affixing their
nail-marks, and the scribes, who append
their seals, testify to the legal character
of the document.
Such was the legal procedure in the
conveyance of land 2,500 years ago in
ancient Babylonia. How little it differs
from the legal acts and deeds which are
daily transacted in our modern Babylon
of London, and in this Great Britain
which has just assumed new responsibili-
ties in relation to the old country whence
these antiquities have been exhumed !.
APPARATUS FOR DETERMINING THE RESISTANCE OFFERED
TO SHIPS BY EXPERIMENTS ONj THEIR MODELS.
By A. LETTIERI.
Prom " Rivista marittima," Abstracts published by the Institution of Civil Engineers.
This is an apparatus for experimenting
on the resistance offered to the models of
ships. The inventor considers that the
determination of the resistance encount-
ered by a vessel moving at different
velocities in still water is a most import-
ant question, which has been solved by
Mr. Froude. The law which this gentle-
man has formulated, by which to de-
duce the resistances met by a vessel
from those encountered by its model,
Signor Lettieri considers to have been
fully verified by the experiments made
by Mr. Froude on the " Greyhound " and
its model.
The further prosecution of similar ex-
periments Signor Lettieri thinks useful,
or even necessary, with the view of as-
certaining, before the launch of a vessel,
the curve of the resistance that it will
encounter with different loads and dis-
placements. Being unacquainted with
the apparatus used by Mr. Froude, Sig-
nor Lettieri has invented one of his own,
the description of which he illustrates
with a drawing.
In experiments of this nature the ele-
ments to be determined are two : the
uniform velocity, and the resistance en-
countered at that velocity. The first of
these is obtained by the measurement of
the space passed through in a unit of
time. It is, therefore, desirable to have
an apparatus which shall graphically de-
note this velocity by a curve, and refer
it to a measure of the resistance.
To effect this, Signor Lettieri has de-
signed a vertical cylinder (the drawing
■shows the length to be fourteen times
the diameter, but neither scale nor di-
mensions are given), which revolves on
a fixed axis. The upper part of this
axis sustains a pulley, and a second pul-
ley is fixed beneath the cylinder, with a
small drum on its axis. A line attached
to the drum passes over the upper pul-
ley, and sustains a scale pan, to which
is fixed a pencil, the point of which
presses against the cylinder. The model
is attached by a line to the lower pulley,
so that the descent of the weight cor-
responds to the movement of the model
through the water; while the weight it-
self is a measure of the resistance.
Movement is given to the vertical cylin-
der by means of a pair of conically
toothed wheels, one of which is attached
to the cylinder itself. The motion of
the latter being thus made uniform, and
its velocity known, the curve traced on
it by the pencil will indicate the relation
between the movement of the model and
that of the cylinder, and will form a
regular spiral when both movements are
uniform. The remainder of the Paper is
occupied by an algebraical investigation
of the curves thus to be obtained, and by
the relation between the weight placed
in the scale pan, and the resistance en-
countered by the model in its passage
through the water.
Fifty sailors were placed in one of Mr.
Berthon's twenty-eight feet collapsing
boats at Portsmouth, for the purpose of
testing it. The sea was very lumpy, but
the boat, which is capable of carrying
eighty men, behaved perfectly to the
satisfaction of those under whose super-
intendence the trial was made.
MECHANICAL CONVERSION OF MOTION.
433
MECHANICAL CONVERSION OF MOTION.
By GEORGE BRUCE HALSTED.
Contributed to Van Nostrand's Magazine.
CAUSE AND DESIGN OF THIS PAPER.
By mathematicians in the last four
years has been created a branch of their
science, which is so practical that it
seems as if its results need only to be
put before mechanicians in order to
produce very important applications.
The fact that these results have been,
and could have been, attained only by
mathematicians, has tended, we fear, to
frighten away practical men from a sub-
ject, of which a great part is capable of
being so simply put as to furnish at once
a new and beautiful weapon in the field
of mechanical contrivance. This should
be of especial interest in America, the
land of practical applications ; and so
we have attempted to bring here into
connection the new achievements with
some of the old ones they seem suited to
supersede, confidently leaving the rest to
that sharp-sighted ingenuity for which
our land is famous.
HISTORICAL INTRODUCTION.
No way is perhaps better fitted to
pleasantly awaken interest than the pre-
fixing of a slight historical sketch of a
chapter of progress, which seems to
furnish a very beautiful example of how
the torch of science is passed from hand
to hand, from land to land.
It does not need an expert to appre-
ciate the theoretical interest and practi-
cal importance of being able to draw a
straight line, or convert a straight thrust
into circular motion, and vice versa/ yet
perhaps one not acquainted with the
subject will feel somewhat incredulous,
when told that this was never accurately
accomplished before the year 1864, when
a method of doing it exactly was dis-
covered by M. Peaucellier, then an officer
in the French army. This method we
intend to present and explain; but
meanwhile we will trace briefly its
history and progress.
EIRST ISOLATED PACT.
He first announced it in general terms,
in the form of a question in the " Nou-
velles Annales de Mathematiques," 1864.
Vol. XIX.— No. 5—28
He did not, however, seem fully to
appreciate the importance of what he
had done; nor did his discovery catch
the attention of any one prepared to see
its value, so it fell into oblivion for six
years.
Yet there was at this very time a great
mathematician, Dr. Tchebicheff, in Rus-
sia, working on this very question, and,
in fact, trying to prove the impossibility
of the exact conversion of circular into
rectilinear motion.
Now, it would be interesting to inves-
tigate how it came about, that in 1870,
only six years after its first discovery,
this wonderful conversion was re-dis-
covered just in the right place, that is, in
Russia, by one of TchebichefE's own
students, named Lipkine.
His professor obtained for this fortu-
nate youth a# substantial reward from
the Russian Government; and this has
since stirred up that most conservative
body, the Institute of France, to confer
its great mechanical prize, the " Prix
Montyon," on Peaucellier, who gave, in
1873, a detailed exposition of his discov-
ery, in the same journal which had
published his first intimation nine years
before.
Meanwhile Lipkine had presented the
theory and description of his apparatus
to the Academy of St. Petersburg in
1871, and exhibited a model of it at the
Vienna Exposition in 1873.
THROUGH RUSSIA TO ENGLAND.
Some months after, Dr. Tchebicheff
I happened to visit England, and there
Prof. Sylvester asked him about the
progress of his proof of the impossibility
of the exact conversion of circular into
rectilinear motion. TchebichefT answered
that, far from being impossible, it had
actually been accomplished, first in
France, and subsequently by a student
in his own class. He then made a rough
diagram of the instrument, which con-
sists of seven links. Shortly after this
interview, Dr. Garcia, the eminent
musician, and inventor of the laryngo-
scope, happened to visit Prof. Sylvester,
434
VAN nostrand's engineering magazine.
and being shown the drawing, brought
under his cloak next morning to the
Professor a model, constructed with
pieces of wood fastened together with
nails as pivots, which, rough as it was,
worked admirably, and drew forth the
most lively expressions of admiration
from some of the most distinguished
members of the Philosophical Club of
the Royal Society.
Soon after, Prof. Sylvester exhibited
the same model in the hall of the
Athenaeum Club to his friend Sir Wm.
Thomson, "who nursed it as if it had
been his own child; and when a motion
was made to relieve him of it, replied,
' No ! I have not had nearly enough of
it: it is the most beautiful thing I have
ever seen in my life.' "
THE DEVELOPED THEORY.
Prof. Sylvester's appreciation carried
itself over from admiration to accom-
plishment. He changed what seemed
an isolated fact into a grand theory. He
proved that every possible algebraical
curve may be described by link-work.
In a lecture before the Royal Institution
he stated that we are able to bring about
any mathematical relation that may be
desired between the distances of two of
the poles of a linkage from a third, and
are thus potentially in possession of a
universal calculating machine.
He exhibited and worked a cubic-root-
extracting machine constructed on this
principle, and claimed to have given the
first really practical solution of the
famous problem proposed by the
ancients, of the duplication or multipli-
cation of the cube.
Fired by this lecture, two young
Englishmen, graduates of Cambridge,
Mr. H. Hart and Mr. A. B. Kempe, took
up the subject, and have been carrying
it on with brilliant success.
SOME RESULTS.
But now, perhaps, the reader begins to
fear that our promise of simplicity was
deceptive, and the subject must be too
complex and difficult for a practical
man.
This is very true in regard to its
purely mathematical side;* but it is
surprising how easily many of the results
* For the literature of the subject, see the complete list
given in my article " Historical Sketch of Exact Rectili-
near Motion," Van Nostrand's Mag., Jan., 1878. '
can be stated and explained to a person
even entirely ignorant of mathematics,
that dreaded science.
In addition to its theoretic interest,
the direct importance of one of its appli-
cations is recognized when we consider,
that in many machines and pieces of
scientific apparatus, it is requisite that
some point or points should move accu-
rately in a straight line with as little
friction as possible. If we are forced to
use as guides planes ground smooth, the
wear and tear produced by the friction
of sliding surfaces, and the deformation
produced by changes of temperature
and varying strains, render it of real con-
sequence to obtain, if possible, some more
accurate and easy method which shall
not involve these objectionable features.
As long ago as 1784, James Watt
made an attempt, which was thus
described by himself in the specification
of a patent: "My second new improve-
ment on the steam-engines consists in
methods of directing the piston-rods,
the pump-rods, and other parts of these
engines, so as to move in perpendicular
or other straight or right lines, without
using the great chains and arches com-
monly fixed to the working beams of the
engine for that purpose; and so as to
enable the engine to act on the working
beams or great levers, both by pushing
and by drawing, or both, in the ascent
or descent of their pistons. . . The prin-
ciple on which I derive a perpendicular
or right-lined motion from a circular or
angular motion, consists in forming
certain combinations of levers moving
upon centers, wherein the deviations
from straight lines of the moving end of
some of these levers are compensated by
similar deviations, but in opposite direc-
tions, of one end of other levers."
f3 ^
m.
2\
MECHANICAL CONVERSION OF MOTION.
435
AB is the working beam of the engine;
PQ the piston-rod or pump-rod, attached
at P to the rod BD, which connects AB
and another bar, CD, movable about a
center at C.
"When the working beam is put in
motion, the point B describes an arc on
the center A, and the point D describes
an arc on the center C; and the convex-
ities of these arcs, lying in opposite
directions, compensate for each other's
variation from a straight line; so that
the point P, at the top of the piston-rod
cr pump-rod which lies between these
convexities, ascends and descends in a
perpendicular or straight line."
This would be most admirable if it
were only true. In reality, the path of
P lies on a figure 8, no part of which is
straight; and it has been demonstrated
that no combination of less than five
links can enable us to get an accurate
straight line, however short; while
here, as we see, there are only three
links, namely, AB, BD, DC.
The imperfection of Watt's movement
led to other three-bar attempts and
closer approximations; but with three
bars it can never be solved. Still, if the
swing of the beam of an engine be kept
comparatively very small, the error will
not be great; and so this Watt's Parallel
Motion can be used, and we think still is
used in the majority of English beam-
engines, instead of the guides more
usually employed in this country. That
the guides can, however, thus continue
successfully to compete with it, seems to
us to depend upon the fact that it is
necessarily inaccurate; and we see no
reason why both should not be super-
seded by an application of one of the
perfect rectilinear motions we desire to
present.
FIRST ACCURATE SOLUTION.
The first accurate solution, as we have
seen, was that of M. Peaucellier, in
which seven links are used.
It consists of a rhombus composed of
four equal links movably jointed at
BCDE, and two other links movably
pivoted at the fixed point A and at two
opposite extremities BC of the rhombus.
Take now an extra link FD, and pivot
it to a fixed point whose distance from
the first fixed point A is equal to the
length of the extra link, whose other
end is then pivoted to one of the free
angles D of the rhombus. The opposite
point E will now accurately describe a
straight line, however the linkage be
pushed or moved. The points B and C
move in circles with radius AB, and the
point D moves in a circle with radius
FD, while E unvaryingly describes an
absolutely accurate straight line perpen-
dicular to a line joining A and F. So if
we have our power in the form of the
straight push of a piston, we have only to
apply the end of the piston at E to have
this straight push turned into circular
motion at either of the other points we
choose, and this too without the slight-
est tendency to side motion or wobbling,
and consequently without any need of
guides and their consequent friction and
disadvantages. Again, if we have our
power in the form of a circular motion
and wish to transfer it to straight push
or pull — for instance, to work a pump —
we need only apply the circular motion at
B, D, or C, to get perfect rectilinear
motion at E.
PROOF OF ITS PERFECT ACCUEACY.
All this may be rigidly proved by a
little plane geometry as follows:
The angle ADR being always the
angle in a semicircle, is always a right
angle, and therefore the triangles ADR
and AME having the angle at A com-
mon and the angles ADR AME equal,
both being right angles, have conse-
quently their third angles ARD AEM
equal, and the triangles are similar.
Therefore AD : AR : : AM : AE. There-
fore AD . AE=AR . AM, moreover D
may be on the circle.
436
YAN NOSTRAND'S ENGINEERING MAGAZINE.
But AR and AM once taken are
constant, and their product AR.AM is a
constant; so in order to devise a linkage
such that when one of its points D is
moved around in a circle, another of its
points shall always remain on the identi-
cal chosen line EM, and shall conse-
quently accurately describe that line, we
must be able to discover such a linkage
that however it may be moved, the
product of the variable distances AD
and AE shall always be exactly equal to
the constant known product AR.AM,
while in addition the movable point D
always remains on the variable straight
line AE. Now see how beautifully our
linkage answers these difficult require-
ments and gives us the long-desired
solution. On DE, the part of the line
ADE which is exterior to the circle,
construct, using DE as diagonal, any
equilateral rhombus, as for instance
BDCE, of four links jointed together so
as to move easily. Pivot to B and C
the two equal links AB, AC. Now from
the symmetry of this linkage, however it
be moved on its joints, the points A, D,E
always are in a straight line, and the
radius FD keeps the point D always on
the given circle. Drop the perpendicular
BN, and we always have DN=NE.
Now AB2=AN2 + BN2
BE2=EN2 + BN2;
therefore subtracting,
AB2 - BE2=AN2-EN2 = (AN + NjE) .
(AN-NE)=AE.AD,
and since the bars AB and BE once
made are of constant length, therefore
the product AE.AD is constant, however
much the distances AE and AD may
vary individually as D is carried around
the circle. Thus our desires are accom-
plished, and we have a machine for
drawing straight lines, or turning circu-
lar into rectilinear motion, and vice
versa.
A SUCCESSFUL APPLICATION.
Although this motion seems as yet
almost entirely unknown to ordinary
mechanicicans, yet it has been already
applied in a beautiful manner to the
air-engines which are employed to ven-
tilate the Houses of Parliament in
England.
rlhe ease of working and absence of
friction and noise are said to be very
remarkable. Even the workmen there
never tire of admiring their graceful and
silent action. The engines were con-
structed and the Peaucellier apparatus
adapted to them by Mr. Prim, the
engineer to the Houses, of whom Prof.
Sylvester tells the story that, conversing
with him one day, just before the first
engine was to be made, the Professor
happened to mention that he supposed,
of course, Mr. Prim knew that the point
A need not be outside the rhombus but
might be taken inside it, and the two
equal bars thus made very compact.
"Why ! you don't mean to say so I" cried
Mr. Prim. " Is it possible ? Why then I
can work it all from below, and won't
have to knock a hole in the roof, as I
thought I'd have to."
Prof. Sylvester gives this as an illus-
tration of how an engineer of exception-
ally good capacity will not see things
which, to a mathematician appear
perfectly obvious.
MECHANICAL CONVERSION OF MOTION.
437
The form mentioned is given in the
adjoining figure, where A and F are the
fixed points and DF the extra link, the
lettering of the two previous figures
being retained. Omitting the extra'link,
this is called the negative Peaucellier
cell, the one first given being called the
positive cell.
ANOTHEK APPLICATION.
Mr. Penrose, the eminent architect to
St. Paul's Cathedral, has put up a house-
pump worked by a negative Peaucellier
cell, to the great wonderment of the
plumber employed, who could hardly
believe his senses when he saw the sling
attached to the piston-rod moving in a
true vertical line, instead of wobbling,
as usual, from side to side. A sister
pump of the ordinary construction
stands beside it, but the former,
although quite as compact as its neigh-
bor, throws up a considerably larger
head of water with the same sweep of
the handle. Its elegance and the friction-
less ease with which it can be worked
(beauty, as usual, the stamp and seal of
perfection) have made it the pet of the
household.
RECIPROCATING PROPERTY OF CELL.
Now to return to our cell, we see that
its peculiar power depends on the fact
that, however it be deformed, the
product of the varying lengths AD, AE,
always remains constant. If when these
points coincide, the distances AE and
AD be taken equal to one foot and then
the cell be moved again, when AD takes
respectively the lengths 1, -§-, J, J, &c,
then AE will be found to assume the
lengths 1, lj, 2, 3, &o., showing that the
length of one is so governed by the
length of the other that their product
must remain constant.
Now Mr. Hart found that if he took
four bars and made a linkage in which
the adjacent sides are unequal and two
cross as in the figure, and then took four
points on the four links dividing the
distances between the pivots in the same
proportion, those points will always
remain in a straight line and possess the
peculiar property just adverted to, so
that the product AD . AE is constant.
So also is OE.OD, and also AD.DO and
AE.EO. So we see immediately that
we may employ Hart's cell of only four
bars exactly as we employed Peaucellier's
of six bars, and by fixing one of the
points as A, and pivoting our extra link
to another as D, we can get straight line
motion with only five bars, which is the
least number possible, as has been abso-
lutely demonstrated.
THE QUADRUPLANE.
A beautiful and important extension
of this discovery was made at the same
time by Prof. Sylvester and Mr. Kempe.
Prof. Sylvester has given quite an
elaborate description of it, but I use Mr.
Kempe's own words as being simpler.
" If we take the contra-parallelogram of
Mr. Hart and bend the links at the four
points which lie on the same straight
line, through the same angle, the four
points, instead of lying in the same
straight line, will lie at the four angular
points of a parallelogram of constant
angles — two the angle that the bars are
bent through and the other two its
supplement — and of constant area, so
that the product of two adjacent sides is
constant."
If we keep the lettering of the last
figure, take the holes or points in the
middle of the links and bend them
through a right angle as the simplest,
we have the figure here given. The four
holes now lie at the four corners of a
right-angled parallelogram, and the
product of any two adjacent sides, as
AD.AE, is constant.
438
van nostrand's engineering magazine.
It follows that if A be fixed and D
pivoted to the extremity of the extra
link, whose other extremity is always
pivoted to a point equidistant from A
and D, the point E will describe a
straight line differing in direction from
the line it described before the bending
by precisely the same angle the bars
have been bent through, in this chosen
case by a right angle.
By looking at the figure it is seen that
the apparatus, which for simplicity has
been described as formed of four straight
links which are afterwards bent, is really
formed of four plane pieces on which
appropriate points are chosen. This is
why it is called the " Quadruplane " by
Prof. Sylvester, who says: "The quad-
ruplane gives the most general and
available solution of the problem of exact
parallel motion that has been discovered,
or that can exist. I say the most avail-
able, for it is evident, in general, that
piece-work must possess the advantage
of greater firmness and steadiness, from
the more equal distribution of its strains,
over ordinary link- work."
THE PLAGIOGRAPH.
From the ordinary pantagraph familiar
to mechanicians, on application of this
same idea, namely, turning two of its
links into pieces or planes, gives a beau-
tiful extension of it, called by Prof. Syl-
vester, its inventor, the Plagiograph.
"Like the pantagraph, it will enlarge or
reduce figures; but it will do more, it
will turn them through any required
angle." Thus the Plagiograph enables
us to apply the principle of angular
repetition (as, for instance, in making an
ellipse with dimensions either fixed or
varying it will, successively turn its axis
to all points of the compass), to produce
designs of complicated and captivating
symmetry from any simple pattern or
natural form, such as a flower or sprig.
This should be found to place a new and
powerful implement in the hand of the
pattern-designer and architectural decor-
ator.
ANOTHER IMPORTANT USE.
Finally, we have seen that in using a
linkage to draw a straight line, the dis-
tance between the fixed pivots must
always be the same as the length of the
extra link. ISTow if this distance is not
the same, the pencil-point describes, not
straight lines, but circles. If the differ-
ence be slight, the circles described will
be of enormous magnitude, decreasing
in size as the difference increases. This
property is of very high importance in
in the mechanical arts for describing
circles of large radius. Prof. Sylvester
cites as example some circular steps out-
side St. Paul's Cathedral, which requiring
repair, Mr. Penrose employed a Peau-
cellier cell to cut out templets in zinc for
the purpose. The radius of the steps is
about 40 feet; but to the great comfort
and delectation of his clerk of the works,
they were able to operate with a radius
of not more than 6 or 7 feet in length.
These are but the simplest of the
innumerable applications contained in,
and immediately suggested by, the new
science of linkage. Only let the practi-
cal mechanician begin to make for him-
self models of those here described, and
we guarantee him a rich harvest of
unlooked for results.
In the words of its founder, " I feel a
strong persuasion that when the inertia
of our operative classes shall have been
overcome, this application will prove to
be but the signal, the first stroke of the
tocsin, of an entire revolution to be
wrought in every branch of construction."
It is well for those who manufacture
articles liable to decomposition to know
that glycerine has the power of arresting
fermentation to a remarkable degree. It
is stated in the Chemical Journal that
glycerine retards both lactic and alco-
holic fermentations. One-fifth of glycer-
ine added to milk at a temperature of
15 deg. to 20 deg. C. prevents it from
turning sour for eight or ten days. One-
half or one-third of glycerine, at the
same temperature, retarded the fermenta-
tion of milk for six or seven weeks. At
higher temperatures larger quantities are
needed to produce the same results. The
formation of hydrocyanic acid from
amygdaline and emulsine is also retarded
by glycerine. It becomes thus very ser-
viceable in preventing the spoiling of
various lotions. For this reason it is
not unusual to add a small quantity to
the preparation known as milk of roses,
and also to almond paste. With regard
to cosmetics, generally, the use of glycer-
ine in small quantities may be recom-
mended.
OX AERONAUTICS.
439
ON AERONAUTICS.
Bx EICHAED GEENEE, M. E.
Written for Van Xostrand's Engineering Magazine.
Loxg before the locomotive and the
steamship were thought of, man cast his
eyes longingly over the vast expanse of
atmosphere above him, and thirsted
after the simple ability which a bird ac-
quires so quickly, and which mankind,
after centuries of study and experiments,
has not even approximated to. Ovid has
told us the tale of the feat of Daedalus
in so natural a manner that we should love
to think of it as a reality and it drives
us on to further thought and experiment.
Archytas is said to have constructed a
flying dove, but we are sorry to opine
that this must be classed among the
legends and traditions rather than the
facts which have come down to us from
those days. There is but one possible
means of rising into and traversing
through the air faster than a bird, as a
crusty but not humorless German pro-
fessor informed us in 1812, and that is
by means of our thoughts, and this too,
after having led us through a work of
600 pages descriptive of aeronautical ex-
periments and apparatus, which is all
very fine but hardly satisfactory.
Since then, as many years have passed
away as there are elements, and we are
to this day as unable to go to China by
any other means than land or sea as we
were then. But is it really true that
this sixty-five years long study and re-
search has been to no purpose ? Have
we not even a clew towards the desired
purpose to be effected ?
Let us see what has been done in all
this time; how the difficulties of the
problem of aeronautics have been met
and treated, and how far man failed and
how far he has been successful.
Primarily, it was desired to produce a
means of rising into the atmosphere.
And so far as this is concerned, the
human mind and ingenuity has experi-
enced a triumph which will be as lasting
as it has been successful.
But, paradoxical as it may seem, this
success has been the means of delaying
the progress of the actual science of
aeronautics to a remarkable degree, as
the popular mind has become engrafted
with the idea that the art and science
of ballooning would ultimately and inev-
itably lead to the solution of the prob-
lem. That this is not the case, we shall
learn from an examination of the history,
construction, principles and results ar-
rived at by the balloon.
The Montgolfier Brothers are generally
and popularly accredited with the in-
vention of the balloon, and in so far as
they were the first to construct such a
thing they are not undeserving of the
credit. But Prof. Charles, the Parisian
physicist, invented and constructed a
hydrogen balloon quite independently of
them, and this tias not been superseded
to this day, while the hot air balloons of
the Alontgolfiers went out of practice a
comparatively short time after their in-
troduction.
The way the Montgolfiers got at their
balloon, was as follows : At Annonay,
in Vivarrais, not far distant from the
very base of the Alps, they owned a
paper mill, and here they had the daily
opportunity of watching the formation of
the clouds on the mountain slopes and
then rising into the air. Both were
scientifically educated; they often con-
versed over the causes of the flight of
the clouds, and presently the thought oc-
curred to them to imitate this natural
phenomenon. But their experiments
were a series of sad failures until Priest-
ley's work on different classes of air and
gases fell into their hands, wherein they
found the possibility of the existence of
leases, much lighter than air, discussed.
It was only a question of enclosing
such gases in a light envelope, but all
trials to effect this with paper, failed.
After many vain experiments, they at
last, in 1782, arrived at the desired re-
sult, but curiously enough, on premises
which were utterly ridiculous. Their
idea was that one of the principal causes
why clouds arise in the air and there re-
main at rest, or are wafted about with-
out falling to the earth, is electricity.
Accordingly, they sought the production
of a gas gifted with electric properties,
and this production they thought to
440
VAN NOSTRAND'S ENGINEERING MAGAZINE.
effect by mixing gas of alkaline proper-
ties with non-alkaline. To this end,
they burned straw and an organic sub-
stance, like wool, which was to produce
the alkaline gases, under a square paper
balloon of about forty cubic feet capacity,
and to their delight, the balloon arose to
the ceiling of the room. That it was
simply the heating of the air in the
balloon which effected its rising they
hadn't the slightest idea. Instead, they
thought to have discovered a new gas
with remarkable properties and gained
many followers, until Saussure, in the
following year, terminated the bitter
controversy which had arisen, by per-
forming the simple experiment of in-
flating a small paper balloon by carefully
inserting a red hot iron into it, and caus-
ing it to rise.
The great desideratum had been ar-
rived at, and now it only remained to
carry the thing into practical execution,
and accordingly, the Montgolfiers built,
in the same year, an apparatus of a
diameter of 38 feet, which weighed 450
lbs., and carried an additional weight of
400 lbs., and on the 4th of June, 1783,
this airship ascended from a public
square in Annonay, to the amazement of
the entire inhabitants of Vivarrais. The
balloon was constructed of linen pieces
simply put together by means of buttons
and buttonholes, lined with paper and
covered with a string net- work. And on
a wire gauze under the opening, ten
pounds of straw and wool were burned.
Unfortunately, the spectacle only lasted
ten minutes, the balloon having risen
1960 feet, and horizontally carried along
7200 feet.
The corporation and inhabitants of
Paris received the news of this exhibition,
and, as is usual with that capital, went
wild over it. The Academy of Science
extended an invitation to the Montgolfiers
to come and repeat the show. But the
excitement was too great to await their
coming, and within a few days, 10,000
francs had been subscribed, and Prof.
Charles, the favorite physical scientist of
the day, an energetic young man, was
commissioned to spend this money in
preparing a balloon sensation for the ex-
cited Parisians.
But Prof. Charles didn't treat the mat-
ter in the light of a public amusement.
In speculations over the Montgolfiers'
mysterious electric gas he didn't lose
any time, but applied himself with
energy to the feasibility of the employ-
ment of hydrogen for the filling of the
balloon. Hydrogen was but little known
then, and the idea of operating with
something like 1000 cubic feet of this
dangerous gas, was an appalling one.
However, Charles went to work fearless-
ly and with a will, and the Robert
Brothers, who were clever mechanicians,
filled his order for a balloon constructed
of fine silk in a short space of time,
finishing the same Aug. 23, 1783. This
huge bubble was filled, on plans entirely
original, by air of a barrel serving for
the taking up of the iron and water used
for the generation of the hydrogen, two
tubes leading through holes cut into the
head, one into the interior of the balloon,
and the other for the introduction of the
sulphuric acid. This rude apparatus
brought up many difficulties, which
threatened the failure of the undertaking.
The heat generated by the action of the
acid upon the iron, converted a large
amount of water into steam, which en-
tered the balloon with the gas and there
condensed. Then, also, sulphureted
hydrogen, finding an entrance into the
balloon, and dissolving in the water
formed on the interior of the envelope,
might prove fatal in attacking the light
fabric. It was necessary, furthermore,
to direct streams of water on the balloon
to cool it off. It took four days to fill a
space of 943 cubic feet about two-thirds
full, and 1000 pounds of iron and 500 of
sulphuric acid, to produce the 35.75 of
hydrogen necessary. But of this 31.75
were lost.
On the 27th of August, at 5 P.M.,
this balloon arose over the heads of
300,000 spectators assembled in the pour-
ing rain on the Champ de Mars. It
maintained a respectable height for
about three quarters of an hour and then
fell to the ground at Econe, containing a
huge rent, owing to Robert having in-
flated it too much; and in the upper
regions, where the air is lighter, the gas
in the balloon of course expanded and
burst its flimsy shell. This balloon
was greeted by the peasants as a huge
monster and hunted to death with pitch-
forks and fire-arms amidst the wildest
excitement.
Whence we see that Prof. Charles is
ON AEKONAUTICS.
441
quite as much entitled to the honor of
the invention of the balloon as the Mont-
golfier Brothers are.
On the 1st of December, 1783, he and
Robert made an ascent, and he was
the second human being that had ever
risen above the level of the highest peaks
on earth. The first was Pilatre de
Rozier, on the 21st of November, but as
Charles had published his intent already
on the 28th of September, before Rozier
had thought of so doing, we must also
give him some credit herein. Rozier's
ascent was made in a clumsy balloon, 63
feet high, of a diameter of 51 feet, and
was of Montgolfier's manufacture. He
met with his death, the penalty of his
aeronautical intrepidity in 1785; the first
victim of the balloon. Charles' balloon
had had a capacity of 9200 cubic feet,
and had been 26 feet in diameter.
Assuming its filling at 6000 cubic feet,
the gas weighs 64.5 lbs., taking the
moisture into consideration, while 6000
cubic feet of air weigh 516 lbs. The
difference is, therefore, 451.5 lbs. As
much less than this figure which the
balloon, with all its accompanying para-
ph analia, weighs, so much will it be
capable of carrying into the bargain.
Had the same balloon been filled with il-
luminating gas, this difference would
have been 38V lbs.
Europe now began to indulge in the
wildest speculations, which ended, un-
happily, for the time being, in smoke.
The excitement passed over like so many
others had.done before them and will do
after them; many had lost their fortunes
and peace of mind in the pursuit of the
subject, and a clever few had become
millionaires.
Since then, the art, if not the science,
of ballooning has become greatly ex-
tended, and over 10,000 ascents have
been made, of which the celebrated
English balloonist, Greene, towards the
end of the year 1849, completed 365. Of
1500 aeronants, but 12 have met with an
untimely death.
The ascent which Gay-Lussac made in
1804 was the most remarkable for the J
facts with which it has enriched science, '
and for the immense height of 23,000
feet above the level of the sea which he
attained. At this height, the barometer
descended to 12.6 inches, and the ther-
mometer, which was 1° C. on the ground, j
was 9° below zero. In these regions,
the dryness was such on the day of Gay-
Lussac's ascent, that hygrometric sub-
stances, such as paper, parchment, <fcc,
became dried and crumpled as if they
had been placed near the fire. The
respiration and circulation of the blood
were accelerated in consequence of the
great rarefaction of the air. Gay-Lus-
| sac's pulse made 120 pulsations in a
I minute, instead of the normal number of
63. At this great height, the sky had a
J very dark blue tint, and an absolute
silence prevailed. Rozier before him
I had also made ascents for scientific pur-
poses, but with no recordworthy results.
One of the most remarkable of ascents
was made by Mr. Glaisher and Mr.
I Core well, Sept. 5, 1861, in a large balloon
! belonging to the latter. This was filled
! with 90,000 cubic feet of coal gas, the
i weight of the load being 600 lbs. After
, 1 hour and 28 minutes, they had reached
! a height of 15,750 feet, and in eleven
| minutes after, a height of 21,000 feet,
the temperature being 10.4° C. below
zero; another eleven minutes, and they
I were 26,200 feet high, with the thermo-
■ meter at 15.2° C. below zero; still an-
| other two minutes, and the height at-
tained was 29,000 feet, and the tempera-
ture 16° C. below zero. At this height,
the rarefaction of the air was so great,
and the cold so intense that Mr. Glaisher
fainted, and could no longer observe.
According to an approximate ^otimation,
the lowest barometric height they at-
tained was 7 inches, which would cor-
respond to an elevation of 36,000 to
37,000 feet.
We have seen that the use of hot air
has given way to that of hydrogen, and
the latter, in many cases, to that of coal
gas, -which is preferred on account of its
being cheaper and more easily obtained.
A balloon of the ordinary dimensions,
which can carry three persons, is about
16 yards high, 12 yards in diameter, and
its volume about 680 cubic yards; with
its accessories, it weighs about 300 lbs.,
and alone, about two-thirds of that
amount. The gas is passed into the
balloon from the reservoir by means of
a flexible tube. The balloon must not
be filled quite full, as the atmospheric
pressure diminishes as it rises, and the
gas inside expanding in consequence of
its elastic force, tends to burst it, as it
442
van nostrand's engineering magazine.
did in the case of Charles' first balloon.
It is sufficient for the ascent if the
weight of the displaced air exceeds that
of the balloon by 8 or 10 lbs.
The rising and falling of the balloon
is easy enough, and if it had not been
long proved by direct experiment, Jules-
Verne has done it for us to our complete
theoretical satisfaction in his interesting
work entitled " Five Weeks in a Balloon."
The aeronaut can tell whether he is
ascending or descending, either by the
barometer or by a long streamer attach-
ed to the car. The ascent is effected by
throwing out the ballast of sand bags as
the occasion requires, and the descent,
by the opening of the safety valve on
the top of the balloon which allows part
of the gas to escape. In so doing, the
aeronaut must bear in mind that he is
sustaining an- irreparable loss, and be
careful how he expends the precious
means.
As far as the horizontal motion of the
balloon is concerned, that is beyond the
power or desirability of the aeronaut;
he becomes the plaything of the winds,
attaining a velocity of from 66.66 to 116.
66 feet per second. Garnerin and Capt.
Sowdon, in 1802, on their trip from Lon-
don to Colchester, in one hour completed
17.5 geographical miles, and Robertson,
at Hamburg, about ten. The colossal
balloon, which, decorated with 3000
colored lamps and a richly gilded crown,
was liberated from the Place Notre
Dame de Paris, in Paris, at 11 P.M.,
Dec. 4, 1804, in honor of the crowning of
Napoleon, hovered over Rome at day-
break. Who will bridle such a velocity ?
The only practical application which
the balloon has experienced is in military
reconnoitering, and this has been effect-
ed with great success at the battle of
Fleurus, in 1794, at Solferino and more
lately in the Franco-Prussian war.
. And that is what has been done in 65
years, as far as the art and science of
ballooning proper is concerned.
In addition, however, much more has
been done, and as nearly much more to
no purpose. The wildest and most im-
probable propositions have been ad-
vanced, and many have attempted to put
these into practical operation. The diffi-
culties, both practical and theoretical,
are innumerable and overwhelming,
whole libraries have been written on the
subject, not a year passes by. without
adding to the literature already at hand,
fortunes have been spent in the construc-
tion of designs and the carrying out of
vague experiments, and that same Champ
de Mars which witnessed the ascent of
the first hydrogen balloon, has since
witnessed countless failures, and on
every one of these occasions, the un-
happy apparatus has been ruthlessly
destroyed by the mob to satiate its dis-
appointment. There was Jacob Degen, a
Viennese horologist, who, in 1812, re-
ceived a good licking at the hands of a
crowd for the failure of his plan; and
then there was Lennox, who, in 1834, ex-
hibited his notorious air-ship, the
"Eagle," 160 feet high by 48 broad, by
63 feet long, capable of carrying 17 per-
sons, in Paris, which was broken into a
thousand pieces by the infuriated specta-
tors. And still we are bid not to des-
pair.
The trouble has been that the pro-
jectors of these flying machines have en-
tirely ignored the voice of science; as
soon as an idea would strike them, with-
out stopping to enquire into its theoreti-
cal correctness, they would immediately
plunge into the execution of their im-
provable schemes without a moment's
deliberation, and the necessary result
was failure.
The balloon has long been abandoned
by scientific men as the foundation to
the solution of the knotty problem. The
most advanced thinkers have turned
their thoughts in an opposite* direction,
and have come to regard flying creatures,
which are all much heavier than atmos-
pheric air, as the true models for flying
machines. An old doctrine is more
readily assailed than uprooted, and, ac-
cordingly, we find the followers of the
new faith met by the assertion that in-
sects and birds have large air cavities
in their interior, that these cavities con-
tain heated air, and that this heated air,
in some mysterious manner, contributes
to, if it does not actually produce, flight.
No argument could be more fallacious.
Many admirable fliers, such as the bats,
have no air-cells, while many birds, like
the apteryx, and several animals never
intended to fly, like the orang-outang,
and a large number of fishes are pro-
vided with them. It may, therefore, be
reasonably concluded that flight is in no
ON AERONAUTICS.
443
way or manner connected with air-cells,
and the best proof that can be adduced
is to be found in the fact that it can be
performed to perfection in their absence.
According to Dr. I. Bell-Pettigrew, the
author of the celebrated work on "Ani-
mal Locomotion," and the scientist who
was among the first of his time to point
out the road to the true solution of the
question of aeronautics, there are five
primary causes on which all attempts
have hitherto wrecked :
First. — The extreme difficulty of the
problem. This very cause has given an
attractive and fascinating air to the
problem, and has hitherto prevented its
calm deliberation.
Secondly. — The incapacity or theoreti-
cal tendencies of those who have devoted
themselves to its elucidation. This cause
is now happily eliminated, and like the
first, will cease to come into considera-
tion under the earnest application of
their thought and time of men like Dr.
Pettigrew to the. subject.
Thirdly. — The great rapidity with
which wings, especially insect wings, are
made to vibrate, and the difficulty ex-
perienced in analyzing their movements.
Fourthly. — The great weight of all
flying things, when compared with a
corresponding volume of air. This diffi-
culty will fade more and more as the
aforementioned one is eliminated by
patient study.
Fifthly. — As we have already stated
in a former part of this paper, the dis-
covery of the balloon, which has retarded
the science of aeronautics, by misleading
men's minds and causing them to look
for a solution of the problem in the em-
ployment of a machine lighter than the
air, and which has no analogue in nature.
But it should be remembered, before con-
demning this circumstance as a difficulty,
that the tendency of the new faith may
be as erroneous in the end as that of the
balloon, and that we have not lost so
much after all, by wasting our time on
the balloon in seeking for our solution,
as we have thereby eliminated a factor
from our equation, so to speak, which
might have given us no little difficulty in
the prosecution of so interesting, import-
ant and so complex a subject.
It should also be remembered that past
experience has taught us that the genius
of the inventor has been quite as im-
portant an element in the engineering in-
stitutions of the past as the research of
the scientist, but, of course, the former is
dependent -in a great degree upon the
latter, and as the scope of that research
progresses and enlarges, so do the in-
ventor's genius open new avenues of
probable success. It is surprising how
much the happy thoughts of the illiterate
have contributed towards the progress of
engineering and industry.
So we find that if we can trust the
new faith, i. e., the solution of the prob-
lem by animal flight, that the third
difficulty aforementioned is the only
practically remaining one. That we may
trust in the new faith, such men as Dr.
Pettigrew heartily and enthusiastically
assure us.
The past trouble with the new faith
was that it has been cultivated, on the
one hand, by profound thinkers, who
have never subjected their theories to
experiments, and, on the other hand, by
uneducated charlatans who have never
subjected their experiments to scientific
theory.
There remain many eminent men who
still advocate the employment of a
machine specifically lighter than air,
whom we may style the balloonists; but
the ideas which they advance have
mostly been practically executed and
found to be absurd. They reason that
the first consideration is to raise the
flyihg-machine, as it is to make a ship or
locomotive go, and that the second con-
sideration is to control this motion. And
that is where they are fundamentally
wrong, as the question cannot be treated
similarly to locomotion on land and sea;
and besides, a hundred examples have
taught us the fallacy of their reasoning.
We must abandon the balloon alto-
gether, as we have endeavored to show.
But the balloonists do not formulate
the only irrational school; a second
modern one is that section of the one
believing that weight is necessary to
flight, which advocates the employment
of rigid inclined planes driven forward
in a straight line, or revolving planes,
i. e., aerial screws.
The other section is more rational, and
most likely the right one, trusting for
elevation and propulsion to the flapping
of wings. This section may be further
subdivided into advocates of the vertical
444
VAIST NOSTEAND'S ENGINEERING MAGAZINE.
flapping of wings, such as Borelli, Marey
and others, and advocates of the parti-
ally horizontal flapping of wings, such
as Bell-Pettigrew. The favorite idea of
the disciples of the inclined plane scheme
is the wedging forward of a rigid in-
clined plane upon the air. It may be
made to advance either in a horizontal
line, or made to rotate in the form of a
screw, whence we also have this section
subdivided, and both divisions have their
adherents. The one recommends a large
supporting area extending on either side
of the weight to be elevated, the surface
of the supporting area making a very
slight angle with the horizon, and the
whole being wedged forward by the ac-
tion of vertical screw propellers. This
was the plan suggested by Henson and
Stringfellow. The former designed his
his aerostat or flying machine, in 1843, and
the latter, on Wengham's plan, exhibited
his design at the Aeronautical Society's
Exhibition, held at the Crystal Palace,
London, in the summer of 1868. These
formidable and scientific-looking things
were never coerced into giving an exhi-
bition of their pretended capacities, and
it were therefore useless to consider
them.
The first to apply the aerial screw to
the air was Sir George Cayley, who, in
1796, constructed a small machine con-
sisting of two corks fastened on either
end of a vertical spindle, to the lower
part of which is suitably secured the
middle of a whalebone bow. To either
end of the latter are attached strings
which wind about the spindle, and thereby
stretch the bow. In the corks are inserted
a number of wing feathers from any
bird, so as to be slightly inclined, like
the sails of a windmill, but in' opposite
directions in each set. This instrument,
after being wound up, readily rises in
the air. Sir Cayley calculated that if the
area of the screw was increased to 200
square feet, and moved by a man, it
would elevate him. But it appears
that he never tried it.
This model was immediately seized
upon as the basis for a flying machine by
a great many people. In 1842, Mr.
Phillips succeeded in elevating, by means
of revolving fans ; a model made entirely
of metal, and which, when complete and
charged, weighed two pounds. The fans
were inclined to the horizon at an anode
of 20°, and through the arms the steam
rushed, on the principle discovered by
Hero, causing the fans to revolve with
great energy, so much so that the model
rose to a great altitude, and flew across
two fields before it alighted. The mo-
tive power employed in this instance was
obtained from the combustion of char-
coal, nitre, and gypsum. This is the
first machine that steam ever raised into
the air.
The French also seized upon the screw
scheme with avidity, and Nadar, Pontin,
d'Amecourt and de la Landelle, between
the years 1853 and 1863, succeeded
in constructing clockwork models, which
not only raised themselves into the air,
but also carried a certain amount of
freight.
It will be readily understood that there
is nothing gained by all these machines,
and that they are even less efficient than
the balloon, and much more costly.
What if you can rise into the air with
them, and ever so high at that? That
is not the question; the question of ris-
ing in the air has been solved by the
balloon; what we want is direction, and
not elevation ; the aerial screw is no more
governable in this regard than is the
balloon.
Whence it appears that we must reject
the doctrines of the inclined plane school
quite as much as those of the balloonists;
and another important and troublesome
factor has been eliminated from our equa-
tion. Let us see how soon we can get it
down to "x equals to."
There now remains to be regarded the
doctrines of those who believe in the
flappings of wings, to secure the desider-
atum.
In 1860, Borelli published at Rome a
two-volume work, "De Motu Animali-
um," and up to 1865, all the knowledge
that we possessed on the subject is due
to this distinguished physiologist and
mathematician. He constructed an arti-
ficial bird in which the wing, consisting
of a rigid spine, with natural feathers
attached thereto, flapped vertically down-
wards, and this idea has been enthusi-
astically seconded by both Straus-Durck-
heim and Girard, and quite lately by
Professor Marey.
Borelli opines that flight results^ from
the application of an inclined plane,
which beats the air, and he evolves,
ON AERONAUTICS.
445
amongst others, the following proposi-
tions from his arguments:
First — If the air strikes the under sur-
face of the wing perpendicularly in a
direction from below upwards, the flexi-
ble portion of the wing will yield in an
upward direction, and form a wedge with
its neighbor.
Secondly — Similarly and conversely,
if the wing strikes the air perpendicu-
larly from above, the posterior and flexi-
ble portion of the wing will yield and
be forced in an upward direction.
Ihirdly — That this upward yielding
of the posterior or flexible margin of the
wing results in and necessitates a hori-
zontal transference of the body of the
bird.
Fourthly — That to sustain a bird in
the air the wings must strike vertically
downwards, as this is the direction in
which a heavy body, if left to itself,
would fall.
Fifthly. — That to propel the bird in a
horizontal direction, the wings must
descend in a perpendicular direction,
and the posterior or flexible portions of
the wing yield in an upward direction,
and in such a manner as virtually to
communicate an oblique action to them.
Sixthly. — That the feathers of . the
wing are bent in an upward direction
when the wing descends, the upward
bending of the elastic feathers contrib-
uting to the horizontal travel of the
body of the bird.
out. The artificial wings which he made
of late differ from those recommended
by Borelli and others in the mode of
construction, in the manner in which
they are applied to the air, in the nature
of the power employed, and in the
opinion of the necessity for adapting
certain elastic substances to the root of
the wing if in one piece, and to the root
and the body of the wing if in several
pieces.
He maintains that no part of the wing
should be rigid; that, if the wing be in
one piece, it should be made to vibrate
obliquely and more or less horizontally,
so as to twist and untwist and make
figure-of-8 curves during its action, thus
enabling it to seize and let go the air
with wonderful rapidity, and in such a
manner as to avoid dead points; that
the entire wing must be under thorough
control during a cycle of motion, and
that steam, varying in intensity at every
stage of the down and up-strokes, pro-
duced by a direct piston action, is the
proper motive power; and that the root
of artificial wings must be supplied with
elastic structures in imitation of the
muscles and elastic ligaments of flying
animals.
The propounder of what has here been
so very briefly referred to has not only
the highest faith in his being the true
method, by pointing to an early consum-
mation of his plans, but ably and scien-
tifically enters into the merits and
These arguments appear so plausible minutiae of his every assertion. His
as to be acceptable to the superficial
reader, and even to the philosophers of
the past two centuries they have seemed
correct in general. Many have changed
his plans in detail and proclaimed their
new discoveries to the world without
giving Borelli credit for the same, and
up to this date they have stood firm.
The best proof of their invalidity lies in
the unfortunate circumstance that they
have never succeeded when applied to
practice.
Prof. Owen, Macgillivray, Bishop,
Liais and others, have added the word
backwards to Borelli's downwards.
Bell-Pettigrew was the first to differ
from Borelli and his votaries. He
proves that the action of the wing is not
downwards and backwards, but down-
wards and forwards, and that the other
arguments stated are fallacious through-
views are sustained by many eminent
authorities, who predict its practical
success; and we truly believe that the
inventor's only chance in this direction
is to study Bell-Pettigrew's propositions,
ponder them over critically and make
them the basis of his speculations and
work.
But it must not be imagined that
ballooning and aerial animal locomotion
are the only foundations upon which
both profound philosophers and hair-
brained visionaries have built their plans
and experiments.
Attempts have been made to harness
trained eagles to balloons and other ap-
paratus, and for a long time this possible
solution of the question was agitated
with fervor and enthusiasm. That this
is not the ultimately correct solution is
proved by the readiness with which it
446
VAN NOSTRAND'S ENGINEERING MAGAZINE.
was suffered to drop out of notice.
A blunt, but well-meaning, individual in a
technological journal lately remarked
that if humanity couldn't produce any
better than animal power to settle its en-
gineering difficulties, it had better re-
sume the furs and bone spears of its bar-
barous ancestry and give up civilization
as a bad job. And we cannot help feel-
ing as he does.
Of course, electricity has been sug-
gested. We noticed a communication
from an Australian in the New York
Herald lately, who had a plan of aerial
navigation on electric principles, and
only wanted some cash to show the world
that his principles could be carried into
successful execution. Electricity, some-
how or other, can do anything ; it is one
of these grand, mysterious institutions
that will be the future foundation of not
only engineering, but of everything.
Verne runs and lights his " Nautilus *'
with it, and this Australian is going to
aero-Nautilus it on the same plan. Peo-
ple expect great things from electricity,
especially since we can hear the grass
grow in Philadelphia with it from New
York, and perform other startling feats.
Peorile look knowing and hint at future
immensities of achievement ; the un-
known is always what people know most
about ; ask an average man to extract a
square root, to solve an equation of the
second degree, or to perform some similar
elementary operation, and he'll scratch
his head and tell you that he isn't up in
that sort of thing; but ask that same
man about the future electricity and it is
wonderful how much he knows about it,
while the sages of all ages and parts of
the globe are devoting their life-times to
the study of its nature, and finally de-
clare that they don't know anything
about it. Ask a professor of mathemat-
ics what force is. He don't know. Ask
a precocious student. Oh, he knows, and
he'll tell you all about it; dealing in argu-
ments and with propositions which are too
profound for anybody to understand.
We cannot be too "emphatic in warning
the precocious inventor against attempt-
ing to overreach science. Experience
has taught us that it leads to nothing.
We do not mean to say that speculation
should be abandoned, but we do not be-
lieve in building on a foundation which
cannot be supported.
Bell-Pettegrew has given us a founda-
tion which will stand. Build on that.
Experiment on electricity if you will,
don't build on deductions before a criti-
cal, scientific community has given them
the stamp of validity.
TRANSMISSION OF POWER BY COMPRESSED AIR.
By ROBERT ZAHNER, M. E.
Contributed to Van Nostrand's Magazine.
I.
HISTORICAL NOTICE.
The application of compressed air to
industrial purposes dates from the close
of the last century. Long before this,
indeed, we find isolated attempts made
to apply it in a variety of ways; but its
final success must be ascribed to the
present age — the age of mechanic arts —
an age inaugurated in so splendid a man-
ner by the genius of Watt, and which
has been so wonderfully productive in
good to mankind.
Without going into any details as to
its history, we shall only name the Eng-
lish engineers, Cubitt and Brunell,
who, in 1851-4, first applied compressed
air in its statical application to the sink-
ing of bridge caissons, the Genoese Pro-
fessor, M. Collodon, who, in 1852, first
conceived and suggested the idea of em-
ploying it in the proposed tunneling of
the Alps; and, finally, the distinguished
French engineer, Lommeiller, who first
practically realized and applied Collo-
don's idea in the boring of the Mt. Cenis
Tunnel.
II.
ITS APPLICATIONS AND ITS FUTURE.
The applications of compressed air are
very numerous, its most important one
TRANSMISSION OF POWER BY COMPRESSED AIR.
447
being the transmission of power by its
means.
Custom has confined the term " trans-
mission of power " to snch devices as are
employed to convey power from one place
to another, without Including organized
machines through which it is directly ap-
plied to the performance of work.
Power is transmitted by means of
shafts, belts, friction-wheels, gearing,
wire-rope, and by water, steam and air.
There is nothing of equal importance
connected with mechanical engineering
in regard to which there exists a greater
diversity of opinion, or in which there is
a greater diversity of practice, than in
the means of transmitting power. Yet
in every case it may be assumed that
some particular plan is better than any
other, and that plan can be best determ-
ined by studying, first, the principles of
the different modes of transmission and
their adaptation, to the special conditions
that exist; and, secondly, precedents and
examples.
For transmitting power to great dis-
tances, shafts, belts, friction-wheels and
gearing are clearly out of the question.
The practical in compressibility and want
of elasticity of water, renders the hy-
draulic method unfit for transmitting
regularly a constant amount of power;
it can be used to advantage only where
motive power, acting continuously, is to
be accumulated and applied at intervals,
as for raising weights, operating punches,
compressive forging and other work of
an intermittent character, requiring a
great force acting through a small dis-
tance.
Whether steam, air or wire-rope is to
be made the means of transmitting power
from the prime-mover to the machine,
depends entirely upon the special condi-
tions of each case. In carrying steam to
great distances very importannt losses
occur from condensation in the pipes;
especially during cold weather. The
wear and tear of cables lessen the ad-
vantages of the telodynamic transmis-
sion; steep inclinations and frequent
changes of direction of the line of trans-
mission often exclude its adoption; while
it is entirely excluded when it is rather
a question of distributing a small force
over a large number of points than of
concentrating a large force at one or two
points.
Compressed air is the only general
mode of transmitting power; the only
one that is always and in every case pos-
sible, no malter how great the distance
nor how the power is to be distributed
and applied. No doubt as a means of
utilizing distant, yet hitherto unavailable
sources of power, the importance of this
medium can hardly be overestimated.
But compressed air is also a storer of
power, for we can accumulate any de-
sired pressure in a reservoir situated at
any distance from the source, and draw
upon this store of energy at any time;
which is not possible either in the case
of steam, water or wire-rope.
Larger supply-pipes are required for
steam or water transmission; the incon-
veniences resulting from hot steam pipes,
the leakages in water pipes, the high ve-
locities required in telodynamic trans-
mission ar,e all without their counter-
parts in compressed air transmission.
Compressed air is furthermore independ-
ent of differences of level between the
source of power and its points of appli-
cation, and is perfectly applicable no
matter how winding and broken the path
of transmission.
But especially is compressed air adapt-
ed to underground work. Steam is here
entirely excluded, for the confined char-
acter of the situation and the difficulty
of providing an adequate ventilation,
render its use impossible; compressed
air, besides being free from the objec-
tionable features of steam, possesses
properties that render its employment
conducive to coolness and purity in the
atmosphere into which it is exhausted.
The boring of such tunnels as the Mt.
Cenis and St. Gothard would have been
impossible without it. Its easy convey-
ance to any point of the underground
workings; its ready application at any
point; the improvement it produces in
the ventilating currents; the complete
absence of heat in the conducting pipes;
the ease with which it is distributed
when it is necessary to employ many
machines whose positions are daily
changing, such as hauling engines, coal-
cutting machines and portable rock-drills;
these, and many other advantages, when
contrasted with steam under like condi-
tions, give compressed a value which the
engineer will fully appreciate.
There is every reason to believe that
448
VAN NOSTKAND'S ENGINEERING MAGAZINE.
compressed air is to receive a still more
extensive application. The diminished
cost of motive power when generated on
a large scale, when compared with that
of a number of separate steam engines
and boilers distributed over manufactur-
ing districts, and the expense and danger
of maintaining an independent steam
power for each separate establishment
where power is used, are strong reasons
for generating and distributing com-
pressed air through mains and pipes laid
below the surface of streets in the same
way as gas and water are now supplied.
Especially in large cities would the
benefits of such a system be invaluable;
no more disastrous boiler explosions in
shops filled with hundreds of working
men and women; the danger of fire
greatly reduced; a corresponding reduc-
tion in insurance rates; an important
saving of space; cleanliness, convenience
and economy. We say economy ! For
there is no doubt that a permanently
located air-compressing plant, established
on a large scale, and designed on princi-
ples of true economy and not with refer-
ence to cheapnes of construction, would
supply power at a much less cost than is
supposed. Besides, there are many natu-
ral sources of power, as water power,
which could by this means be utilized,
and their immense stores of energy con-
veyed to the great centers of business
and manufacture.
As affording a means of dispensing
with animal power on our street rail-
roads, compressed air has been proposed
as the motor to drive our street cars. It
has already met with some success in this
direction, and, to-day, there are eminent
French, English and American engineers
at work upon this interesting problem.
The compressed air locomotives of M.
Ribourt, now in use at the St. Gothard
Tunnel, give very satisfactory results.
They are compact, neat and compara-
tively economical.
Compressed air is also applied in a va-
riety of other ways; in signaling, in pro-
pelling torpedo boats; in ventilating
large and confined spaces; in driving
machinery in confined shops; in sinking
bridge caissons. The pneumatic dis-
patch system, the air brake, the pneu-
matic elevator and hoist are further ex-
amples of its use.
CHAPTER I.
The Conditions Modifying Efficiency
in the Use of Compressed Aie.
I.
loss of eneegy.
What is at present required in the use
of compressed air is a considerable dim-
inution in the first cost of obtaining it
by really improving the compressor, and
a practical means of working it at a high
rate of expansion without the present
attendant losses. In the best machines
in use at the present day, the useful ef-
fect^ that is, the ratio of the work done
by the air to that done upon it, is very
small. The losses are chiefly due to the
following causes:
1. The compression of air develops
heat; and as the compressed air always
cools down to the temperature of the
surrounding atmosphere before it is
used, the mechanical equivalent of this
dissipated heat is work lost.
2. The heat of compression increases
the volume of the air, and hence it is
necessary to carry the air to a higher
pressure in the compressor in order that
we may finally have a given volume of
air at a given pressure, and at the tem-
perature of the surrounding atmosphere.
The work spent in affecting this excess
of pressure is work lost.
3. The great cold which results when
when air expands against a resistance,
forbids expansive working, which is
equivalent to saying, forbids the realiza-
tion of a high degree of efficiency in the
use of compressed air.
4. Friction of the air in the pipes,
leakage, dead spaces, the resistance of-
fered by the valves, insufficiency of
valve- area, for workmanship and slovenly
attendance, are all more or less serious
causes of loss of power.
The question now is, how can we get
rid of these losses and obtain a higher
efficiency ?
The first cause of loss of work, name-
ly, the heat developed by compression,
is entirely unavoidable. The whole of
the mechanical energy which the com-
pressor-piston spends upon the air is con-
verted into heat. This heat is dissipated
by conduction and radiation, and its me-
chanical equivalent is work lost. The
compressed air, having again reached
TRANSMISSION OF POWER BY COMPRESSED AIR.
449
thermal equilibrium with the surround-
ing atmosphere, expands and does work
in virtue of its intrinsic energy.
We proceed to the second loss, which
is the work done in driving the com-
pressor-piston against the increase of
pressure due to the heat of compression.
Since the temperature increases more
rapidly than it ought, according to
Boyle's 'law, the work necessary to com-
pression is greater than if the tempera-
ture were to remain constant.
The theoretical efficiency of the com-
pressing and working cylinders, as given
further on by eq. (486), is:
where T1 is the absolute temperature of
the air at its exit from the compressor,
and 60 the absolute temperature at its
entrance into the working cylinder, which
in practice is that of the surrounding
atmosphere. Hence we can increase the
value of this fraction only by decreasing
the denominator Ta, that is the final heat
of compression. This can only be done
by abstracting the heat during compres-
sion, or by using very low pressures.
But low pressures are excluded by other
considerations. The weight of air, w,
needed per second to perform a given
amount of work would have to be con-
siderably increased, and this would neces-
sitate larger pipes, larger cylinders, and
would result in a cumbrous and expen-
sive arrangement.
The only remaining alternative, there-
fore, is to bring about in the compressor
the cooling which the air now under-
goes after having left it. Table VII
shows respectively the portion of work
lost when the air is not cooled in the
compressor and that lost when it is com-
pletely cooled, and will make manifest
the advantage there is in cooling. For
a pressure of six atmospheres the work
spent in isothermal compression to that
spent in adiabatic compression is as 3 to
4; and this ratio decreases rapidly as the
pressure increases.
II.
METHODS OP COOLING.
There are three methods in which cold
water is applied to cool the air during
its compression:
1. In case of the so-called hydraulic
Vol. XIX.— No. 5—29
piston or plunger compressors, the air is
over and in contact with a column of
water which acts upon the air like an
ordinary piston, its surface rising and
falling with the backward and forward
motion of the plunger. It is obvious
that the cooling effect of this large mass
of water is very small. There is nothing
but surface contact, and water possesses
in a slight degree only, the property of
conducting, through its mass, heat re-
ceived on its surface. But we obtain all
the advantages there are in having the
air completely saturated with water-
vapor during its compression, as well as
all the disadvantages of having saturated
compressed air to work with. What has^
been here said of hydraulic plunger-
compressors, applies equally to hydraulic
or ram compressors (first used by Som-
meiller at Mt. Cenis, but now obsolete).
2. By flooding the external of the
cylinder, and sometimes also the piston
and piston-rod. This method of cooling
presents neither the advantages nor dis-
advantages incident to direct intercon-
tact between the air and water; it is that
generally adopted in American practice,
especially where it is necessary to expose
the air-pipes to the out-door atmosphere
of winter. The cooling which it effects
is, however, only an approach to that
which insures the highest efficiency.
3. By injecting into the compressor
cylinder a certain quantity of water in a
state of the finest possible division, i. e. in
the form of spray. This method of cooling
was first applied by Prof. Collodon in the
compressors used at the St. Gothard
Tunnel. It is by far the most rational,
complete and effective. In this fine state
of division the water has many more
points of contact with the air, which is
both completely cooled and kept thor-
oughly saturated during compression. It
is extremely important that the quantity
of water injected into the compressor
be a minimum, and hence the weight re-
quired for different tensions is given in
a table further on.
III.
CONDITIONS MOST FAVORABLE TO ECONOMY
IN THE USE OF COMPRESSED AIR.
By working air at full pressure we
avoid the formation of ice in the pipes
and exhaust ports, not so much because
the air is less cooled (for the great fall
450
VAN NOSTRAND'S ENGINEERING MAGAZINE.
of temperature produced by the sudden
expansion at the instant of exhaust is
almost equal to thlit produced by inte-
rior expansion), but because the air in
exhausting requires a high velocity, and
this opposes the deposit of ice crystals
by its purely mechanical effect, and by
the heat developed by its friction.
But even at full pressure we cannot
work with high tensions without serious
drawbacks. In England, several trials
were made at the Govan Iron Works and
other places to use air under tensions of
eight and nine atmospheres, but they
were forced to return to low pressures,
owing to the entire arrest of the ma-
chine from the formation of ice in the
ports. Hence, not taking into account
the fact that the useful effect decreases
as the pressure increases, we conclude
that it is not good practice, even at full
pressure, to work with a tension much
over four atmospheres^ unless we employ
special means to reheat the working air.
But while by working at full pressure
with moderate tensions, we avoid the in-
conveniences of very low temperatures,
the efficiency obtained is also very low.
Notwithstanding this, even up to the
present time air is almost exclusively
worked at fall pressure, especially in the
United States. This is because the great
cold produced by expansive working has
made its adoption impossible. With a
cut-off at i stroke the temperature of the
air falls 71° C, and at \ cut off 140° C.
Now, to avoid these low temperatures,
is is necessary either that the initial tem-
perature of the compressed air be raised
by heating it before its introduction into
the working cylinder, or that the cylin-
der in which it expands be heated, or
that the compressed air be supplied with
heat directly during its expansion by
means of the injection of hot water.
In 1860, M. Sommeiller, in order to
utilize expansion, heated his% working
cylinders at Bardonneche by means of a
current of hot air circulating around the
cylinders in small pipes. By this means
he was enabled to cut off at f stroke.
In 1863, M. Devillez recommended
that the cylinder be placed in a tank
through which hot water was to circu-
late. Other devices were to place the
cylinder into a tank of water, into which
from time to time fresh supplies of quick-
lime were to be thrown. Waste cotton,
soaked in petroleum, was also used to
heat the working cylinder.
Finally, in 1874, Mr. C. W. Siemens
proposed the injection of hot-water into
the compressed-air engine cylinder to
keep the temperature of the expanding
air from falling below the freezing point,
just as we inject cold water into the
compressor cylinder to prevent a great
rise of temperature during compression.
This is by far the most efficient mode of
supplying heat to the expanding air. Ex-
pansion is made completely practicable,
and hence the efficiency of the engine is
greatly increased, as was shown by M.
Cornet, who was the first to apply Mr.
Siemens' plan and to prove conclusively
its great practical utility.
The quantities of hot water to be in-
jected into the cylinder should always be
a minimum; they are given in a table
further on.
IV.
EFFICIENCY ATTAINED IN PRACTICE.
It is desirable to know what efficiencies
have been attained in practice — of com-
pressors, of compressed-air engines, and
of the two machines together as a
system.
1. By efficiency of compressor is meant
the ratio of the effective work spent upon
the air in the compressor to that de-
veloped by the steam in the driving en-
gine; or if you choose the resistance di-
vided by the power.
a. In compressors without piston or
plunger, such as the hydraulic com-
pressor of Sommeiller, the efficiency is
always less than .50. These machines
are interesting on account of their sim-
plicity, but their useful effect is always
very small.
b. In the so-called hydraulic piston,
or plunger-compressor, an efficiency of
.90 has been obtained when working at a
low piston-speed to pressures of four and
five atmospheres.
c. The compressors of Albert Schacht
at Saarbriicken, in which the cooling is
wholly external, have shown an efficiency
of .80 when compressing to a tension of
4 effective atmospheres.
d. Prof. Collodon's compressors, into
which water is injected in the form of
spray, and which were run at a piston-
speed of 345 feet, and compressed the
air to an absolute tension of 8 atmos-
TE ADMISSION OF POWER BY COMPEESSED»AIE.
451
*?■- 49^
•49w
W; the actual work done by the air,
W
then the real efficiency will be ^ .
Now in the ordinary conditions of
practice we know that TV\ is at best .70
W, and W is only about .70 W2; hence
W
E'=real efficiency ==-_
TY6" =.49E.
w
The value of ^-2 (=E=the theoretical
efficiency) is .55 for full pressure and
.75 for complete expansion. Hence, sub-
stituting these values of E above, we
find for these two cases a final efficiency
of .27 and .37.
VI.
LOSSES OF TRANSMISSION.
The losses due to transmission are cal-
culated further on.
At the works for excavating the Mt.
Cenis Tunnel the supply of compressed
air was conveyed in cast iron pipes 7f
inches in diameter. The loss of pressure
and leakage of air, from the supply pipes,
in a length of one mile and -fifteen yards,
was only 3h$ of the head; the absolute
initial pressure was 5.70 atmospheres
| and it was reduced to 5.50 atmospheres,
whilst there was an expenditure at the
At the Blanzy mines, M. Graillot has ! rate of 64 cubic feet of compressed air
found for a final efficiency, .22 to .32 of I per minute. In the middle of the tun-
the effective work of the steam. nel, through a length of pipe of 3.8 miles,
M. Ribourt, by experimenting on the the absolute pressure fell only from six
new compressed-air locomotives built i atmospheres to 5.7 atmospheres, or to .95
for the St. Gothard Tunnel, found that ! of the original pressure.
the ratio of the tractive effort developed At the Hoosac Tunnel the air was ear-
to the original power, (in this case a j ried through an 8-inch pipe from the
head of water), was .23; that is, after I compressors to the heading, a distance of
pheres, gave an efficiency which never
descended below .80, while the tempera-
ture of the air never rose higher than 12
to 15 degrees C.
2. The efficiency of compressed-air
engines is the ratio of the work which
they actually do to that which is theo-
retically obtainable from the compressed
air. The following are examples of its
value as found by experiment:
At the Haigh Colliery, Eng., .70
" " Ryhope " " .66
M. Ribourt has found for his locomotives
.50 to .60.
In general it may be said that in the
very best machines we can count upon
from .70 to .75; while in the ordinary
ones, working against a variable resist-
ance, this efficiency descends to .50 and
.55.
3. The efficiency of the whole system
together, that is, the ratio of the work
measured on the crank-shaft of the com-
pressed-air engine, to that done by the
prime mover, is found to be about .20 to
.25 high pressures, and from .35 to .40
for low pressures.
Experiments made at Leeds show a
net efficiency of .255 when working with
2.75 effective atmospheres pressure,
and .455 when with 1.33 effective atmos-
pheres pressure.
passing the turbine, the compressor, the
expansion regulator, and the cylinders of
the locomotive, there remained .23 of
the original power.
THE EFFICIENCY OF FULL PRESSURE AND
OF EXPANSION COMPARED.
Let W, be the work spent upon the air
in the compressor:
W2 the" work which the compressed air
is theoretically able to do ; then its the-
W
oretical efficiency will be ™2.
If W=the actual work done by the
prime mover, and
7,150 feet, operating six drills, with an
average loss of two pounds pressure.
CHAPTER II.
The Physical Properties and Laws
of Air.
I.
INTRODUCTORY.
A fluid is a body incapable of resisting
a change of shape. Fluids are either
liquids, vapors or gases. Water may be
taken as the type of the first; steam is
the type of all vapors, and air of all
gases.
Gases are either coercible gases, i. e.,
452
VA*N NOSTKAND'S ENGINEERING MAGAZINE.
such as under ordinary circumstances
may be condensed into liquids or even
solids, as C02; or permanent gases, which
retain their aeriform state under all ordi-
nary circumstances of temperature and
pressure. This distinction is convenient.
Air has been condensed, but certainly
not under ordinary circumstances.
Air then is a permanent gas, ancT may
be considered a perfect fluid ; that is,
1. It is incapable of experiencing a
distorting or tangential stress, its mole-
cules offering no resistance to relative
displacement among themselves; hence
no internal work of displacement need
be considered.
2. It has the power of indefinite expan-
sion so as to fill any vessel of whatever
shape or size.
3. It exerts an equal pressure upon
every point of the walls of the vessel
enclosing it.
4. It is of the same density at every
point of the space it occupies.
II.
boyle's law.
This law states that the temperature
being constant, the volume of a gas va-
ries inversely as the pressure, &c, for-
mulated,
pv'=p0v0 (1)
Where v0=the volume of a given
weight of the gas at freezing tempera-
ture and a pressure pn; and ?/ = the vol-
ume of the same weight of gas at the
same temperature and at any pressure jt?.
Dry air, a mechanical mixture of
oxygen and nitrogen, being a permament
gas, obeys this law.
III.
THE LAW OF GAY-LUSSAC.
This second law of gases may be
stated thus: The volume of a gas under
constant pressure expands when raised
from the freezing to the boiling temper-
ature, by the same fraction of itself,
whatever be the nature of the gas form-
ulated:
v = vl(l + a1t) (2)
It has been found by the careful
experiments of M. M. Rudberg, Reg-
nault and Prof. Balfour Stewart and
others, that the volume of air at constant
pressure expands from 1 to 1.3665 be-
tween 0° C. and 100° 0. Hence for a
variation in temperature of 1° C, the
volume varies by .003665 or -^-g- of the
volume which the air occupied at 0° C.
and under the assumed constant pressure.
In equation (2) the coefficient a, is there-
fore equal to
JL
v 6 '
IV.
Combining the equation formulating
Boyle's law with that formulating Gay-
Lussac's, we obtain.
Pv=p0v0{l+a1t)=p0v0al{-- + t);
a1
or letting a=— =273, we have
pV =?& (a + 1) =fe {a + *) (3)
This last equation is a general expres-
sion for both Boyle's and Gay-Lussac's
law, and completely expresses the rela-
tion between temperature volume and
pressure.
R is a constant and depends upon the
density of the gas. Its value for at-
mospheric air is determined as follows:
The weight of the standard unit of
volume of a substance in any condition
is the specific weight of that substance in
that condition.
The specific weight of air, that is to
say, the weight of a cubic foot of air at
0°C. and under a pressure of 29.92 inches
of mercury, is according to M. Regnault
.080728 lbs. avoirdupois.
The specific volume of a gas is the vol-
ume of unit of weight; it is the recipro-
cal of the specific weight.
The specific volume of air, i.e., the vol-
ume in cubic feet of one pound avoirdu-
pois at 0° C. and under the pressure of
29.92 inches mercury is:
vn= — - =12.387 cubic feet. '
0 .080728
Let j»Q = 2116.4, the mean atmospheric
pressure in lbs. per square foot. Then
R=?A
2116.4X12.387
273
V.
= 96.0376.
ABSOLUTE TEMPERATURE.
Making £= — 273 in the equation
pv = H(a + ft
TRANSMISSION OF POWER BY COMPRESSED AIR.
453
the second member reduces to zero, and
hence
pv=o.
The distance of the freezing point
from the bottom of the tube of an air
thermometer is to the distance of the
boiling point from the bottom as 1:1,3665.
Hence, in the centigrade scale, where
the freezing point is marked 0° and the
boiling point 100°, the bottom of the
tube will be marked— 2 72°.85. The
lowest reading of the scale is, therefore,
— 273°. If this reading could be ob-
served it would imply that the volume
of the air had been reduced to nothing.
This is evidently a purely theoretical
conception, but in dealing with questions
relating to gases it is exceedingly con-
venient to reckon temperatures, not from
the freezing point but from the bottom
of the tube of an airthermometer. Ab-
solute zero, therefore, is marked — 273° on
the Centrigrade scale (corresponding to
— 459.°4 on the Fahranheit's scale) and
is the temperature at which all molecular
motions cease, and the mechanical effect,
which we call pressure, and which is due
to these motions, becomes zero.
VI.
LAW OF THE PRESSURE, DENSITY AND
TEMPERATURE.
Let D0=the density of a weight w of
air at the temperature 0° C. and under |
the pressure poi v0 being the correspond-
ing volume;
D=its density at pressure p, tempera-
ture t, v being its corresponding volume;
D'=its density at temperature 0° C. |
pressure p and volume V.
We shall have
That is, the density of a gas is inversely
as its temperature, the latter being rec-
oned from absolute zero.
Combining equations (4) and (o),
Dp a
-J9xo7rt>ov
D
a + t
P=%? X D.
But D=— , and hence
(a + t)
(6)
(6a)
(6) shows that the density of a gas is:
At constant temperature, directly as
the pressure;
At constant pressure, inversely as the
absolute temperature.
P
yr = constant for any given gas. For
V 2116.4
air V0 = ^80728 = 26216'43 (according
to Rankine, 26214); this is the height in
feet of a column of fluid of density D0,
which produces a pressure £>0 pounds per
square foot of surface; letting H be this
height, the weight of the column having
one square foot for its surface will be
D.H, or
D.H=J>0.
If in (6a) we make v=l, we get
P
p J_
a + t X P0~aXt XR
or by taking w= unity,
»-*.
and v=
D
Placing this value of v in equation (1)
we get
p. iv w
that is, the pressure of a gas is propor-
tional to its density.
From (2) we have,
D' \+a't~a + f {0)
which is the weight of unit of volume,
or the specific weight of air.
Making w=l in same equation, we
have for the volume of unit of weight,
p0 a + t a+t
V*<* P P
(8)
called the specific volume. (7) and (8)
are rciprocals of. v each other.
VII.
THE MEASUREMENT OF HEAT.
Any effect of heat may be used as a
means of measuring it, and the quantity
of heat required to produce a particular
effect is called a thermal unit. It has
been found best to take a thermal unit to
be the quantity of heat which corre-
sponds to some definite interval of tem-
perature in a definite weight of a
particular substance.
454
VAN nostrand's engineering magazine.
Def. A British Thermal Unit is the
quantity of heat which corresponds to an
interval of one degree of Fahrenheit's
scale, in the temperature of one pound
of pure liquid water at its temperature
of greatest density (39° 1 Fahr).
Def A Calorie, or French Thermal
Unit, is the quantity of heat which
corresponds to the Centigrade degree in
the temperature of one kilogram of pure
liquid water, at its temperature of great-
est density, (3° 94 C).
Def. The Specific Heat of a body, is
the ratio of the quantity of heat required
to raise that body one degree, to the
quantity required to raise an equal
weight of water one degree.
It has been proven for permanent
gases, that,
1. The specific heat is constant for
any given gas, and is independent of the
temperature and pressure ;
2. The thermal capacity per unit of
volume, is the same for all simple gases
when at the same pressure and tempera-
ture ;
3. The specific heat increases with the
temperature, and probably with the
pressure, when the gas is brought near
the point of liquifaction, and no longer
obeys Boyle's law.
The above three conclusions are true
of specific heat at constant volume, as
well as of specific heat at constant press-
ure, as far as regards simple gases and
air, (which, being a mechanical mixture,
obeys the same laws as simple gas).
It was shown by Laplace, that the
specific heat of a gas is different, accord-
ing as it is maintained at a constant
volume, or at a constant pressure, during
the operation of changing its tempera-
ture.
The specific heat of gases was inde-
pendently determined by M. Regnault
and Prof. Rankine; experimentally by
the former, and theoretically by the
latter. Their results agreed exactly,
and are those now generally accepted.
As given in Watt's Dictionary of Chem-
istry,
The specific heat at constant pressure
is .238
As we shall find farther on, the specif-
ic heat at constant volume is .169.
.238
.169
= 1.40 = r
CHAPTER III.
Thermodynamic Principles and For-
mulas.
I
INTRODUCTORY.
It is well known that the cylinder of
an air compressor becomes very hot even
at a low piston- speed. This fact brings
us face to face with the doctrine of the
conversion of energy; for it is the con-
version of the visible, mechanical energy
of the piston into that other invisible
form of energy called heat. Thus we
see we are at the very outset confronted
with a thermal phenomenon, whose con-
sideration involves the science called
thermodynamics. To begin with we
had no other but the visible mechanical
energy of a moving piston; but very
soon sensible heat manifests itself, and
this heat can be developed only at the
expense of part at least, of the energy of
the moving piston.
These phenomena are referable to the
two general principles which form the
basis of the science of thermodynamics,
viz :
1. All forms of energy are convertible.
2. The total energy of a substance or
system cannot be altered by the mutual
actions of its parts.
* "The conversion of one form of
energy into another takes place with as
great certainty and absence of waste,
and with the same integrity of the ele-
mentary magnitude as the more formal
conversion of foot-pounds in kilogram-
meters." "In the development of the
axioms that nothing is by natural means
creatable from nothing, and that things
are equal to the same thing only which
are equal to each other, and in the appli-
cation to them of empirical laws with
reference to the behavior of bodies under
the action of heat and mechanical effect"
consists chiefly the science of thermody-
namics.
The general equation of thermody-
mamics which expresses the relation be-
tween heat and mechanical energy under
all circumstances, was arrived at inde-
pendently in 1849 by Professors Clau-
sius and Rankine. The consequences of
* " History of Dymamical Theory of Heat," by the
late Porter Poinier, M.E., in Popular Science Monthly
for January, 1878.
TRANSMISSION OF POWER BY COMPRESSED AIR.
455
that equation have since been developed
and applied by many distinguished
writers.
Of course we shall here confine our-
selves to so much only of the M echanical
Theory of Heat as is necessary to an in-
telligent comprehension of our subject
in doing so, and shall follow in outline
the treatment given by M. Pochet, in his
admirable "Nbicvelle Mechanique Indus-
trielle" making free use, at the same
time, of the works or Zeuner, Rankine
and Clausius.
II.
HEAT AND TEMPERATURE.
Heat denotes a motion of particles on
a small scale just as the rushing together
of a stone and the earth denotes a mo-
tion on a large scale, a mass motion. It
is due to a vibratory motion impressed
upon the molecules of a body. The
more rapid the vibrations the more in-
tense the heat. The quantity of heat in
a substance could be measured by multi-
plying the kinetic energy of agitation of
a single molecule by the number of mole-
cules in unity of weight, supposing the
substance to be homogeneous and the
heat uniformly distributed. Thus the
thermometer and dynamometer reveal to
us phenomena which are in reality ident-
ical, and we can establish a measuring
unit to which both effects can be referred.
Temperature is the property of a body
considered with reference to its power of
heating other bodies. It is a function of
the variables, volume and pressure, or,
that is, all bodies having the same press-
ure and volume have the same tempera-
ture. This is expressed by the differen-
tial equation:
where (y ) and (y ) are the partial dif-
ferential co-efficients, dt in the former de-
noting the increment of t when, v re-
maining constant, p alone is increased by
dp ; and in the latter, the increment re*
ceived by t when p remaining constant,
v is increased by dv ; whilst in the first
number of the equation, dt represents
the total increment of t due to the simul-
taneous reception by p and v of the in-
crements dp and dv, respectively.
III.
THE TWO LAWS OF THERMODYNAMICS.
The whole mechanical theory of heat,
rests on two fundamental theories: *
1. That of the equivalence of heat and
work; whensoever a body changes its
state in producing exterior work, (posi-
tive or negative), there is an absorption
or disengagement of heat in the propor-
tion of one British thermal unit for every
772 foot pounds of work, (or of one
French thermal unit for every 423.55
kilogrammeters of work).
This mechanical equivalent of heat
was first exactly determined by Mr.
Joule, in honor of whom it is called
Joule's equivalent, and is denoted by the
symbol J.
2. The theorem of the equivalence of
transformations; when a body is success-
ively put in communication with two
sources of heat, one at a higher tempera-
ture t, the other at a lower temperature
t0, its temperature remaining constant
and equal to that of each source during
the whole time of contact, and the body
neither receiving nor losing heat except
by reason of its contact with the two
sources, the ratio of the quantity of heat
Q given out by the higher source to the
quantity Q1 transferred to the lower
source, is independent of the nature of
the bodies; it depends only on the
temperatures, t and t0, of the two sources.
Clausius states this as follows: In all
cases where a quantity of heat is con-
verted into work, and where the body
effecting this transformation ultimately
returns to its original condition, another
quantity of heat must necessarily be
transferred from a warmer to a colder
body; and the magnitude of the last
quantity of heat, in relation to the first,
depends only on the temperature of the
bodies between which heat passes, and
not upon the nature of the body effecting
this transformation; or, more briefly,
heat cannot of itself pass from a colder
to a warmer body.
IV.
HEAT AND MECHANICAL ENERGY.
The quantity of heat which must be
imparted to a body during its passage,
in a given manner, from one condition to
another, (any heat withdrawn from the
* See Clausius on Heat, Memoir.
456
VAN NOSTRAND'S ENGINEERING MAGAZINE.
body being counted an important nega-
tive quantity) may be divided into three
parts, viz :
1. That employed in increasing the
heat actually existing in the body;
2. That employed in producing in-
terior work.
3. That employed in producing ex-
terior work.
The first and second parts, called re-
spectively the thermal and ergo7ial con-
tent* of the body, are independent of
the path pursued in the passage of the
body from one state to another; hence
both parts may be represented by one
function, which we know to be com-
pletely determined by the initial and
final states of the body. The third part,
the equivalent of exterior work, can only
be determined when the precise manner
in which the changes of condition took
place is known.
Let JQ=the element of heat absorbed
during an infinitesimal change of con-
dition ;
Uo = the free heat present in the body
at the beginning, i.e., the body's intrinsic
energy;
11= the free heat present in the body
at the end of the change, plus the heat
consumed by internal work during the
change of state;
pdv will be the work accompanying
the passage of the body from a state
(pxv) to a state (p + dp, v + dv) ;
Then the heat spent while the body
passes from one temperature t to another
t + dt, and from one state (pxv^) to an-
other (p + dp, v + dv) will be :
dQ=(U-UQ) + 1rpdv,
=dU+j.pdv
(10)
where du depends upon the initial and
final circumstances, while -=-.pdv depends
J
on the intermediate circumstances of the
change of state.
We can write dii=o and entirely ex-
clude interior work and heat by confining
ourselves to cyclical processes, that is to
say, to operations in which the modifica-
tions which the body undergoes are so
arranged that the body finally returns
* Clausius on Heat. Memoir.
exactly to its original condition, the inte-
rior work, positive and negative, exactly
neutralizing each other.
u=f (p, v),
that is, the internal heat of a body de-
pends only upon the volume of the body,
and the pressure to which it is subjected.
Hence the increase of internal heat when
the body passes from a state (p9 v) to a
state {p + dp, v + dv) will be :
du
SMS* <»>
*=©*+. {(SKI* o?
Substituting in equation (10) the value
of du as given by equation (11), we have
an equation which is not integrable;
since this would require that the second
derivatives of the co-efficients of dp and
dv (which are, respectively, =— -, and
-rz — =- + J) should be equal to each
dv.dp
other*; this would imply the impossible
condition J=o. That is, mechanically
speaking, the quantity of heat passing
cannot be expressed as a function of the
initial values of p and v. The equation
can only be integrated when we have a
relation given, by means of which t may
be expressed as a function of v, and
therefore p as a fnnction of v alone. It
is this relation which defines the manner
in which the changes of condition take
place; the quantity of heat passing de-
pends upon the intermediate circum-
stauces of change of state, circumstances
which may be anything.
When a body is heated from a tem-
perature t to another t-\-dt, preserving
the same volume, no external work will
be done and dv = o. Hence eq. (12) will
become:
= CX dt (13)
which, by definition, is the specific heat
at constant volume.
The above equation gives:
du I dt\ .n ,
* See Ray's Infinitesimal Calculus, p. 366 ; also McCul-
lough. on Heat, arts. 61 and 62.
TRANSMISSION OF POWER BY COMPRESSED AIR.
457
the partial differential co-efficient of t
with respect to p.
If the body passes from t to t + dt
under constant pressure, dp>=o, and hence
(12) becomes:
*H ©+#*=•* (14)
which, by definition, is the specific heat
at constant pressure.
From (14) we have:
Substituting these values of the partial
derivatives in eq. (12), we obtain a sec-
ond expression for dQ, viz. :
It is convenient to have this equation
in a form involving only the temperature
and specific heats, and not the quantity
Q. We obtain such a form by differen-
tiating (13a) with respect to v, and (14a)
with respect to p and subtracting the
first result from the second. The form
obtained is:
/~\dv)\dp)
(16)
\=(o
dH ldc\ldt
dv.dp \dp)\dv
V.-
THE DIFFERENTIAL EQUATION OF THE
SECOND PRINCIPLE.
In the figure,
1. Let OA=the initial volume of a
body whose temperature is t • it expands
in contact with a source of heat, (isother-
mally), from volume OA to volume OB,
when its temperature is then still t.
Q=the quantity of heat supplied by
the source;
2. It is now left to expand adiabati-
cally, i.e., without the addition or sub-
traction of heat, from volume OB to
volume OC, when its temperature will
have fallen to t0;
3. Now place it in contact with a
source of heat of the same temperature
t0, and compress it from OC to OD,
when its temperature is still t0.
Qx=the quantity of heat that has
passed into the source;
4. Compress it adiabatically from
volume OD to volume OA, when its
temperature will again be t; the body
has now undergone a complete cycle,
during which it has evidently done work
represented the area abed ; hence,
Q— Q1=heat disappeared, and from
the first law of thermodynamics,
Q-Q,=j
X abed-
1
XA.
(17)
Now the second law of thermodynam-
ics states that Q and Q1, (the heat
received and the heat given out), are
independent of the nature of the bodies,
and dependent only upon the tempera-
ture.
Suppose that the difference of temper-
ature of the two sources of heat is
infinitely small, t and t-\-dt. Also
consider t and v as the independent vari-
ables determining the state of the body,
p=f(v,t). ' . . , .
A, in the above equation, is the in-
tegral between v0 and v of the elementary
areas, such as ef. Now if ~Ee=p, E/is
what p will become when the volume
remains constant, and the temperature
takes an increment dt ; fe therefore
measures the differential increment
(th
dp
where ^y^the partial derivative of p
at
with respect to t.
Hence, Q-Q-A^i/^f )«»
taking the independent variable dt out
of the integration symbol.
Q is the heat supplied to^keep at t the
458
VAN nostrand's engineering magazine.
temperature of the body expanding
from v0 to v, and, therefore,
Q=p(tio0,v ; the nature of the bodies);
also,
Q'=F"{t, v„ v)=¥ (t),
the variables v0, v being implicitly con-
tained in F.
Since Q=Q' when t becomes t + dt we
have,
and
Q=F(t + dt)=F(t) + F'(t) dt
According to the second principle,
Q ,»•
Q
7 is independent of the nature of the
bodies; hence,
and
c?y
1 F (t) f» (dp\
Now, suppose v — v0 becomes indefinite-
ly small and equal to dv; Q7 will become
dQ, Q being the heat necessary to keep
at t the temperature of a body whose
volume increases by dv; hence the dif-
ferential equation of the first order,
dQ=-L p (t) -£ dv (18)
the differential equation of the second
principle.*
' Calculation of the function p (t). It
may have several forms. Making dt=o
in eq. (9), we get,
/dt\
\dv/ 7
W\ ;
\dp)
Placing this value of dp in eq. (15),
dQ=(c-Cl) [^ dv.
Moreover in (9) \4-) represents the
partial derivative of p with relation to t
when v is constant; making dv = oy
* See Zeuner, "Theorie Mechanique de la Chaleur,"
troisierne section, iii.
Also, Clausius oh Heat, first Memoir.
Idp\ _
\dt I ~
IdtV
\dp/
Hence eq. (18) may be written,
W
<djL
Equating this with the value of dQ
above, we have,
from which p (t) may be calculated.
Again, if we take Eq. (16) and sup-
pose it applied to bodies whose specific
heats c and c, are independent, the first
of the pressure and the second of the
volume, as is the case in permanent
gases, these conditions give \-f-j and
( -j j equal to zero, and the equation be-
comes,
( - \IJlL\-\
{c GAdpdv.)~r
Dividing eq. (19) by this we get,
(dt_\(dt\
\dv/\dv/
p{t)
<dpl\dv>
cVt
dp dv
(20)
(21;
giving p (t) as a function of t [=/
C?V)] an(^ of lts partial derivatives.
Mr. Arnold Hague, the eminent
American geologist, has been engaged
by the Chinese Government to examine
and report upon the mineral resources
and mining industry of the Celestial
Empire, and sailed from San Francisco
on Thursday, the 15th of August, by the
steamer Gaelic, to enter upon his duties.
He expects to take the field immediately
upon arrival, and continue active opera-
tions until about the first of December,
when he will go into winter quarters.
The excellent work performed by Mr.
Hague in connection with King's Survey
of the Fortieth Parallel, and more re-
recently in Guatemala, is a guarantee of
his fidelity and skill in this new under-
taking.
ADVANCES IN THE MANUFACTURE OF IRON AND STEEL.
459
RECENT ADVANCES IN THE MANUFACTURE OF IRON AND
STEEL, AS ILLUSTRATED IN THE PARIS EXHIBITION.*
By RICHAED AKEEMAN, Professor at the School of Mines, Stockholm.
From "The Engineer."
As international exhibitions have of
late followed so close on each other, it is
natural that the discoveries and inven-
tions that can be made in the interval
between each and its successor are not
numerous. The technical literature too,
especially that which is concerned with
the manufacture of iron and steel, has in
the last fifteen years been so developed
that nearly all improvements are, early
after their introduction, found described
in a number of periodicals. This has
been conspicuously the case since the
foundation of the Iron and Steel Insti-
tute, which I now have the honor of ad-
dressing, and which has been beneficial
in so high a degree to that branch of
metallurgy to which its attention is more
particularly devoted; for at its meetings,
as is well known, the most pressing ques-
tions affecting the production of iron and
steel have been discussed with eminent
practical knowledge from every point of
view, and many facts highly interesting
to the manufacturer, and of which, with-
out intervention of this excellent associ-
ation, mankind would at most have had
but a faint idea, have been, thanks to
your " Transactions," disseminated over
the whole world. In this connection I
must also ask to be allowed to point out
another advantage which this association
has brought about. Ten years ago there
still prevailed at many iron and steel
works a very great reluctance to open
their doors to strangers, and many an
establishment which now willingly ad-
mits strangers was then, if not altogether,
shut, at least not accessible in the same
degree as now. Who can well deny that
the opinions expressed by the Institute
conducted in a very great degree to
bring about this change ? And, further,
that the facilitated access to iron and
steel works has greatly promoted a gen-
eral knowledge of the latest advances
and improvements? A certain result,
however, of all this is, that an iron met-
allurgist, who has properly kept pace
* Iron and Steel Institute.
with the times, can now scarcely expect
that an International Exhibition can pro-
duce anything altogether new to him
within its walls. Neither for this reason
ought it to be required of me, that I
should have something new to say to you,
even with all the resources of that on the
Champs de Mars behind me. Indeed, I
would never have entertained the ques-
tion of making a demand on your precious
time, as I now do, if I had not been
asked to do so by certain prominent men
within this society.
As the leading principle pervading the
whole of modern iron manufacture, it
must in the first place be pointed out
how the cinder-free ingot, iron and steel,
is always more and more supplanting the
old cinder-mixed wrought iron. This
change, as is well known, derives its real
origin from the time of Mr. Bessemer's
grand invention, which marks an epoch
in the history of the iron trade. This
important change in the process has also
been powerfully assisted by the diminu-
tion in the cost of fusing iron and steelj
which has been placed within reach by
the important application of the so-called
regenerative principle by our honored
president, Dr. Siemens. For, as we all
know, it is not enough that crucible steel
can by means of this furnace be made
more cheaply, but the Siemens furnace
itself has also realised the long-cherished
hope of being able, without the help of
the costly crucible, to melt steel and iron.
Open hearth metal may be said to have
celebrated its baptismal ceremony just at
the last Paris Exhibition, when it was
named, after its first maker, Martin
metal. The Bessemer manufacture,
though then ten years old, may be said
to have been at the same time in its
childhood ; and though much railway
material of Bessemer metal was shown
at that Exhibition, the opinion of its
goodness was yet so little established
that there were works which, under the
common appellation cast steel, sought to
conceal that their products were manu-
factured by the Bessemer process.
460
VAN NOSTKAND's ENGINE EKING MAGAZINE.
How different is the aspect of affairs
to-day, after an interval of only eleven
years ! Although many a Bessemer works
now employs materials inferior to those
then used, none seeks any longer to con-
ceal its Bes.semer manufacture, but with
pride exhibits its Bessemer rails, which,
as is well known, are now in process of
completely supplanting rails of puddled
iron; and one can form some idea of the
completeness of the arrangements for
rolling Bessemer rails by inspecting the
rails from Seraing, 55 metres in length;
from Charles Cammell and Co.'s, 43
metres; and Brown, Bay ley, and Dixon's
rails, 130 feet long, rolled direct from the
ingot without intermediate heating.
Sweden had, indeed, already, at the Paris
Exhibition of 1867, shown the finest
razors and other similar wares of Bes-
semer metal, and in the manufacture of
cutlery in Sweden this material is now
almost exclusively employed. Styria
had likewise then to offer beautiful work
of embossed Bessemer metal; but these
cases formed at that time rare excep-
tions, depending on the special goodness
of the ores which were employed in the
Bessemer manufacture of those countries.
For some time Bessemer metal was al-
most exclusively confined to the manu-
facture of rails and some other descrip-
tions of railway material. The Exhibi-
tion of 1878, on the contrary, affords
clear evidence that Bessemer metal is
now in most countries employed for pur-
poses for which only a few years ago it
was not generally considered sufficiently
good. It appears also to have already
become very evident that the formerly
only too prevailing view that Bessemer
metal must necessarily be inferior to
othe'r ingot metal only resulted from cer-
tain Bessemer works which produced
both Bessemer and open-hearth metal,
employing for the former more impure
materials than for the latter. Where
similar materials are used in each case,
the ingot metal may be as good from the
Bessemer converter as that from other
sources. In other words, the quality of
the ingot metal is not so much depend-
ent on the methods, Bessemer, Siemens-
Martin, or crucible melting, as on the
purity of the materials, and the care with
which the products are sorted according
to their degree of hardness. To sum up
here all the purposes for which this Ex-
hibition proves that Bessemer metal has
been employed would carry us beyond
the compass of this short paper, but it is
perhaps right to point out some of them.
Thus in the French division, Lobel and
Turbot exhibit heavy chains, welded in
the common way, made of Bessemer iron
from La Societe des Forges de Denain et
d'Anzin. In the same way, Ernest Der-
vaux-Ibled manufactures railway wagon
couplings, screw-bolts, and other similar
articles of Bessemer iron, from the Bes-
semer works just named. Further, not
only several French makers, such as
David, Damoizeau, Doremieux Fils and
Cie., and the Societe de Commentry
Fourehambault, but also Brown, Bayley,
and Dixon, of Sheffield, have exhibited
heavy Bessemer chains without weld,
produced on nearly the same principle as
has long been employed for lighter
chains, as dog-couplings and such like.
La Compagnie des Fonderies, Forges, et
Acieries de Saint Etienne exhibits Bes-
semer rings for cannon. Similar articles,
we learn, are also produced at Seraing,
whose beautiful display, like several
others, as, for instance, those of the
Oesterreichische Staats Eisenbahn Ges-
ellschaft in Hungary, and Demidoff in
Russia, comprehend good boiler-plate of
Bessemer iron. Similar boiler-plate was
also exhibited by the West Cumberland
Iron and Steel Company, and to give an
idea of its good quality, a large hole has,
by the help of dynamite, been driven
through the middle of the plate without
its being possible to see that any portion
of the plate has been wrenched away by
the violent 'explosion; for the hole is
bounded by edges that have been bent out
at right angles, but have not been torn off.
Both the evenness and excellent quality
of the Bessemer, as well as the Siemens -
Martin plate, and the very great superior-
ity of both over plates of puddled iron,
are seen most clearly by the exhibit of
the Swedish Iron Board (Fercontoret),
which shows that the ingot plate, when
tested with a falling weight, withstood
from five to nine blows from a height
of 4.5 metres without the least fail-
ure; while the Swedish iron plate only
withstood four to six blows of the
same weight from a height of only 1*5
metre, or a third of the height in the
ingot-plate tests. Further, in these tests,
with a falling weight, the buckling be-
ADVANCES IN THE MANUFACTURE OF IRON AND STEEL. 461
fore the least sign of fracture averaged the Staffordshire plate, 0.203. In addi-
150 to 160 mm., while the Swedish plate tion to this difference in the content of
of puddled iron never permitted before phosphorus, there is also in the Stafford-
fracture greater buckling than 104 mm. ' shire plate a larger quantity of silicon,
Nevertheless, the Swedish iron plate was, or more probably of cinder. No proper
as such, of very superior quality, for difference between Bessemer and Sie-
tests, made with the same falling weight; mens-Martin plates could be discovered
of best best Staffordshire and best York- j in the course of these experiments, which
shire plates showed that the former gave comprehend both complete analyses and
way at the first blow from a height of tension tests. Yet it almost appears as
only 1 metre, while the Yorkshire plate if the Martin plates have a somewhat
at the utmost withstood three blows from greater ductility than Bessemer plate
a height of 1.5 metre, and showed in ' with the same content of carbon. This
that case a buckling of 68 mm. When ' is also confirmed by the numerous and
the height of fall of only 1.5 metre used complete tables of breaking and other
for the puddled plates was employed for tests included in the beautiful exhibit of
the ingot plate the latter withstood the Oesterreichische Staats Eisenbahn
twenty-five blows, while, on the other Gesellschaft. From these it appears to
hand, the weight at the first blow passed follow that the Bessemer metal made by
through even the Swedish plate of pud- this company at Reshicza has, in general,
died iron when the fall-height of 4.5 a somewhat greater tensile strength, but,
metres used for the ingot plate was also at the same time, also less ductility, than
employed for it. Tests were also made Martin metal of corresponding degrees
for the ingot plate with a fall from a ' of hardness from the same works. These
height of up to 9 metres, when it with- 1 differences, however, probably depend
stood before fracture three blows with j not so much on the method of produc-
tive same buckling as in the case of the ! tion as upon a trifling excess of the con-
lower height, also before fracture. Plates i tents of phosphorus and silicon in the
of Swedish iron made on the Lancashire \ Bessemer over the Martin metal, made
hearth, as might have been expected be- from materials of equally good quality,
forehand, appeared in respect to its ' The Siemens-Martin lends itself more
qualities to lie between those of puddled | readily than the Bessemer process to the
iron and those of ingots, inasmuch as it production of large and heavy pieces, in-
was much better than the former, but far asmuch as there is naturally much less
inferior to the latter. The ball used as a
falling weight in all these tests had a
weight of 875 kilogs., spherical in its
lower end, and a diameter of 253 mm.
difficulty in simultaneously melting in
several large Siemens furnaces, for which
no blast is required, that in blowing in at
the same time several Bessemer convert-
The interior diameter of the iron foun- i ers. This is also the reason why the
dation to which the plates were fastened | Compagnie des Forges et Acieries de la
during the tests with thirty-six rivets in | Marine et des Chemins de Fer, which
a double row was 537 mm. The diameter uses Bessemer metal for its smaller can-
of the falling weight was thus to the non, makes the larger of open-hearth
diameter of the part of plate exposed metal. The largest ingot which is to be
to buckling as 10 to 21. All the plates I found in the Exhibition was, probably,
were 9 mm. thick and 1 metre in diame
ter.
These experiments, besides, show how
enormous is the influence which the con-
tent of phosphorus exercises on the
power possessed by iron of resisting
blows; for the main difference between
the chemical composition of the different
puddled plates lay in their quantity of
phosphorus, for while the Swedish pud-
dled plates contained only 0.016 to 0.021
per cent, of phosphorus the percentage
in the Yorkshire plate was 0.094, and in
from the cause just named, made by the
Siemens-Martin process. For Oreusot
shows in its splendid and well-filled Ex-
hibition pavilion a representation t in
natural size of an ingot made in this way,
weighing 120,000 kilogs. The largest
actual ingot which is shown is also made
by the same process, and is to be seen in
the no less beautiful exhibit of the above-
named Compagnie des Forges et Acieries
de la Marine. Siemens-Martin iron is, as
is well known, employed to a greater ex-
tent than Bessemer for plates, axles, and
462
VAJT TsTOSTKAND7 S ENGINEEKING MAGAZINE.
other nice purposes, of which also the
Exhibition yields such numerous speci-
mens that it is perhaps unnecessary to
notice any separate examples. I there-
fore confine myself to pointing out how,
among others, both the above-named
works, the Compagnie des Forges et
Acieries de la Marine and des Chemins
de Fer and Creusot, use Martin steel for
rings and tubes for cannon, and Martin
iron for heavy armor plates. John Brown
and Co. and Charles Cammel and Co. also
exhibit heavy armor plates, consisting
partly of ingot iron, for these plates are
not exclusively made of it, but consist of
about half of puddled and half of ingot
iron. The plates are said not to be
welded together in the common way of
thick puddled and ingot iron laid upon
each other, but we learn that the union
of the different sorts of iron is brought
about at the former works by casting
fused iron over a properly-heated pud-
dled iron plate provided with a high iron
border, while Cammel makes his double
plates by melting down the ingot iron in
a furnace whose bottom, so to speak, con-
sists of the puddle iron plate, and then
letting them cool together. Both these
processes are, of course, finished by roll-
ing. The methods of working just de-
scribed, as well as the fact before refer-
red to, of Bessemer chains without and
with weld, certainly prove the ground-
lessness of apprehended difficulties in the
welding of ingot iron. That heavy armor
plates even can be produced of open-
hearth metal, by piling and welding to-
gether in the way commonly used for
puddled iron, is, however, shown by the
Compagnie des Forges et Acieries de la
Marine, which, along with its ingot
plates, made each of an ingot, also shows
an armor-plate 0'56 metre thick, 4*20
metres long, and 1*42 metre broad,
weighing 26,500 kilogs. This plate was
produced by piling and welding together
an anormous number of ingot iron bars.
Besides, not only two Swedish exhibits,
but also those of the Oesterreichische
Staats Eisenbahn Gesellschaft and others
afford the clearest evidence that if the
ingot metal is only of sufficiently pure
quality, it is possible to weld completely,
not only the softest qualities, but also
very hard Bessemer and Martin metal.
The idea of producing armor-plates by
piling and welding together ingot iron,
instead of making it of a single large
ingot, is grounded on the fear that if
there be any defect in the ingot, the
whole of the plates made from it would
thereby be rendered unserviceable, while,
on the other hand, when many different
layers are welded together, a defect oc-
curring in any of them would not have
so great an influence on the plates. The
maker of such plates is, in other words,
influenced in this point by the same fear
which leads to rings for cannon being
produced by the welding together of
spirals, instead of making them in the
common way for tiers by the punching
and rolling of an ingot. In the same
proportion, however, as greater experi-
ence and care lead to greater success
being attained in producing more reliable
ingots, the more complex method of pil-
ing and welding ought to be less fre-
quently used. In any case, the series of
experiments on plates above referred to
as included in the exhibits of the Swedish
Iron Board,- are in my opinion so con-
clusive as to the superiority of the ingot
plates over the puddled plates in the case
of violent blows, that there can scarcely
be any doubt but that soft ingot iron will,
in course of time, completely replace
puddled iron for armor-plates. The dif-
ficulty is to find the right degree of soft-
ness and to learn properly to handle the
less easily-managed ingot iron. The
largest armor-plate which the Paris Ex-
hibition has to offer is of puddled iron,
made by Marrel Freres, and has the fol-
lowing dimensions: — Length, .4.250
metres; breadth, 1.600 metre; thickness,
0.715 metre; and weight, 38,022 kilogs.
As we have now seen not only how soft
ingot steel, but in recent times even soft
ingot iron, has begun more and more to
take the place of wrought iron, it may
not perhaps be out of place to point out
in a few words how it has become possi-
ble to produce this soft ingot iron which
has shown itself to be so superior. There
are, indeed, some exceptional Bessemer
works, as, for instance, Westanfors in
Sweden, where, without any extra addi-
tion, the softest iron can be made with-
out its suffering from any red-shortness,
and this, as is well known, is more easy
of accomplishment in proportion as the
pig iron employed contains, on the one
hand, more manganese, and, on the other,
less sulphur. If a product free from red-
ADVANCES IN THE MANUFACTURE OF IRON AND STEEL.
463
shortness is to be obtained, however, it is
in general necessary, at the close, not
only of the Bessemer, but also of the
Siemens -Martin process, to add an iron
more or less rich in manganese, and the
quantity of manganese added must in-
deed be greater in the same proportion
as the product is desired to be softer or
poorer in carbon. This was the reason
why Bessemer and Martin iron of proper
softness could only be produced excep-
tionally until there was a supply of iron
compounds very rich in manganese. For
as compounds of iron and manganese
commonly contain more than 4.5 per cent,
of carbon, no great quantity of such a
compound can be added, even to the iron
poorest in carbon, without the content of
carbon in the final product being so great
that it ought not to be counted as iron,
but as steel. As now, as has been stated,
an addition of manganese, the amount
of which must be ascertained in every
separate case, in order that an ingot
metal decarburetted to a certain degree
shall be free of red-shortness, it follows
that the richer in manganese the added
substance is, the less of it requires to be
used, and the less carbon accordingly is
carried into the final product, or, in other
words, it can be made the softer. This
was already seen by several persons in
the middle and towards the close of the
decade 1860-70, and in particular, Mr.
Kohn sought by articles in the news-
paper Engineering to draw the attention
of the makers of Bessemer and Siemens-
Martin metal to the importance of using
the iron compounds then considered rich
in manganese, as containg 20 to 30 per
cent., which were manufactured by Mr.
Henderson at Glasgow in 1866 and 1867.
This advice, however, was fruitless, and
the manufacture of ferro-manganese soon
came to an end from want of demand
for the costly product. The matter, how-
ever, was soon taken up again by Ter-
renoire, which, thanks to its eminent en-
gineer, Mr. Walton, understood better
than other Bessemer works, the advanta-
ges which more manganiferous iron com-
pounds were calculated to confer, and
therefore purchased not only Henderson's
but also Prieger's patent for the manu-
facture of ferro-manganese.
Since Terrenoire took the matter in
hand the methods of producing this
article have been rapidly improved, so
that very soon ferro-manganese made in
a Siemens furnace with from 50 to 60
per cent, manganese was offered for sale.
The process of manufacture was still,
however, costly, and the product, there-
fore, dear. The price, on the other hand,
fell rapidly, when by the help of regen-
erative heating apparatus of the Siemens-
Whitwell or Siemens- Co wper systems
and very basic charges, success was
attained in producing in coke furnaces
ferro-manganese compounds, with over
80 per cent, manganese. Of the exten-
sion which the manufacture of ferro-
manganese in the blast furnace has since
undergone, the Exhibition gives a good
idea, inasmuch as specimens, with more
than 70 per cent, manganese, are shown
by so many works that it is, perhaps,
unnecessary here to enumerate them.
The richest in manganese, with 87 per
cent., is, however, made by les hauts
fourneaux de Saint Louis, at Marseilles,
now the seat of the most extensive
manufacture of ferro-manganese. The
furnaces under the management of
Professor Jordan are, besides, the first
which in France began to utilize on a
great scale the rich and pure ores in
which the coasts of the Mediterranean
are so rich, and which have become.of so
great importance for the French iron
manufacture. Besides spiegeleisen and
ferro-manganese, there are manufactured
here, all with coke, pig for steel for
puddling, as well as Bessemer and Mar-
tin pig, along with a pig which is
employed in competition with charcoal
pig in Franche Comte forges, and finally,
pig for malleable castings. The supply
of ferro-manganese has led to a new
method being employed for utilizing old
worn-out rails, rich in phosphorus, begun
at Terrenoire in 1874, and since very
extensively followed. It has been long
known that phosphorus has to a certain
degree the same influence on the qualities
of iron as carbon, inasmuch as both these
substances diminish the ductility of the
iron, but increase its hardness, modulus
of elasticity, tensile strength, and dispo-
sition, when heated, to take the crystal-
line texture, with the resulting difficulty
of working at very high temperatures,
and brittleness in the cold state. The
great difference between the influence of
the substances, however, is that the
action of carbon is much greater than
464
VAN NOSTRAND'S ENGINEERING MAGAZINE.
that of phosphorus in improving the
qualities of iron by increasing its hard-
ness, modulus of elasticity, and tensile
strength, while on the other hand the
influence of phosphorus far surpasses that
of carbon in deteriorating its qualities
by increasing the disposition to form
crystals and by diminishing the ductility.
Further, it had also been ascertained that
the influence of phosphorus on the
qualities of iron is increased in a very
high degree by the simultaneous pres-
ence of a large content of carbon, so that
the change in its qualities depending on
a certain content of phosphorus is much
greater in a steel rich in carbon than in
an iron poor in carbon. These relations
Terrenoire turned to account in the em-
ployment of its ferro-manganese. For
by its help, it could, as has been already
said, without danger of red-shortness,
produce a final product so poor in carbon
that the injurious influence of phosphor-
us upon it became much less than it
otherwise would have been. Besides, it
was possible, without to great an in-
crease in the content of carbon, to obtain
in the final product a considerable
content of manganese, which had the
double advantage that the manganese
appeared at the same time to counteract
the injurious influence of phosphorus on
the iron, and in some degree to increase
its hardness. The result of all this is,
that while in so simple an object as rails,
the quantity of phosphorus that could
be permitted in an ingot steel with 0.5 to
0.6 per cent, carbon was scarcely 0.1 per
cent., there may now with 0.2 to 0.3 per
cent, carbon and 0.5 to 1.00 per cent,
manganese be as much as 0.2 to 0.3 per
cent, phosphorus. For rolling rails con-
taining so much phosphorus there is
required a more powerful rolling train
than for purer carbon steel rails, partly
because the more phosphoriferous ingot
metal requires a greater extension, in
consequence of which the ingots must be
larger, and partly because ingot metal
containing an excess of phosphorus can-
not bear to be heated to so high a
temperature as the less phosphoriferous.
Nevertheless the product is, of course,
inferior, both through increased brittle-
ness and diminished hardness; but it
appears as if it might be good enough
for rails, at least in countries with a mild
climate, and great are the advantages
which the metallurgist has already been
able to draw from this, not only in
melting down and re-rolling old iron
rails, but also through its being possible
to use at Bessemer works a somewhat
more phosphoriferous pig than before.
In connection herewith I also beg to be
allowed to point to the interesting series
of experiments on the influence of car-
bon, phosphorus and manganese, on the
physical qualities of iron, shown in the
exhibits of Terrenoire. In general these
experiments confirm what was before
commonly accepted in this way, but
there is one thing that forms an excep-
tion to this. The tension experiments
made in Sweden appeared to show that
the percentage of elongation at breaking
is diminished with the content of phos-
phorus, while from the Terrenoire
experiments, on the other hand, it
appears as if a content of phosphorus of
up to 0.3 per cent, had no special influ-
ence on the percentage of elongation at
breaking. Should this observation come
to be confirmed by continued experi-
ments, it would afford the clearest proof
of the insufficiency of tension tests alone
as a means of judging of the goodness of
iron, for the Terrenoire and the Swedish
experiments agree in another point,
inasmuch as they both show that phos-
phorus very considerably increases the
sensitiveness of iron to blows. Even if
tension tests of phosphoriferous iron
give excellent results, increased tensile
strength and undiminished percentage of
elongation, it is nevertheless both in tests
of a falling weight and of daily experi-
ence a settled matter that an exceeding-
ly small content of phosphorus has an
injurious influence on the power of
resisting blows even of iron poor in
carbon. It is not, therefore to be
wondered at if the metallurgist devotes
the greatest attention to the important
question how phosphorus can be re-
moved from iron. That this may be
done to a high degree by suitable pud-
dling at the same time that the quantity
of phosphorus remaining in the puddled
iron has not so injurious an influence on
it as it has upon the more cinder-free
refined iron of the Lancashire fire, and in
a yet higher degree upon the quite
cinder-free ingot iron, are facts which
have been long known. This is, perhaps^
easily explained by the lamellae of cinder
ADVANCES IX THE MANUFACTURE OF IRON AND STEEL.
465
counteracting the crystalline texture,
with the resulting brittleness which
phosphorus produces. Again, that pud-
dling purifies from phosphorus so much
more than the other refining processes
depends, as is well known, on the cir-
cumstance that phosphorus must be
removed from iron as a salt of phosphor-
ic acid passing into the cinder, and
neither the Bessemer nor Lancashire
refining processes admit of this in a
degree comparable with puddling. In
order that the salt of phosphoric acid
may be able to remain unchanged in the
cinder, the latter must not be too acid or
rich in silica, and its temperature must
not be too high, for then the silica drives
out the phosphoric acid, which, when set
free, is immediately reduced by the
carburetted iron with which it comes in
contact, and enters into combination
with the same. This is the case in the
Bessemer process. Again, that Lanca-
shire refining purifies iron from phos-
phorus in so much smaller a degree than
puddling depends, without doubt, on the
fact that charcoal in the open hearth is
found in contact both with the iron and
the cinder; and though the latter is
commonly somewhat richer in protoxide
of iron than in the case of puddling, and
therefore ought to purify still more from
phosphorus, this action is neutralized by
the pieces of charcoal present, which
reduce most of the phosphoric acid con-
tained in the cinder that has passed into
it, and thereby returns the phosphorus
to the iron.
To how great a degree success has re-
cently been obtained in freeing iron from
phosphorus by adding rich iron ore or
other materials rich in oxidized iron
during puddling, appears very clearly
from several French, Belgian, and
English exhibits, which, though the ores
employed are so phosphoriferous that
their pig contains 1 to 1.5 percent, phos-
phorus, yet show so beautiful cold work-
ed specimens of their iron, that one not
familiar with the facts would have diffi-
culty in believing that the raw materials
employed were so rich in phosphorus as
in fact they were. All other exhibits of
puddled iron are, however, in this re-
spect far surpassed by that of Hopkins,
Gilkes, and Go. of Middlesbrough, which
show cold-worked samples of such excel-
lence of iron, that one would far more
Yol. XIX.— No. 5—30
readily believe that they were made from
ores nearly free from phosphorus than
from those of Cleveland, famous for the
1 quantity of this substance which is found
j associated with them, and which yield a
pig containing 1.5 per cent. This iron
; is made, as is well known, in rotating
! puddling furnaces; and it ought to be a
j pleasure for all who have taken part in
j the difficulties with which machine pud-
dling has had to contend, to see that un-
| tiring perseverance appears at last to
I have gained its well-deserved reward.
| It would, however, ill become me to seek
t to enter further on the question of the
superiority of the rotating puddling
furnaces over fixed ones, as it is just this
honored Association which has spread
abroad nearly all the knowledge that is
to be found regarding this subject. As,
however, at the meetings of this Insti-
tute different furnace constructors have
sometimes sought to hold out the greater
effectiveness in purifying from phosphor-
us, as specially distinctive each of his
own puddling furnace, I cannot omit to
give expression to the view that it ought
to be a point of superiority, common to
all rotating puddling furnaces, that they
purify from phosphorus more than fixed
ones; for the more the phosphoriferous
\ iron is exposed to the action of the fet-
tling, rich in protoxide of iron, the more
phosphorus ought to be removed; and it
would be perhaps difficult to bring about
! in a fixed furnace a contact between
i these materials so often repeated as is at-
i tained by the rotating puddling furnace
j without manual labor. Iron made in the
| rotating puddling furnace is also exhibit-
ed both by Creusot and by the Compagnie
des Forges de Donain et d'Anzin. The
( latter works has a Crampton's f ur-
j nace, while Creusot has for more than two
j years had at work two modified Danks
: furnaces, with a double plate covering,
through which water circulates. Such a
furnace is to be seen in the magnificent
pavilion of Creusot. The iron made with
it is stated to be nearly free from phos-
phorus, but it is also manufactured from
| a pig very poor in phosphorus. It is
i clear from the foregoing that one way of
i producing ingot metal, even from very
j phosphoriferous pig, would be first to
puddle it in a rotating furnace, and then
to fuse the puddled iron thus obtained
with pig poor in phosphorus. But, on
466
VAN NOSTRANCTS ENGINEERING MAGAZINE.
the one hand, such puddled iron, not-
withstanding the beautiful cold- worked
specimens exhibited, is not in general so
poor in phosphorus as is desirable for in-
got metal of first-rate quality, for Hop-
kins, Gilkes, and Co.'s iron, according to
the analyses given, contains from 0.08 to
0.1 1 per cent, phosphorus; and, on the
other hand, such iron, up to this time at
least, has not been made so cheaply that
it could be expected to compete in the
way that has just been pointed out with
Bessemer metal, now so low in price.
The great importance which the ques-
tion of how ingot metal is to be produced
from very phosphoriferous raw materials
has, for such a district as that of Cleve-
land, gave occasion, as is well known, to
the very thorough and interesting re-
searches of Mr. I. Lowthian Bell. With
the same frankness and love for scientific
enlightenment which induced him
formerly to lay before this Institute his
comprehensive researches regarding the
blast furnace, which placed it in an alto-
gether new light, he has also, in several
memoirs which have been read with the
greatest interest over the whole world,
given an account of his attempts to
purify pig iron from phosphorus. By
these experiments Mr. Bell has, in the
most indubitable way, not only confirmed
and thrown still further light on what
science had formerly more or less thor-
oughly ascertained in this department,
but he has, moreover, succeeded in de-
vising a method of applying on a great
scale the scientific results at which he has
arrived. He has also communicated so
much on this point to this Institute that
it would be unnecessary, not to say im-
proper, for me to discuss this subject
further, were it not the aim of this paper
to endeavor to point out the most inter-
esting objects which are to be found in
the Paris Exhibition relating to the
manufacture of iron and steel; and what
iron metallurgist can well deny that Mr.
Bell's exhibit has an interest with which
scarcely any other than that of Terre-
noire can come into comparison. I
ought, therefore, perhaps to be forgiven
if, notwithstanding all that Mr. Bell him-
self has already communicated to this
Association regarding his plan of puri-
fying from phosphorus, I, too, beg to say
a few words on this subject. For a long
time back there has been employed in
some districts, as is well known, a pre-
paratory refining process in a separate
hearth or furnace, after which the pig
which had undergone this process was
finally refined to malleable iron in an-
other hearth or furnace. The object of
this preparatory refining was partly to
diminish the content of silicon in the pig
iron, and thereby render it more suitable
for the final refining process, and partly
to diminish the percentage of phosphorus
in the pig iron, and thus obtain a less
phosphoriferous final product. Both
these objects Mr. Bell has had in view
with this process, but he has succeeded
far better in attaining them than' had
been done previously, the reasons of
which we shall soon see. In- the com-
mon running-out fires the pig iron is
melted in contact with the fuel, and even
if substances rich in oxidized iron are
added to it, it is certain that the purifica-
tion from phosphorus can never in this
way be complete; but when we consider
the fact already stated, that the Lanca-
shire hearth refining purifies from phos-
phorus to a very inconsiderable degree,
we rather find occasion for surprise that
the common running-out process can take
away so much phosphorus as it do-es.
The reason, however, lies in the following
two differences between hearth-refining
and the running-out process : — (1) In
the former the phosphorns, which has
been taken up by the cinder as a salt of
phosphoric acid, comes into simultaneous
contact with carbon and more or less de-
carburetted iron, and it is a fact, which
is proved by several circumstances, that
iron combines both with phosphorus and
several other metalloids with greater at-
tractive force in proportion as it is purer
and more refined. In the running-out
fire, on the contrary, the pig iron is never
decarburetted in any noteworthy degree,
and it therefore never acquires so strong
a disposition to reduce the phosphorus
out of the cinder and again enter into
combination with it. In the running-out
fire, too, the fused iron in general does
not come into simultaneous contact with
the cinder and carbon, but a cinder bath
is interposed between the fused iron and
the carbon, while, on the contrary, the
iron during the operations in the refining
hearth comes into such simultaneous
contact with the cinder and carbon as
has as its result the reducing of the
ADVANCES IN THE MANUFACTURE OF IRON AND STEEL.
467
phosphorus and its re-combination with pig is run out into cakes, which it is then
the iron. (2) In the refining hearth the the intention to melt down, along with
iron is subject during the latter part of
the process to a higher temperature than
is the case in the running-out fire.
The running-out fire process has excep-
tionally been carried on in a reverbera-
tory furnace without contact with the
fuel, and as the purification from phos-
some rich iron ore poor in phosphorus,
in a Siemens regenerative furnace with-
out crucibles, to ingot metal according
to the Landore method. Mr. Bell, how-
has not for the present any such
ever.
furnace at his disposal; and the specimens
of ingot metal included in his exhibit,
phorus which takes place in the puddling : accordingly, have not been produced by
furnace is so much more complete than himself, but have been prepared accord-
that which is accomplished in the Lanca- j ing to his method from Cleveland pig at
shire refining hearth, we might well have Woolwich, where the smelting has pro-
supposed that a reverbcratory furnace I ceeded in a furnace of Mr. Price's well-
would be distinguished in the same way ' known construction. This has its pecu-
in comparison with a common running- j liar interest, as the circumstance that
out fire. As reverberatory furnaces have i soft steel and iron may be kept fused in
been arranged, this, however, has scarce- j Trice's furnace further confirms the fact
ly been the case; and the reason of this \ already proved, by the low consumption
is not difficult to find, when we consider of fuel, that this furnace is in a high de-
that such furnaces have been lined with
gree
As Mr. Bell's pro-
sand or masses of quartz, which prevent cess has only been employed experiment-
the cinder from being sufficiently basic ■ ally, it is of course yet too early to give
or rich in oxidized iron; and we ought l an opinion on its future. The first ques-
never to forget the fact already touched j tion with reference to it is, whether it
upon, that, if any considerable purifica- . can be got to work so uniformly that the
tion from phosphorus is to be brought I purification from phosphorus will be al-
about, the cinder must always be kept
so basic that the silica is well saturated,
and so has not too strong a disposition
to liberate from the cinder the phos-
phoric acid, which is then reduced,
and enters into combination with
the iron as phosphorus. All these de-
fects, inseparable from the old method
of refining, Mr. Bell has now succeeded
in avoiding by running pig iron rich in
ways equally complete, and the product
accordingly quite reliable. This ought
best to be attained by the help of a self-
acting furnace. The second question is
whether this method can be made cheap
enough, so that the ingots thereby pro-
duced will be able to compete in work-
ing expenses with Bessemer ingots. A
main factor in judging of these questions
is the endurance of the lining of the re-
phosphorus into a reverberatory furnace, ' fining furnace. If it can be got to stand
lined with iron ore, or some other sub- 1 pretty well, the process itself goes on so
stance, rich in oxidized iron, and then, at fast that the refined product must be
a temperature not exceeding that which quite cheap. As, besides, it consists
is required to keep the pig fluid, by j almost exclusively of iron and carbon, its
bringing about, either by the nature ; decarburretting with rich ore ought to
of the furnace itself or by stirring, a ! proceed in a considerably shorter time
powerful action of the peroxide of iron than is commonly required for the open
on the pig. The result of this has been hearth process, and there thus appears to
striking ; a ton of molten pig iron, with i be a good prospect of producing from a
1.8 per cent, silicon, 1.4 per cent, phos-
phorus and 3.5 per cent, carbon, being
changed in ten minutes into a product
with only 0.05 to 0.1 per cent, phos-
phorus and 3.3 per cent, carbon. The
pig, rich in phosphorus, an ingot metal
both cheaper and poorer in phosphorus
than is possible by machine puddling.
The final determining factor will, of
course, be the difference in Bessemer pig
waste is only about 2.5 per cent. Several j produced from ores poor in phosphorus,
different kinds of reverberatory furnaces and the Cleveland rich in phosphorus, and
have been tried for this purpose, but Mr. Bell's process ought, therefore, at
that which for the present is believed to least, to become a regulator of the excess
be the most suitable is Pernot's flat fur- i in price of the sorts of pig which are poor
nace on an inclined axle. The refined I over those which are rich in phosphorus.
468
VAN NOSTKAND7S ENGINEEKING MAGAZINE.
As the drawn out ingot metal has re-
cently more and more replaced the
wrought iron, steel castings have also
more and more encroached upon the ter-
ritory of iron castings, inasmuch as a
great many things, in which more than
ordinary strength is required, are now
cast in steel instead of iron. For this
purpose crucible steel has been used for
a long time back, but it has since become
more common to employ, not only Sie-
mens-Martin, but also Bessemer steel.
The Exhibition is so rich in Siemens-
Martin castings, that it would not repay
the trouble to enumerate the different
exhibitors, but Angleur, in Belgium,
ought, perhaps, to be mentioned as ex-
hibiting Bessemer castings of more than
common merit. In order that the cast-
ings may be considered of first-rate
quality, it is, of course, requisite that they
be compact, and the greatest difficulty in
their production is, as is well-known,
just the fulfilment of this main condition.
As the blow-holes in steel are caused by
the escape of gases which have not reach-
ed the upper surface of the casting
previous to its cooling, and as, further,
this escape of gas arises partly from the
gases which the steel has taken up during
its formation or melting, and partly from
the carbonic oxide which is formed by
the action of the oxygen distributed
through the steel, or, perhaps, more cor-
rectly of oxide of iron upon the carbon
of the steel, it is easy to understand that
the difficulty of getting steel castings
compact is least with crucible melting,
greater with the Siemens-Martin, and
greatest with the Bessemer process. So
long as the castings are made of hard
steel, the difficulties in this respect are,
however, comparatively easy to get over,
but in steel castings a greater ductility
is often required than that which hard
steel possesses, and it is, therefore, neces-
sary in many cases that the steel be soft,
with only 0.5 to 0.6 per cent, of carbon.
A very common way of attaining this
end is to cast pieces of very hard steel,
and afterwards, in the same way as is
common in the production of malleable
castings, to subject them to heating in a
powder of oxides of iron, which dimin-
ishes the content of carbon in the steel
castings from without inwards. Com-
pact steel castings, with the ductility in-
creased in this way, are also exhibited
from several works, as, for instance, by
Dalifol in Paris and G. Fischer at Schaff-
hausen. A method that has been long
employed to promote freedom from
blow-holes in steel castings is to add a
pig iron rich in silicon to the soft steel
while it is being melted, for the thus in-
creased content of silicon in the steel
counteracts, as is well known, both the
taking up of gas during melting and the
formation of carbonic oxide during the
cooling of the cast steel. The common
content of silicon in the products of vari-
ous works famous for their compact
steel castings has, therefore, been' about
0.30 per cent. Thanks to its more than
ordinary skillful engineers, M. Walton
and his successor M. Pourcel, and a man-
agement with correct application for the
requirements of the times, Terrenoire
has now further developed this manu-
facture by adding at the close of the
melting of the steel so-called " fer-man-
ganese-siliciurn," or a pig iron rich in
manganese and silicon. The richest
specimen of this which the Exhibition
has to show contains 20.5 per cent, of
manganese and 10.5 per cent, of silicon.
The advantage of this is, that when the
oxygen dissolved in the steel or the oxide
of iron comes into simultaneous contact
with manganese and silicon, both these
substances are oxidized, and there is
formed a double silicate of protoxide of
iron and manganese, more fusible and
fluid than the silicate of protoxide of
iron, which is formed when only a pig
iron is added which is rich in silicon but
poor in or free of manganese. Through
the greater fusibility and fluidity of the
silicate thus formed, there is naturally a
diminution of the danger that it will not
completely rise to the upper surface of
the steel and there separate itself as a
layer of slag, but remain in the interior
of the casting as a network, and thus di-
minish its strength. It is clear, how-
ever, that it is not necessary for this pur-
pose to use " fer-manganese-silicium,"
which must be very difficult to manu-
facture, inasmueh as the obtaining of the
greatest possible quantity of manganese
in a pig iron demands conditions on the
blast furnace burden quite opposite to
what is necessary for attaining the great-
est content of silicon; for the former re-
quires the minerals not only to be very
rich in manganese, but also to be as basic
ADVANCES IN THE MANUFACTURE OF IRON AND STEEL.
469
as possible, while for the production of
silicious iron it ought to be as acid as
possible. The end in view, viz., the sim-
ultaneous addition of manganese and
silicon to the steel, ought as easily to be
attained by the addition of a fused
mixture of ferro-manganese and a very
silicious pig, and in such a case the dif-
ference is small from the method formerly
employed of using ferro-manganese in-
stead of spiegeleisen. The advantage of
the Terrenoire process is thus that by
means of it we can directly manufacture
a softer, and in consequence a more
ductile, but still compact product than
was previously possible. There are also
now produced at Terrenoire only steel
castings poor in carbon, for the hardest,
or those that are used for armor-piercing
projectiles, contain, according to an ob-
liging communication by M. Pourcel, not
more than 0.5 to 0.6 per cent, of this
metalloid.
It would appear from several publica-
tions in technical periodicals descriptive
of the Terrenoire process, as if silicon
has been found not only to promote the
compactness of steel, but also otherwise
to improve its qualities. This is, how-
ever, by no means the case; but experi-
ence at Terrenoire has completely
confirmed the old opinion, that the
greater the content of silicon in a steel,
otherwise of similar quality, the more
sensitive it is to blows. The addition of
silicon is considered simply as an evil
necessary for the sake of the compact-
ness of the steel wares, and great
importance is placed on net adding a
superfluous quantity of silicon, in order
that the content of it in the product may
not be greater than is absolutely neces-
For ingot iron and steel, which are
subjected to shingling or rolling, and
whose blow-holes, therefore, may be
rendered harmless by welding, M.
Pourcel will, on no account, employ any
addition of silicon. The most common
content of silicon in their steel castings
is stated to lie between 0.2 and 0.3 per
cent., and such a content of silicon is
considered pretty harmless. The very
considerable percentage of manganese —
0.55 to 0.7 — which their steel contains
doubtless contributes to this, for metal-
lurgists had previously believed that
they found that manganese counteracted
the injurious influence of silicon on the
qualities of iron.
At Terrenoire there has been a higher
aim set up by degrees in the production
of steel castings, and their very fine ex-
hibit shows that they now even reckon
on being able to substitute castings for a
number of articles for which malleable
iron or steel is used for the present. For
besides armor-piercing projectiles, both
massive and hollow, and cylinders and
other parts of hydraulic presses, there
are to be found exhibited not only tubes
but also rings for cannon, cranked axles,
and other similar unhammered castings.
Although all these articles are unham-
mered, both the surfaces of fracture ex-
hibited and the tension and other tests,
the results of which are communicated,
show that the physical qualities of the
finished products correspond pretty
closely with those which distinguish
hammered ingot metal with the same
chemical composition. On this point, as
is well known, various communications
have not only been made to this Insti-
tute, but others have appeared in various
journals, and I, for my part, confess that
nothing exerted on me a force so attract-
ive to the Paris Exhibition as just the
hope of being able there to find an ex-
planation of the problem, hitherto unex-
plained so far as I am concerned, by the
published communications to which I
have referred, viz, How the qualities of
ingot steel may be so changed without
hammering that they become comparable
with those of hammered steel. Xor has
this hope been disappointed, for from the
Terrenoire exhibit, and the printed de-
scription of it, it is clearly evident that
this alteration in the qualities of steel is
brought about by hardening. A rapid
cooling of a large piece of steel heated
to a red heat acts upon it in quite the
same w7ay as a hammering, for the con-
traction of the outer layer caused by
cooling must bring about a powerful
compression of the interior layers. In
order, however, that this action be suffi-
cient, it is necessury that the modulus of
elasticity of the material be so high that
the resistance of the inner layers to the
action of the outer do not produce in the
latter a set, or permanent extension,
whereby the compressing action is di-
minished. The iron intended for the
purpose ought, therefore, not to be tod
470
VAN NOSTKAND7 S ENGINEEBING MAGAZINE.
pure, for the modulus of elasticity of
pure iron is, as is well known, very low.
But, on the other hand, the content of
carbon in the material ought neither to
be too great nor the steel too hard, for
otherwise it is difficult to modify the
hardening that its action be not too
powerful when the ductility becomes
lessened and the product brittle. In this
way it is explained why it appears most
advantageous to keep the percentage of
carbon between 0.3 and 0.6, the lesser
quantity for larger and a greater for
smaller pieces, and in general to carry
out the hardening in oil. Should the
ularly employed except by Sir Joseph
Whit worth and Co., Manchester, where,
as is well known, this method has been
in use for more than ten years. Exceed-
ingly beautiful articles are exhibited by
this firm, world-famous for its accurate
workmanship, among which may specially
be mentioned a hollow cylinder with an
interior diameter of 1.98 metre, and a
length of 1.5 metre, and a thickness of
material of only 4 centimetres, a torpedo
guaranteed to resist an interior pressure
of air of 105 kilogs. per square centimetre,
and a hollow axle 10.26 metres long
with an exterior diameter of 45, and an
material be rather hard for the intended j interior of 30 centimetres. All these
purpose, the more moderate hardening pieces are made from hollow ingots,
which is produced by the cooling of the j which, when under preparation, are ex-
piece in air may be best, or the excessive ] posed to powerful hydraulic pressure,
hardening must be succeeded by a temper- ! after which the ingot that has been thus
ing whereby the ductility of the material treated is further worked by means of a
is increased. i hydraulic compression ; but, unfor-
If these explanations of the facts shown i tunately, it is impossible to obtain at the
by the Terrenoire exhibit be correct, it | Exhibition any more detailed account of
follows that if the best results are to be | this interesting method of working,
obtained, not only the hardening but also Finally, with regard to crucible-melted
the preparation of the steel must be
managed with the very greatest care and
attention. The melting is carried on at
Terrenoire in Siemens furnaces, without
crucibles, and Mr. Holley has, in the Met-
allurgical Review, given an interesting-
description of the way in which the
tool steel, the Exhibition has nothing
properly new to offer under this head, if
we do not consider chrome steel as such.
This, as is well known, is made by adding
a pig iron rich in chrome, and such a pig,
along with tungsten pig, is found, among
others, in the exhibit of Terrenoire. The
changes of the steel bath succeed each j iron compound richest in chrome, con
other, and, partly by the help of the ap-
pearance of the slag, partly by hammer-
ing samples taken out of the bath, the
proper moment is determined for adding
the compound of iron, manganese, and
taining up to 65 per cent., is however ex-
hibited by J. Holtzer, Dorian, et Cie.'s
steel works at Unieux, near St. Etienne,
and it is made by the reduction of
chrome ore with charcoal in the crucible.
silicon. For castings, compactness is The last-named exhibit also contains the
naturally of greater importance than for largest quantity of chrome steel. The
tension tests to which this steel and the
chrome steel from Terrenoire have been
ingots, which are afterwards to be drawn
out; but even for the latter compactness
is far from being a matter of indifference
if it can be attained without the sacrifice
of any other good quality, for unfor-
tunately the ingot blow-holes are far from
submitted have further confirmed the
statement previously made in other
quarters, that chrome still more than
carbon increases, not only the hardness,
being always properly welded together j but also the modulus of elasticity and
when the ingots are drawn out. It is | the tensile strength, while at the same
therefore not to be wondered at, that ex- j time it does not diminish the ductility so
periments have been made at many places I much as carbon. The action of chrome
to prevent the formation of blow-holes j is thus exceedingly advantageous, and
by means of powerful 'hydraulic pressure much resembles, but is believed to be
applied during the cooling and solidifica- still more powerful than that of tung-
tion of the cast steel or iron. This plan sten. Jacob Holtzer's steel, which is
has been tried at several places, as, richest in chrome, is said to contain 2.5
among others, at St. Etienne by V. Bie- per cent. The beautiful exhibit of See-
trix et Cie., but it has never been reg- bohm and Dickstahl, of Sheffield, also
REPORTS OF ENGINEERING SOCIETIES.
471
contains chrome steel, with only 1 per
cent, chrome. Wolfram or tungsten
steel is shown, not only by the exhibitors
of steel just named, but also by several
others, among which may be specially
mentioned the very beautiful exhibits of
crucible steel of, first and foremost, the
Innerberger Hauptgewerkschaft, but also
of Eibiswald in Stvria.
REPORTS OF ENGINEERING SOCIETIES,
American Society op Civil Engineers. —
The last issue of the " Transactions" con-
tains the following paper and discussions :
No. 162. The South Pass Jetties: Descriptive
and incidental notes and memoranda, by E. L.
Corthell.
Discussions on the South Pass Jetties, by C.
W. Howell. E. L. Corthell, C. Shaler Smith
and J. Foster Flagg.
Addition to Paper No. 160, by James B.
Francis.
This number also contains plates, from No.
XIY to XX inclusive, illustrating South Pass
Jetties, and Plate XXI showing the Mouth of
the Magdelena River.
Engineers' Club op Philadelphl\. — At
the last meeting of the Club, Professor
Lewis M. Haupt, President, read a memorial
to the State Legislature, praying that an ap-
propriation be made to co-operate with the
General Government in the more vigorous
prosecution of the Geodetic and Topographi-
cal Survey of the State, for the following
reasons :
1st. The imperative demand for such work
to supply correct maps for the true representa:
tion of the geology of the State.
2d. Correct maps are necessary to the
proper development of the State.
. 3d. To reform the sjrstem of land survey-
ing now the source of so many uncertainties
in consequence of the secular changes in
variation of the magnetic meridian; and,
4th. The ultimate economy of accurate
surveys.
The memorial closed with a statement of the
organization required for such works.
In supporting it, Mr. Ingham, Commissioner
for the Second Geological Survey, said that
they have found the present maps, boundaries,
&c, to be utterly worthless as regards accurate
location. In many cases requiring the geology
to be forced to fit county lines, and regretted
that this State had not already taken steps to
remedy this evil. After further discussion
action was postponed.
Mr. A. A. Roberts laid before the club the
original drawings for structures on the Alleg-
heny Portage Road (1831-6); among others
the plan of the first tunnel in America. These
he has recently discovered.
A letter from Mr. J. Christie, corresponding
member, was read in relation to simplifying
formulae for strains in rolled iron I, T and L
beams, giving result of some experiments re-
cently made.
Mr. Henry G. Morris exhibited plans of sev-
eral boilers, which he had used with good re-
sults, and showed comparative merits of each;
also plans of sugar-making machinery, with
detailed explanations.
Mr. Muckle presented drawing of Eave's new
safety valve, from "Atlas Steel and Iron
Works," and showed its advantages. Also
read a description of Haddan's Military or
Pioneer Railway, recently placed before the
Royal Institution, and, when on trial, a section
was erected at a speed equivalent to a mile a
day for every hundred men employed. This
was over uneven ground.
Louis C. Madeira, Jr ,
Secretary pro tern.
Premiums prom the Institution op Civil
Engineers. — The originality, labor, and
ingenuity displayed by the authors of some of
the communications submitted to the Society
during the session 1877-78 have led the Council
to make the following awards : —
For Papers read at Ihe Ordinary Meetings.
1. Telford Medals, and Telford Premiums,
to R. W. H. Paget Higgs, LL.D., and J.
R. Brittle, for paper on " Some Recent Im-
provements in Dynamo-Electric Apparatus."
2. A Watt Medal, and a Telford Premium, to
H. Dave}r, for paper on "Direct-acting or IS on-
rotative Pumping Engines and Pumps."
3. A Telford Medal, and a Telford Premium,
to T. Curtis Clarke, for paper on " The Design
generally of Iron Bridges of very large Span
for Railway Traffic."
4. A Watt Medal, and a Telford Premium,
to Bradford Leslie, for paper on " The Hooghly
Floating Bridge."
5. A Telford Premium to J. Atkinson Long-
ridge, for paper on "The Evaporative Power
of Locomotive Boilers."
6. A Watt Medal, and a Telford Premium,
to Alfred Holt, for " Review of the Progress of
Steam Shipping during the last Quarter of a
Century."
7. The Manby Premium to E. Bazalgette,
for paper on "The Victoria, Albert, and Chel-
sea Embankments of the River Thames."
Other medals were awarded for papers
printed in the proceedings without being dis-
cussed, and for papers read at the supplemental
meetings of students.
IRON AND STEEL NOTES-
O TEEL AT THE PARIS EXHIBITION. — The
kj numerous visitors to the Machinery Hall
must have observed an exceedingly choice as-
sortment of Messrs. H. Augustus Guy and
Company's Specialties, foremost among which
figures their well-known invincible tool steel
in the ingot, bar and representative tools. We
understand that these gentlemen, in the exer-
cise of their undoubted rights declined to admit
the jurors into the secrets involved in the mate-
rials and manufacture of their monopolies.
Consequently their exhibits were not adjudged
for awards. Of course, when a firm has de-
voted years to a valuable improvement, in a
commodity like tool steel, and is beginning to
472
van nostrand's engineering magazine.
feel the advantages of success, it certainly re-
quires much more than average self-abnegation
to disclose the details of their system to the
world. They, however, proposed a very am-
ple equivalent, so far as the jurors were con-
cerned, and the public more especially, in their
offer to submit sample bars of any size or sec-
tion for the most crucial tests, in competition
with all manufacturers, to make good their
claims to the highest honors, and it is to be
regretted that this course, which is, after all,
the only true criterion, was not adopted. We
had an opportunity this week of inspecting at
the firm's London office some new specimens,
which, we were informed, embody the discov-
ery and successful application of further im-
provements. Guy's ' ' True " boiler cleaner for
removing and preventing incrustations in land
and marine boilers was also exhibited, and
aroused considerable interest. It has a double
value, and meets a very serious difficulty — a
problem which a protracted inquiry on the part
of our own Government has failed to solve sat-
isfactorily— for it prevents oxidization of the
boiler plates, while it also moderates priming,
and in this capacity must be of great value.
The Use of Steel for Structural Pur-
poses.— The final report of the committee
of the British Association on the use of steel
for structural purposes states : — "Having given
the subject our best consideration, we recom-
mend that the employment of steel in engineer-
ing structures should be authorized by the
Board of Trade under the following conditions,
namely: (1) That the steel employed should be
cast steel or steel made by some process of
fusion, subsequently rolled or hammered, and
that it should be of a quality possessing con
siderable toughness and ductility, and that a
certificate to the effect that the steel is of this
description and quality, should be forwarded
to the Board of Trade by the engineer respon-
sible for the structure. (2) That the greatest
load which can be brought upon the bridge or
structure, added to the weight of the super-
structure, should not produce a greater strain
in any part than 6£ tons per square inch. In
conclusion, we have to remark that in recom-
mending a co-efficient of 6% tons per square
inch for the employment of steel in railway
structures generally, we are aware thar cases
may and probably will arise when it will be
proposed to use steel'of special make and still
greater tenacity, and when a higher co- efficient
might be permissible, but we think these cases
must be left for consideration when they arise,
and that a higher co-efficient may be then al-
lowed in those instances where the reasons
given appear to the Board of Trade to justify
it." This report has since been acted upon by
the Board of Trade in the printed paper issue"d
by them in reference to railway structures. "It
will be observed that a coefficient of 6-J tons
per square inch is assigned to steel, that of iron
being 5 tons per square inch. This increase of
the co-efficient will effect important economy
in structures, especially in bridges of large
spans, and will also tend generally to increase
the employment of steel for railway and ship-
building purposes. The labors of your com-
mittee having ended in such a satisfactory
manner there is no necessity to re-appoint
them." The report is signed by Mr. E. H. Car-
butt, Mayor of Leeds, as Secretary.
The Mechanical and other Properties
of Iron and Mild Steel.— Numerous
experiments have been conducted by several
eminent engineers to prove the tensile strength
of iron and steel, both in the shape of bars and
plates. Unfortunately, however, many of the
tests have been carried out with rude testing
machines, rendering it difficult to obtain a true
result of the endurance and strength of the
metal under investigation. Some experiments
were conducted with a view to determine the
strength of steels with fixed proportions of car-
bon only, by Mr. Vickers, cf Sheffield, and
recorded by him in a paper read on the subject
before the Mechanical Engineers of England,
August 1st, 1861 ; but as these tests were more
especially resorted to to ascertain the strength
of crucible steels, mostly used for tool-cutting
purposes, they were of but little value to the
constructive or mechanical engineer. Mr.
Adamson, having used practically a compara-
tively mild class of steels or ingot irons for the
last twenty-one years, at times found, from cold
mechanical bending tests, some irregularities
in the working of the metals. This indicated
to him the necessity of more careful investiga-
tion, both as to their composition and the tem-
perature at which they could be manipulated
in the workshop and practically applied ; and
in the present paper his object was to put be-
fore the members a record of the endurance of
iron and steel when subject to concussive force
such as can be produced by gun-cotton, gun-
powder, or other explosive materials. The
experiments carried out were instituted with a
view to ascertain what would be the effect on
a steam-boiler working under pressure by the
side of an exploding boiler, or the effect on a
ship by a collision with another, and whether
wrought iron or steel possessed the greater
power to resist such accidentally produced
force. Uniformly the various trials made by
the writer in June, 1876, were favorable to
mild steel. Drift and tensile tests pointed em-
phatically in the same direction. The value of
steel and iron for structural purposes was also
tested, and contrasted with that of iron, the
result being to show that steel with about one-
half per cent, of carbon, 1 per cent, of manga-
nese, with a low measure of silicon, sulphur
and phosphorus, can be depended upon to
carry double the load of the best wrought-iron
Dlates that can be produced, and with as good
results as regards elongation. After many
trials and many failures in attempting to weld
steel boiler plates, the writer found it necessary
to ascertain in all cases the composition of the
metal before putting any labor upon it. From
a large experience it is now found desirable
that the carbon should not exceed one-eighth
per cent., while the sulphur and phosphorus
should, if possible, be kept as low as .04 silicon
being admissible to the extent of one-tenth per
cent. The writer then passed on to describe a
variety of tests of the malleability of iron and
steel, their powers of endurance under color-
KAIL WAY :S"OTES.
473
heat, &c, and followed with the observation
that from the experiments he had explained, it
would be apparent that the users of metals
must make some natural selection, as it were,
to secure the highest and best results for any
special purpose. It would also be clear that no
wrought iron could resist concussive force
equal to mild steel, and as a much higher range
of ductility and carrying power was attained,
he had no doubt constructive' engineers would
feel themselves constrained to use it much
more extensively in all cases where strength
and lightness were required. Should it ulti-
mately be proved that sea- water would destroy
steel quicker than wrought iron, the use of
wrought iron for the skins of ships might be
continued; but, with present knowledge, noth-
ing, in his opinion, existed to prevent the whole
framework of every steamer and sailing vessel
being constructed of Bessemer or Martin-Sie-
mens steel, as at least one-third the weight
might be saved at the same time that greater
security was ensured. In the diluted sulphuric-
acid bath the evidences were quite clear in
favor of mild steei and the purest iron to resist
corrosion, but before as much could be said as
to the influence of sea or salt water a more ex
tended and careful series of experiments would
be required. The same might be said of the
selection of metals for the construction of artil-
leiy; and the writer had no doubt that, by a
still more careful manufacture, to keep down
the carbon and injurious alloying substances
common to wrought iron, most enduring armor
plates might be manufactured by the Pneumatic
or Martin-Siemens process. Further, there
could be no doubt that the medium hard class
of steels, possessing double the strength of the
best wrought iron that can be made, ought,
without exception, to be used for building
bridges and numerous other like structures.
RAILWAY NOTES.
A narrow-gauge railroad has been proposed
in Guatemala, and agents are now in San
Francisco for the purpose of interesting capital-
ists in the scheme. It is understood that a
section of thirty miles, to penetrate the coffee
region, will be first made, and, if successful,
the road will be extended to the capital of the
State. Should the necessary capital be secured
in San Francisco, it is claimed that the trade of
Guatemala will be attracted to that city. If
the necessary aid cannot be secured there, an
appeal will be made to the capitalists of the
East or of Europe.
Of all the sources of railway disasters, shunt-
ing operations are perhaps the most prolific ;
but this truth has either failed of appreciation
by railway directors, or satisfactory means of
removing the danger have not appeared.
Among other inventors who have attempted
this, however, Mr. Barrow, of Rock Ferry,
Liverpool, has recently finished an apparatus
for the protection of sidings during shunting
operations. The signal consists of a revolving
signal and lamp fixed in the six-footway, 2 ft.
high, some 500 and 800 yards from the point,
and worked by the points-man in the signal-
box. The lever or wheel which works the
light also manipulates a couple of fog signals.
When the light is turned against a coming
train the fog signals are placed on the line by
mechanical means, so that should the driver
miss seeing the light, the fog signals warn him
in time to avert disaster.
Great activity is just now being shown in the
Austro-Hungarian Empire in the prosecu-
tion of all kinds of public works, and especially
of those in any way relating to the extension of
the railway system of the country. Amongst
others, there is a talk of the construction of an
iron bridge over the Drave at Eszeg, to replace
the present ferry, at a cost of 800,000 fls., which
would be carried out partly by the Government
and partly bv the Alfoeld and Fiume Railway
Company, which is domiciled at Pesth. It is
also proposed to replace by iron bridges all the
wooden bridges on the line worked by the
Alfoeld and Fiume Railway CompaDy, and the
Kaschau and Oderberg Railway Company, &c,
and the construction of the proposed lines of
railway on the military borders of Croatia and
Slavonia is to be offered for public auction —
in fact, according to Herapatli, one line has al-
ready been adjudged.
The supplement to the last Gazette of India
contains some interesting statistics of the
number of servants of all races employed on
the different railway lines in India. The grand
total foi-
l's miles of line is 132,040, or be-
tween eight and nine individuals per mile. Of
these 132,040 persons, 125,040 are natives, 3,319
are Eurasians — children of Europeans but born
in Asia — and 3,607 are Europeans. Again, of
the total number 8,837, of whom 8,257 are
natives, 271 Eurasians, and 309 Europeans are
employed in the department of general admin-
istration; 31,616, of whom 29 339 are natives,
1,233 Eurasians, and 1,044 Europeans in the
traffic and telegraph departments; 52,259, of
whom 51,631 are natives, 248 Eurasians, and
380 Europeans in the engineer's department ;
and 39,328, of whom 35,787 are natives, 1,567
Eurasians, and 1,874 Europeans, in the locomo-
tive and carriage departments. The first thing
that strikes us about these figures is the enor-
mously large proportion of natives, not only in
the total, but in every individual branch of the
work. In fact, it may almost be said that the
working of the railways is practically in the
hands of the natives of the country — in some
cases, but not in all, under European super-
vision. The insignificant number of Eurasians
employed is hardly less striking. In one de-
partment alone — traffic and telegraph — does it
exceed that of the Europeans. Turning again
to the statistics ' of casualties, we find that
among an average number of 3,513 Europeans
employed in the year ending 30th September,
1877, there were only eighty-three deaths, while
among an average number of 3,319 Eurasians
employed there were only thirty-nine deaths,
giving about half as high a death rate for
Eurasians as for Europeans. The dismissals
were 289 and 256 respectively, showing no
great disparity between the two classes.
474
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Railway Accidents. — The Annates des
Ponts-et- Chaussees has just published some
interesting statistics on the above named sub-
ject. In the old days of diligences, or stage-
coaches, one passenger was killed out of about
335,000, and one wounded out of 30,000 ;
while out of 1,784,404,687 persons carried by
the French railways from September 7th, 1835,
to December 31st, 1875, only one was killed
out of 5,178,490, and one injured out of
580,450. If the accidents are divided into two
groups, from September, 1835, to December,
1855, and from January, 1856, to December,
1875, we find that in the first period one trav-
eler was killed out of 1,955,555, and one
injured in 496,555. In the second, the propor-
tions were one killed out of 6,171,117 passen-
gers, and one injured in 590,185. As is seen,
the number had considerably decreased in the
second period. Of late years, the proportion has
still further diminished, and the results for such
countries as France, England, and Belgium are
particularly striking. In France, during the
years 1872, 1873, 1874, and 1875, one passenger
was killed out of 45,258,270, and one hurt in
1,024,360. In England, from 1872, to 1875, one
was killed out of 12,000,000 persons carried,
and one wounded in 366,000. In Belgium,
from 1872, to 1876, one was killed out of
20,000,000 passengers, and one injured in
3,500,000. To sum up, a person had, in
France, in the time of the diligences, a chance
of being killed in making 300,000 journeys,
and of being hurt once in making 30,000. On
the railways, from 1872 to 1875, the chances
were reduced to one death in 45,000,000
journeys, and one injury in 1,000,000. Thus,
a person continually traveling by rail, at a
speed of 50 kilometers (f of a mile each) an
hour, would have had, during the three periods
above indicated, the following chances of
being killed : From 1835, to 1855, once in 321
years ; from 1855 to 1875, once in 1,014 years ;
and from 1872 to 1875, once in 7,450 years.
Queensland Railways. —The Queensland
Minister of Works has intimated that the
Queensland Government has no intention of
undertaking the construction of proposed
branch lines from Ipswich to Fassifern, in one
direction, and to Mount Esk in the other,
unless the residents in the districts to be bene-
fited by their construction contribute towards
the cost, which, we suppose, means that a
system of rating railway districts is in contem-
plation. The proposed branch line from Oxley
to Beenleigh, is one with regard to which con-
siderable pressure is likely to be brought to
bear upon the Government ; but a contention
has arisen in favor of a diversion of the route
so as to serve the settlers of the Upper Logan
and the Albert. The Colonial Sugar Refining
Company of Sydney are forming an establish-
ment on the Tweed river, immediately south
of the Queensland Border, for the production
of sugar on an extensive scale. They have
purchased 10,000 acres of land, intending in
the first instance to grow their own cane, in
the expectation, however, that as soon as
machinery has been erected for crushing and
refining purposes, farmers will settle in the
neighborhood, and enable the company to
adopt the plan which they have found emi-
nently successful on the Clarence river, where
they last year exported about 7,000 tons of
sugar, none of which was from cane of their
own growing. But the Tweed is difficult of
navigation, and the company have asked the
Queensland Government to construct a short
line of railway or tramway from the Border to
Nerang Creek, Queensland, with the view of
making that the port for the produce of the
Tweed district, The company further ask
whether, in the event of the government
declining to undertake the work, they will per-
mit the company to make the line, and, if so,
upon what terms. The length of line will not
exceed 15 miles.
ENGINEERING STRUCTURES.
The work of tunneling the St. Gothard Rail-
way is being pushed on with considerable
rapidity. A telegram from Geneva states that
on the Goeschenen side alone 1,000 men are
employed inside the tunnel and 400 outside.
Three hundred wagon loads of earth are exca-
vated every day, and in the daily blastings 600
lbs. of dynamite are used. Equal energy is
being shown on the Italian side.
The Altenburg Tunnel. — H. Von Oer gives
a full and detailed account of the system of
supports, adopted at the Altenburg tunnel,
where iron was made use of in place of the
usual timbering. The system, as there carried
out, is due to Herr F. Rziha, an Austrian en-
gineer, and is a modification of that in use in
the Saxon mines for the timbering of drifts.
The author claims that it possesses all the ad-
vantages of the English system, as designed by
Brunei, without its defects. It consists essen-
tially in the adoption of the arched form, em-
bracing the whole section of the tunnel, the
structure being built up of short segments,
varying in length from 1 metre to 1| metre (3.28
to 4.9 feet), composed of angle iron, and joined
togeiher by the flanges. A characteristic fea-
ture of the system lies in the application of the
common forms of angle iron, by which means
economy in the cost of the materials is secured.
Herr Rziha makes large use indeed of old rails;
and the paper gives a drawing showing the
arrangement of these materials. The construc-
tion is a kind of double arch, the outer ring of
which supports the earth, and itself rests upon
the inner ring, which is designed to serve as
the centering upon which the masonry is to be
built in. As the work of excavation advances,
the outer ring supporting the rock is removed
in small portions at a time, and the bricking is
built up upon the lower ring. The distance
between the two rings being made to corre-
spond to the required thickness of the arch.
The several parts of the structure are simple in
form, light, "and easily put together. The erec-
tion is carried on, as the excavation progresses,
in a manner similar to that followed in the or-
dinary method of timbering. The system is
said to be a very efficient one, and a tabular
statement of quantities and cost shows it to be
also remarkably cheap. In one case, the econ-
ORDNANCE AND NAVAL.
475
omy resulting from the adoption of iron instead
of wood, amounted to as much as 84 marks per
lineal yard, the estimates being 328 and 412
marks respectively. The article is illustrated
by general and detail drawings, which show
clearly the design and mode of construction
adopted at the Altenburg tunnel. The same
system, the author remarks, is at the present
time being made use of in the Remsfeld tunnel,
900 metres (984 yards) in length, on the line of
railway from Berlin to Coblenz. — Abstracts of
Institution of Civil Engineers.
ORDNANCE AND NAVAL.
Steam Steering Gear. — One of our corre-
spondents in Lancashire writes: — "A new
steam steering gear, patented by Mr. Harrison,
was on Wednesday exhibited for the first time
at the works of Messrs. Hodgson and Stead,
engineers, Salford. By this invention Mr.
Harrison claims to secure to the helmsman a
perfect control over the steering engines, and
also to do away with the noise which is so
objectionable in the apparatus now in use on
some of the steamships. The first object is
attained by means of a rotary disc valve oper-
ated upon by the steering wheel, which cuts
off the steam automatically and controls the
action of the piston rod to within \ inch, the
engine, in fact, responding instantaneously to
every motion of the steering wheel, whilst the
noise is obviated by the substitution in the
working gear of a worm in the place of the
usual wheels and pinions. It is also claimed
that the engine will exert the power of twelve
men on the rudder, which will be kept steady
however rough the action of the sea may be
upon it. The working of the apparatus ap-
peared to give satisfaction to a number of
gentlemen who inspected it, but I understand
it is shortly to undergo a practical test on board
ship at Liverpool.
Russian Fast Sailing Steamers.— The
Moscow Cruiser Committee has definitely
decided that, if possible, no more war steamers
for the volunteer fleet are to be purchased out
of Russia The question was raised at a recent
sitting of the executive branch of the com-
mittee at St. Petersburg, under the presidency
of Mr. Pobairdonositz, and after the plaDS and
tenders received from shipbuilders and ship-
owners in every part of the world had been
carefully examined, the members unanimously
decided that an attempt should be made to en-
courage the shipbuilding trade of Russia by
giving all future orders to native firms. There-
upon Mr. Baird, of Baird's Engineering Works,
and, Mr. Kazi, the managing director of the
Baltic Iron Works, who "were both present,
undertook to furnish plans of fast-sailing
steamers. A temporary contract was drawn
up, the main features of which were that the
cruisers designed should be corvette shaped,
with a spread of 21,000 square feet of canvas,
stowage for sufficient coal to enable the vessel
to steam sixty days at full speed, and artillery
arrangements for the reception of two seven-
inch guns and four four- inch mortars. It was
understood that in the event of the designs be-
ng satisfactory Messrs. Baird and the Baltic
Ironworks would each receive an order for at
least one cruiser, and that if the donations con-
tinued to come in as largely as at present
further orders would be given.
The Hecla; Torpedo Depot Ship. — The
1 Hecla, screw torpedo depot ship, which ar-
rived at Portsmouth last week from Belfast,
and which is expected to be commissioned to-
day by Captain Morgan Singer, lately in com-
mand of the Vesuvius and the Glatton, is alto-
gether a novelty, no other ship of the kind
being in existence, and is another concession to
the necessities of the new mode of conducting
actions at sea. She is to be fitted to carry fast
torpedo launches and to follow in the wake of
a fleet as a depot, ready to despatch her flotilla
of small craft for their protection when neces-
sary. She is constructed of iron, and measures
390 ft. in length, and is fitted to carry six 64-
pounder muzzle-loading rifled guns, four on
the broadside and the rest forward and aft.
She is also intended to be armed with torpedoes
of the Whitehead kind, and is pierced with a
broadside port on each side for ejecting them.
, The after part below is furnished with lathes
| and drilling and shaping machines, and will be
! converted into a floating torpedo workshop.
She is divided into a number of various water-
tight compartments, not connected, as is the
usual mode, with water-tight doors, entrance
being gained from the upper and main decks.
The element of danger resulting from leaving
the connections open in certain eventualities is
thus obviated, though it is calculated that the
filling of one or two of the compartments with
water would not materially affect the behavior
of the ship. She is to carry six second class
torpedo boats, of which, however, only two
have as yet been supplied. Four of these boats
will be amidships, the chocks on which they
rest running on a tramway. She will also
carry a 42 ft. steam launch and a 87 ft steam
pinnace. The Hecla wili be provided with
booms and nets to protect her from an enemy's
torpedoes, the booms, when not in use, lying
fore and aft against the side of the ship. The
captain's cabin and the wardroom are amid-
ships, the wardroom being what, when the ship
was built for the merchant service, was in-
tended as a saloon for passengers. She will
have a complement of 170 officers and men,
and when completed at Portsmouth will be
taken to sea for a short period on special ser-
vice;f or the purpose of testing her manceuvering
and sea qualities. — London Times.
STEERING OF SCREW STEAMERS. — The fol-
lowing is the report of the Committee of
the British Association, consisting of James R.
Napier, F.R.S., Sir W. Thomson, F.R.S., W.
R. Froude, F.R.S., J. T. Bottomley, and Os-
borne Reynolds, F.R. S., Sec, appointed to in-
vestigate the effect of propellers on the steering
of vessels.
It appears, both from the experiments made
by the committee and from other evidence, that
the distance required by a screw steamer to
bring herself to rest from full speed by the re-
versal of her screw is independent, or nearly
so, of the power of the engines; but depends
476
VAN NOSTKAND'S ENGINEERING MAGAZINE.
on the size and build of the ship, and generally
lies between four and six times the ship's
length. It is to be borne in mind that it is to
the behavior of the ship during this interval
that the following remarks apply : —
The main point the committee have had in
view has been to ascertain how far the revers-
ing of the screw, in order to stop a ship, did
or did not interfere with the action of the rud-
der during the interval of stopping, and it is as
regards this point that the most important light
has been thrown on the question of handling
ships. It is found an invariable rule that, dur-
ing the interval in which a ship is stopping
herself by the*reversal of her screw, the rudder
produces none of its usual effects to turn the
ship, but that, under these circumstances, the
effect of the rudder, such as it is, is to turn the
ship in the opposite direction from that in
which she would turn if the screw were going
ahead. The magnitude of this reverse effect
of the rudder is always feeble, and is different
for different ships, and even for the same ship
under different conditions of loading.
It also appears from the trials that owing to
the feeble influence of the rudder over the ship
during the interval in which she is stopping,
she is at the mercy of any other influences that
may act upon her. Thus the wind which al-
ways exerts an influence to turn the stem (or
forward end) of the ship into ihe wind, but
which influence is usually well under the con-
trol of the rudder, may when the screw is re-
versed become paramount and cause the ship
to turn in a direction the very opposite of that
which is desired. Also, the reversed screw
will exercise an influence, which increases as
the ship's way is diminished, to turn the ship
to starboard or port according as it is right
or left handed; this being particularly the case
when the ships are in light draught.
These several influences, the reversed effect
of the rudder, the effect of the wind, and the
action of the screw, will determine the course
the ship takes during the interval of stopping.
They may balance, in which case the ship will
go straight on, or any one of three may pre-
dominate, and determine the course of the
ship.
The utmost effect of these influences when
they all act in conjunction, as when the screw
is right handed, the helm starboarded, and the
wind on the starboard side, is small as com-
pared with the influence of the rudder as it acts
when the ship is steaming ahead. la no in-
stance has a ship tried by the committee been
able to turn with the screw reversed on a circle
of less than double the radius of that on which
she would turn when steaming, ahead. So that
even if those in charge could govern the direc-
tion in which the ship will turn while stopping,
she turns but slowly, whereas, in point of fact,
those in charge have little or no control over
this direction, and, unless they are exception-
ally well acquainted with their ship, they will
be unable even to predict the direction.
It is easy to see, therefore, that if on ap-
proaching danger the screw be reversed, all
idea of turning the ship out of the way of dan-
ger must be abandoned. She may turn a little,
and those in charge may know in what direc-
tion she will turn, or may even, by using the
rudder in an adverse manner, be able to influ-
ence this direction, but the amount of turning
must be small and the direction very uncertain.
The question, therefore, as to the advisability
of reversing the screw is simply a question as
to whether the danger may be better avoided
by stopping or by turning. A ship cannot do
both with any certainty.
Which of these two courses is the better to
follow must depend on the particular circum-
stances of each particular case; but the follow-
ing considerations would appear to show that
when the helm is under sufficient command
there can seldom be any doubt.
A screw steamship when at full speed requires
five lengths, more or less, in which to stop her-
self ; whereas, by using her rudder, and steam-
ing on at full speed ahead, she should be able
to turn herself through a quadrant without
having advanced five lengths in her original
direction. That is to say, a ship can turn a
circle of not greater radius than four lengths,
more or less (see Hankow, Valetta, Barge) so
that if running at full speed directly on to a
straight coast, she should be able to save her-
self by steaming on ahead and using her rud-
der after she is too near to save herself by
stopping ; and any obliquity in the direction of
approach or any limit to the breadth of the
object ahead is all to the advantage of turning,
but not at all to the advantage of stopping.
There is one consideration, however, with
regard to the question of stopping or turning,
which must, according to the present custom,
often have weight, although there can be but
one opinion as to the viciousness of this cus-
tom. This consideration is the utter inability
of the officers in charge to make any rapid use
of their rudder so long as their engines are
kept on ahead. It is no uncommon thing for
the largest ships to be steered by as few as two
men. And the mere fact of the wheel being
so arranged that two men have command of
the rudder, renders so many turns of the wheel
necessary to bring the rudder over that even
where ready help is at hand it takes a long
time to turn the wheel round and round so as
to put a large angle on the rudder.
The result is, that it is often one or two
minutes after the order is heard before there is
any large angle on the rudder, and of course,
under these circumstances, it is absurd to talk
of making use of the turning qualities of a
ship in case of emergency. The power avail-
able to turn the rudder should be proportional
to the tonnage of the vessel, and there is no
mechanical reason why the rudder of the
largest vessel should not be brought hard over
in less than 15 seconds from the time the order
is given. Had those in charge of steamships
efficient control over their rudders, it is prob-
able that much less would be heard of the re-
versing of the engines in cases of imminent
danger.
BOOK NOTICES.
Prang's Standard Alphabets.
Prang & Co. Price $5.00.
D. Van Nostrand.
Boston: L.
For sale by
BOOK NOTICES.
477
This collection of ornamental alphabets for
the use of decorators, designers and draughts-
men, is in excellent style.
We are glad to see that in the more florid
ornamenting, the letters" are yet plainly dis-
tinguishable, which was not the case in the
letter books of former years.
In addition to the alphabets, there are some
examples of topographical mapping in colors,
and the Coats of Arms of the States also in
colors. Altogether, it is an elegant and useful
volume.
Practical Treatise on Casting and
Founding. By N. E. Spretson. Lon-
don: E. & F. N. Spon. Price $7.00. For
sale by D. Van Nostrand.
This book is for the artisan only. It affords
a complete description of all the details of cast-
ing and founding, iron, steel, brass and bronze.
The illustrations alone cover eighty-four
full page plates of royal octavo size.
The work is divided into thirty chapters
Coal and Iron in all Countries of the
World. By J. Pechar. London : Simp-
kin, Marshall & Co. Price $2.00. For sale by
D. Van Nostrand.
This is largely statistical as the title implies.
It is compiled from the latest sources, and is
one of the reports made up from materials
furnished by the Paris Exposition.
The report deals with the character of the
coal and iron deposits, methods of working,
and amount of home consumption and export.
The introduction under the head of General
Remarks, discusses the causes of the great
A Practical Treatise on Casting and depression in trade, and adds more valuable
Founding. By N. E. Spretson. Lon- statistical infoimation regarding the railway
systems of the world.
A History of the Growth of the Steam
Engine. By Robert H. Thurston,
A.M., C.E. New York: D. Appleton & Co.
Price $ 2. 50. For sale by D. Van Nostrand.
This is the latest addition to the "Interna-
tional Scientific Series " of these enterprising
but, without enumerating these, the following , C^inle^^t^l^^t^e^tt
of the series by a large plurality of scientific
ing the matter of the book in their order:
Pig Iron; Furnaces and their Accessories; j ^a^t
Moulding and Casting: Foundries and their
Equipments; Steel, Brass, Bronze and Bell
Founding; Tables and Notes.
There are 400 pages of text, besides the
the plates mentioned above.
Van Nostrand's Science Series, No. 39.
A Hand Book of the Electromagnetic
Telegraph. By A. E
York: D.Van Nostrand. Price, boards, 50 cts. ;
cloth, 75 cts. ; half mor., $1.00.
Instruction books for students in telegraphy
have heretofore been encumbered with mate-
rial which was of little or no aid to the be-
ginner.
A small hand book of first principles has
been needed to prepare the learner for the pre-
liminary work as well as for the understanding
of the complete treatises upon this compara-
tively new branch of industry.
For a student may be well up in electricity
and magnetism of the schools and colleges, and
entirely unlearned, not only in the application
of the principles of these sciences, but of the
technical language of the telegraph room.
Mr. Loring is a practical telegrapher, and
has presented in the most concise form the
leading facts and formulas which are in con-
stant requisition in telegraphing.
Without being severely technical, or even
rigorously scientific, he enables the student to
make a good reconnaissance of this field of la-
bor, and affords him such hints as will enable
him to fill in his details of information from
the more complete sources.
The work is divided into parts as follows :
Part 1, Electricity and Magnetism; Part 2,
the Morse Telegraph; Part 3, Batteries; Part
4, Practical Telegraphy; Part 5, Construction
of Sines.
Appendix containing suggestions and exer-
cises for learners.
The illustrations are good, and are distrib-
uted throughout the text.
The preparation of such a history could not
have been assigned to better hands. Taste,
early education and professional training have
all tended to prepare the talented author for
this work, and his experience furthermore
as an instructor of young men has specially
fitted him to relate the story of the growth of
anumAuiwiu ! tllig great agent of civilization, so that the
v ' merest tyro can enjoy it, and the scientist re-
gard it as valuable.
Not a small portion of the labor and expense
of the work, either to author or publisher, is
represented by the illustrations, which are very
numerous and exceedingly good.
The book is sure of a multitude of readers.
The Analytical Theory of Heat. By
Joseph Fourier. Translated by Alex-
ander Freeman, M.A. Cambridge: Univer-
sity Press. Price $7.00. For sale by D. Van
IS ostrand.
One of those works involving the higher
analyses to an extent that is specially attractive
to the mathematician.
When great laws of phyics and their result-
ant phenomena are expressed by aid of triple
integrals, the mathematician first feels an inter-
est in them, and then only proposes to aid in
the work of developing.
The department of Heat has long since be-
come a favorite field for the analyst, and the
work before us is the most complete evidence
of it.
The topics treated by chapters are :
1. Introductory ; Equation of the Movement
of Heat ; Propagation of Heat in an Infinite
Rectangular Solid ; Linear and Varied Move-
ment of Heat in a Ring ; Propagation of Heat
in a Solid Sphere ; Movement of Heat in a Solid
Cylinder ; Propagation of Heat in a Rectangu-
lar Prism ; Movement of Heat in a Solid Cube ;
The Diffusion of Heat.
It is a well printed volume of 466 pages,
royal octavo.
478
VAN NOSTRAND7 S ENGINEERING MAGAZINE.
GEOGRAPHICAL SURVEYING. By FRANK
de Yeaux Carpenter. New York: D.
Van Nostrand. Price 50 cts.
This little treatise, written originally, as it
appears, for the purpose of presenting to the
Geological Commission of Brazil a general
sketch of the plan proposed for mapping the
immense territory of that Empire, in connec-
tion with the Geological Survey organized by
the late Prof. Hartt, appears in Van Nostrand's
excellent Science Series, and forms a useful
contribution to the popular science literature
of our country. Its author, formerly connect-
ed with the geographical surveys of the
Engineer Department under Lieut. Wheeler,
proposes the name Geographical rather than
Topographical Surveying, to distinguish the
kind of work necessary for covering a large
extent of comparatively unexplored country
(when thousands of square miles must be map-
ped in a season) from the slow and detailed
surveying which indicates every man's farm
and house, as carried on by the Government
surveys of Europe. While the former should
be based on determinations of primary points
no less accurate than the latter, the intermedi-
ate details are to be sketched in by methods of
approximation, which will present with suffi-
cient accuracy the general physical features of
the region surveyed, and the method may
therefore be called ^-graphical rather than
&?£><9-graphical, as describing the surface of the
globe, rather than of limited regions or places.
This has been the system pursued by our
various Government geological surveys in the
Rocky Mountain region; and the author men-
tions the work of Hayden's, Powell's and
Wheeler's surveys, from whose experience he
has drawn his material, but neglects to give
credit to the forerunner and, in one sense, the
originator of all these, that of the 40th Parallel
under Mr. Clarence King. As he avoids all
formulas, and presents his subject with clear-
ness and precision, the work will be found
pleasant reading for all interested in geogra-
phy,— The Nation.
The Elements of Graphical Statics and
their Applications to Framed Struc-
tures, with Numerous Practical Ex-
amples op Cranes, Bridge, Roof and Sus-
pension Trusses, etc. By A. Jay DuBois,
C.E., Ph.D. New York. 1875. John Wiley
& Son.
In the course of a review of DuBois'
"Graphical Statics," published in the Zeits-
chrift des Ver, Deutsch Ing, the writer says :
" This surprisingly long title is followed by
a preface of ten closely-printed pages, which
contains notices valuable to the student while
using the book. The table of contents, of
twelve pages of fine print, is preceded by a
four-page note, ' Elements of Graphic Statics, '
intended especially for student and teacher.
Then follows, under the title 'Introduction,'
an excellent and exact translation ( !), including
references, of the capital work of our German
colleague, Dr. J. Weyrauch, ' Ueber die Oraph-
ische Statik? Leipsig : Verlag wn Teubner. The
title of the first chapter, ' Historical and Criti-
cal,' is accompanied by an asterisk with the
reference 'Weyrauch, U. S. W.'; and in his
preface DuBois says : ' For the historical and
critical introduction we are indebted, a few
alterations excepted, to the pen of Weyrauch.
It will be useful, &c., &c.' As regards the
' few alterations' of DuBois, we have not been
able to discover them, except in the omission
of several scientific references of Weyrauch.
The American reader is led to infer from Du-
Bois' method of reference that only one page
of his ' Introduction ' is taken from Weyrauch ;
when, in fact, as I find after a thorough exam-
ination, there are twenty-seven pages of close
translation.*
" What particular use was made of Culmann,
Mohr, Ritter, Winkler and Reuleaux, and how
much Cremona, Favaro and others were stu-
died, after the entire literature had been col-
lated by Weyrauch's diligence for the benefit
of the translator, we shall not determine: but
to DuBois belongs the credit of industry in col-
lecting, and of the introduction of practical ex-
amples.''
The reviewer then speaks favorably of the
work as a record of the progress of research
in this department in Germany, Italy, France
and England. Concerning the plates, he says:
"Entire plates show a lack of the care in de-
lineation which is required in a work like this.''
A Handbook of Patent Law of All Coun-
tries. By William P. Thompson, C.E.
London : Stevens & Sons ; New York : Van
Nostrand, 1878.
The author of this little book is the head of
a patent agency in Liverpool, and therefore
writes with the advantage of practical experi-
ence. The book has no pretension to be re-
garded as a complete treatise on patent law ; it
is rather a guide to patentees, and in many re-
spects an aide memoire to practitioners. The
first part is naturally devoted to a summary of
the English law, in which the progressive steps,
with their cost, towards the completed patent,
are clearly explained. The suggestions and
observations of the author, as for instance those
under the head of preliminary " Searches," are
generally practical, but there are a few slips
which should be corrected in a subsequent
edition. At the outset his statement of the
principle of our patent law as "a simple con-
tract between the Crown, on behalf of the
nation at large, and the inventor," is not legally
correct. This view of the relationship of
Crown and inventor was judicially repudiated
in the celebrated action of Feathers, vs. the
Queen, in which Cockburn, C.J., speaking for
the Court, explained the grant of a patent to be
a mere act of the prerogative, coupled with a
condition, namely, full publication by the
patentee. Again, Mr. Thompson says of joint
patentees that ' ' each can grant licenses inde-
pendently of the other," omitting to point out
that it is by no means clear that the royalties
will not belong to both. The well-known case
of Mathers vs. Green decided that a joint
patentee could work the whole invention for
his own benefit without accounting to his fel-
* In the same way Reye, Geometrie der Lage, and
Bauschinger, Graphische Statik, are employed ; of course
with references.
MISCELLANEOUS.
low-patentee ; but that decision expressly left
open the case of profits to be derived from the
grant of licenses. Under the head of "In-
fringements," Mr. Thompson writes thus :
"Patent trials are proverbially expensive in
England, the law and procedure being appar-
ently framed with the special object rather of
putting fees into the lawyers' pockets than of
doing justice promptly and cheaply. As the
cases have to be fought out by lawyers, almost
invariably utterly ignorant of the technicalities
of the case, and before judges, learned only in
the law, the probability of obtaining justice,
even with a long purse, is not extravagantly
great. Often, too, when the case comes to a
hearing, and nearly all the expenses of the law-
suit have been incurred, the court, conscious of
its poor qualification for deciding scientific
and technical matters, persuades the parties to
put the matter to arbitration." We are sur-
prised to find any one with any pretence to ex-
perience • writing in this strain. Surely -Mr.
Thompson must know that the actual cost of
preparing pleadings and bringing the action to
issue is trifling to a degree compared with the
costs of witnesses and the collection of evi-
dence— costs unavoidable so long as novelty
and utility are essential to a patent. He might
as justly say that the law and precedure were
framed with the object of benefiting profes-
sional expert witnesses — one at least of whom,
by the way, well known for his ability, is act-
ually a patent agent. That our courts are in-
capable of dealing with technical cases is am-
ply disproved by the way in which the cele-
brated Plimpton skate was handled by Bench
and Bar in the many actions in which it was
involved. As for arbitration as a solution of an
infringement queston, we can only say that if
a party or his adviser is sufficiently foolish to
consent to such a course — and presumably Mr.
Thompson has met with, a case, we have not —
and so preclude himself from judicial assist-
ance, he has only himself to blame. No court
in this country declines, or can decline, to try
such an action, if properly presented for its
decision. Moreover, it is not the fact, as stated
further on, that the court rarely makes use of
its power to grant an interim or " preliminary"
injunction until the trial is decided. This is
true in the case of new and untried patents,
but where the validity of a patent has been es-
tablished in another action, such an injunction
is almost of course. A great part of the book
is occupied by a very useful analysis of foreign
laws. So far as we have tested this digest it is
clear and correct. We would, however, sug-
gest a few additions. In every case the date,
or other reference, to the particular law should
be given, and the Government taxes should be
inserted. This latter is not always done in the
book before us, though it is true Mr. Thomp
son gives invariably the approximate cost of
obtaining the patent — including therein the
agent's fees of course. Moreover, it should be
stated with more precision whether preliminary
examination is or is not rejuirecL Such in-
formation for instance, is wanting here under
the head of "Belgium." The work concludes
with "Hints for Inventors," "How to Sell a
Patent," and some well-merited strictures on a
certain class of "Patent Agents." The defects
we have indicated do not seriously affect the
utility of the book. It contains a good deal of
information in a small space, and will be found
useful by a large section of our readers.— The
Engineer.
MISCELLANEOUS.
Height of Jets.— J. F. Flagg, C. E., gives,
in a communication to Engineering News
a new formula for jets of water.
It is
h=R—. 00127 H2
H being the head of water, and h the height of
the jet.
Glass-cloth.— Gastach, or glass-cloth, is a
name given by Dr. Hirzel, of Leipsic, to a
gas and water-tight stuff, which; he has re-
cently patented. This is produced by placing
a large smooth piece of so-called gutta-percha
paper between two pieces of some not too
coarse and dense material— e.g., shirting (un-
dressed),—and then passing the arrangement
between heated rollers. The outer pieces of
the shirting combine in the most intimate way '
with the enclosed gutta percha to form a ma-
terial which is impenetrable by gas and water.
It may be made still denser and more resistant
by being coated on both sides with, e.g., copal
lac. The material is said to be well adapted to
form gas-tight membranes for regulators of
pressure of compressed gas-bags, or sacks for
dry gas-meters, as also dry gas-reservoirs.
A New Method op Determining the
Heat Value op Fuel.— With regard to
the important question of the heat value of
fuel, it has been proved that conclusions from
the results of elementary analysis are very un-
certain, and, also, that little reliance can be
placed on direct evaporation experiments. In
a recent paper in Die Chemische Industrie, Dr
Weyl points out the faults of these methods
and recommends, as preferable, decomposition
of the fuel by dry distillation and analytical
determination of the solid, liquid, and gaseous
products of decomposition. In this method
the accident of too small a sample being used
is avoided, as also too great pulverization and
drying at high temperature and the decompos-
ing action of atmospheric oxygen, which is
therewith connected, and the whole of the coke
is weighed, and its carbon, hydrogen, and
mineral constituents determined. The water,
tar, and gas that are formed are measured, and
their hem of combustion ascertained with the
aid of data that have been supplied by Favre
and Silbermann and Deville. The final result
will, of course, exceed the true combustion
value of the coal by the amount of heat equiv-
alent to the work of decomposition into coke,
tar, and gas. The decomposition of the coal
should be done as quickly as possible, and at a
high temperature.
nONPIRMlTION OF THE DISCOVERY OF THE
\J Planet Vulcan.— In a communication
addressed to Rear-Admiral Rogers, foupt. of
the U. S. Naval Observatory, under the date of
August 2nd, Prof. J. C. Watson, of Ann Arbor
480
VAN nostrand's engineering magazine.
confirms his reported discovery of the interior
planet, to which we alluded in last week's
issue, in discussing the successful results of the
late eclipse expeditions. The letter contains,
likewise, a summary of the observations upon
which the announcement of the discovery is
based, and which, coming from so accomplished
an astronomer as Prof. Watson, leave no
reasonable doubt as to their genuineness and
of the accuracy of his inferences.
With Mars' moons, and the long-sought-for
Vulcan, as the contribution of America to this
department of science within two years, our
astronomers have earned more than their share
of trinmphs. The letter is as follows :
'*' I have the honor to report that at the time
of totality I observed a star of the four-and-a-
half magnitude, in right ascension, 8 hours, 26
minutes declination, 18 degrees north, which
is, I feel convinced, an intra-mercurial planet.
I observed with a power of forty-live, and did
not have time to change the power so as to
enlarge the disk. There is no known star in
the position observed, and I did not see any
elongation such as ought to exist in the case of
a comet very near the sun. I will hereafter
report to you more fully in regard to the
observations made. The appearance of the
object observed was that of a ruddy star of the
four-and-a-half magnitude. The method which
I adopted prevents the possibility of error from
wrong circle readings ; besides, I had memor-
ized the Washington chart of the region, and
no such star was marked thereon. By com-
parison with the neighboring stars on Arge-
lander's scale, the magnitude of the planet
would be fifth, although my direct estimate
at the time of the observation was four and a
half, as stated." — Polytechnic Review.
New Fire Engines.— The Metropolitan Fire
Brigade have just added to the plant of
the new chief station, in the Southwark Bridge
road, two of the most improved form of light
steam fire-engines, specially suited for rapid
transmission to a fire. Thesa engines were
tested on the premises of the makers, (Messrs.
Shand, Mason & Co.), in the presence of
Captain Shaw and his officers. Various im-
provements have been introduced; by means
of those in the boiler, steam was raised from
cold water to 100 lbs. on the square inch in 6-J
minutes, this being an acceleration of time by
about three or four minutes as compared with
tlie engines previously in use — a most essential
point, considering the necessity of bringing a
jet of water to bear upon the fire in the short-
est possible time. The increasing "height to
which warehouses and public buildings are
now carried in London rendering it necessary
for increased pressure in the water jet, has
been met in these engines by an increased area
of steam cylinder as compared with the water
cylinder, while the difficulty of the man in
charge of the jet being able to shut it off entire-
ly to avoid unnecessary damage by water, or
from other causes, without the roundabout
way of sending a messenger to the engine,
which may be in another street, has been met
by the adoption of a patent self-acting apparat-
us by which the jet may be entirely closed at
the building on fire without interfering with or
stopping the working of the engine. This is
accomplished by a special hydraulic safety-
valve regulated by a spring balance, which
allows all excess of pressure to be relieved by
passing the water to the suction-pipe. The
first of this improved form of engine has been
sent by the makers to the Paris Exhibition.
IMPORTANCE OF GEOLOGICAL KNOWLEDGE TO
Engineers. — The value of at least an ele-
mentary knowledge of geology to the engi-
neer cannot be over estimated. It is applica-
ble in nearly every work upon which he may
be engaged. In the projection of earthworks,
tunnels, drainage, water supply and the selec-
tion of sites for any structure, success depends
largely upon geological considerations.
The" engineer should be familiar with the
laws governing rock deposition and metamorph-
ism ; he should know how rocks are frac-
tured; upheaved and faulted; he should know
the characteristics of such as enter his work,
and he should know their order of succession.
The stability of earthworks depends quite as
much upon the character of the underlying
rock as upon careful construction. A deep
cut may change a natural drainage, and serious
results might follow. The trickling of water
through a severed bed of marl or sand may
produce a serious earth slip. The dip of the
beds should be ascertained.
Railroad and canal embankments and cut-
tings could oftentimes be more wisely located
at a great saving of cost. True, circumstances
may compel their location at points not geo-
logically economical, but the engineer who
can foresee the evils that might follow from
such location, will best be enabled to prevent
disaster. Enormous expense has attended re-
pairs resulting from the ignorance or neglect
of such anticipation. More than $100,000
wrere required to remedy the slips in the Breval
cut (3000 ft. ), on the Paris & Cherbourg railway.
In tunneling, a knowledge of stratification
is absolutely necessary, for without it no true
estimate can be made. Even the genius and
skill which projected that ■ grand work, the
St. Gothard tunnel, have had their brilliancy
clouded by the blundering miscalculation of
its cost. Want of thorough geological inquiry
seems evident.
The engineer should know what probable rock
will be found at a certain depth, whether or
not water may be expected, and if so, under
what pressure.
The location of reservoirs should not be
determined by merely superficial observation.
The suitability of the underlying stratum
should be settled. The fact that certain rocks
allow water to pass freely through them, while
others are almost absolutely impermeable, is as
important in its application to rocks out of
sight as to those at the surface. Land slips
teach us this.
• More time might be expended economically
in the careful examination of the surface rock;
it might be permeable without seeming so ; it
might be connected with a permeable stratum
containing injurious soluble matter ; or there
might be a near limit to its retentive power.
A little attention in this direction might be as
profitable as good construction.
VAN NOSTRANDS
ECLECTIC
ENGINEERING MAGAZINE.
NO. CXX -DECEMBER, 1878 -VOL. XIX.
TRANSMISSION OF POWER BY COMPRESSED AIR,
By KOBERT ZAHNER, M. E.
Contributed to Van Nostrand's Magazine.
II.
CHAPTER IV.
The Thermodynamic Equations Ap-
plied to Permanent Gases.
I.
DETERMINATION OF THE SPECIFIC HEAT AT
CONSTANT VOLUME.
Forming, from eq. (3), the partial dif-
ferentials :
\dp)~ R'W~~R;
d?t
dp.dv
1
R*
and substituting in eqs. (20) and (21), we
have :
(c-c')=jR3
and
(22) gives, c'—c
pV
R :
1
{a + t)
R=.238-
(22)
(23)
96.0376
1389.6
= .169
which is the specific heat at constant vol-
ume for atmospheric air.
II.
INTERNAL HEAT.
Placing eqs. (12) and (15) equal to
each other and substituting the value of
c from (22), we have :
Vol. -XIX.— No. 6—31
according to eq. (11).
Integrating, and substituting for R its
value — we have,
u=c/r—u0
or u—u^—c'r (24)
which shows that the internal heat for
every degree of temperature is increased
by a quantity c' (.169), and the increase
of the internal heat of a gas passing from
0°C. to t°C. is always the same, what-
ever variations its pressure may have un-
dergone in this passage, the volume
having been kej)t constant.
III.
QUALITY OF HEAT SUPPLIED.
The partial differentials formed from
eq. (3) placed in (15) gives :
dQ
_c'vdp + cpdv
~ ~R~
(25)
which is integrable only when we have a
given relation between p and v.
1. At constant volume; make dv = o,
v being constant. Then
482
VAN NOSTRAND's ENGINEERING MAGAZINE.
Po
w ervdp_c'v(p—p0)
R
R
C(T-T0)
(25a)
which defines the specific heat at con-
stant volume.
2. At constant pressure; here dp=o,
and eq. (25) gives :
Q=2^M
R
(25b)
IV.
EXPANSION AT A CONSTANT TEMPERATURE.
To find the work done by a gas ex-
panding isothermally, (that is, the abso-
lute temperature is maintained at a con-
stant value), we must satisfy Boyle's
law and write :
pv =p0v0 — constant ;
hence pdv + vdp=o; or, vdp=— pdv.
Substituting this in (25),
_(c— c')pdv_l
dQ.
R
\pdv ;
Introducing^ from eq. (3),
1^, .dv
da=^R(a + t) — ,
J v ' v
and,
q=Ir(«+*)/° J=1r(«+*) log. v-.
1 V
= j*V. log- - (26.)
Let W=the work done; then
W=p0v0 log. V—. (26a.)
the ordinary form for permanent gases.
EXPANSION IN A PERFECTLY NON-CON-
DUCTING CYLINDER.
If a gas expand adiabatically, (i.e.,
without any passage of heat either into
the gas from without or out of the gas
into other substances) dQ=o in eq. (25),
and we have,
c'vdp + cpdv = o.
Writing for — its value r, and integrat-
ing, we have
* The logarithms, it is seen, are taken in the Naperian
By stem.
/p dp />v dv . p : v
— + r/ — '=loff. — +r log. — =o
PoP J v0 V & p0 & VQ
^ P , i VT
=log. ■=-+ log. -, =0
^ Po . »/
or, log.— =log. — X (— n=log. -£-
Po ^0 V
hence, pif =p0v0r = constant; (2*7)
an equation which expresses the varia-
tion of pressure as a function of volume
when the expansion or compression is
adiabatic.
The external work performed during
a finite expansion is denoted by
/V /*V fifty
pdv = J p^Qr—=pj),T
j v~r dv (27 a)
J,^,7 * ]_) =PqVq
Since no heat is received from withouts
the thermal equivalent of the work must
be estimated as internal heat. If, now,
r0 and r are the initial and final abso-
lute temperatures, the decrease in in-
ternal heat will be
«'K-r).
Hence we must have,
pvr
Eq. (27) gives =1 ; multiplying
pQv
both members by — 2-^r we have,
pv
Po
V
V
r—1
\v _(v \r~l_a + t _ r %
(30).
also,
V0 P A
f-=-, and
vr p0'
v \pj
hence,
\vl \pj a + t0 r0 v ;
Substituting in (28) the values of p0v0
Iv y—1
from (3) and ( — ) from (81) we ob-
tain :
TRANSMISSION OF POWER BY COMPRESSED AIR.
483
r— 1 ( \pj
i
(32)
V — 1
a form often used . = .2908.
r
VI.
•Variations in the temperature of a gas
during expansion or compression in a
perfectly non-conducting cylinder.
Placing the second members of p0v0=
R (o+0» r=-» and J=C~^r in eq* ^
we get :
which is thus interpreted :
The decrease in temperature (during
an expansion from v0 to v) is proportional
to the initial absolute temperature.
The already established relation,
ro \v J
expresses the final temperature as a
function of the volumes; and if we know
the initial and final pressures, the final
temperature is expressed as a function of
these pressures as follows :
CHAPTER V.
Thermodynamic Laws Applied to the
Action of Compressed Air.*
I
FUNDAMENTAL FORMULAS.
The four equations formulating the
law for the expansion and compression
of dry air, are, as we have established
them,
*L=Rto=£!!=J(c-c> (34a)
_— i
* The subject of this chapter is very ably treated by M.
Mallard, in the "Bulletin de la Societe de 1' industrie
minerale," tome xii, page 615, to whom the writer is
greatly indebted.
These expressions sum up the relations
existing between the pressure, volume
and absolute temperature of a weight of
air w compressed or expanded in a per-
fectly non-conducting cylinder.
p0, r0, and v0 have reference to the
initial state of the weight of air consid-
ered, p, r'and v corresponding to the
final state.
The following table is that of MM.
Mallard and Pernolet. It gives for con-
P
venient values of — the corresponding
Po
values of — , &c. The tabular differ-
ences facilitate interpolation.
(See Table on following page.)
II.
WORK SPENT IN COMPRESSING AIR.
The compressing-cylinder being sup-
posed perfectly non-conducting as to
heat, our machine may be called a
"Reversible Engine;" for by reversing
the process of compression under exact-
ly the same conditions, we get back the
exact amount of work spent in the com-
pression.
The net work necessary to compress a
weight of air w, taken from a reservoir
(as the atmosphere) in which the pres-
sure p0 is kept constant, and to force it
into another reservoir in which the pres-
sure is constantly pl9 is made up of the
following parts: —
1. The work of compression:
2. Diminished by the work due to the
pressure pQ of the first reservoir (the
atmosphere) ; this work is p0 vQi v0 being
the volume of weight w under pressure
p0 and at the temperature ta :
3. Increased by the work necessary to
force the compressed air into the receiv-
ing reservoir; this is given by the
expression px vl9 vx being the volume of
a weight of air w at the pressure p, and
temperature tx.
As no heat passes between the air and
external bodies, the thermal equivalent
of the work, according to the mechanical
theory of heat, is the difference between
the quantity of internal heat possessed
by the air at its entrance into the cylin-
der, and that possessed by it its exit.
The heat possessed by the air at its
entrance into the cylinder is,
we1rn:
484
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Table I.
JL.
r
1
1-^
V
V
_*
X
Po
r<
r
r
V
V
0
t
Num-
Differ-
Num-
Differ-
Num-
Num-
Differ-
Num-
Differ-
Num-
Differ-
bers.
ences.
bers.
ences.
bers.
bers.
ences.
bers.
ences.
bers.
ences.
1.2
1.0543
481
.9485
415
.0515
1.1382
1317
.8786
911
.793
78
1.4
1.1024
436
.9070
344
.0930
1.2699
1262
.7875
712
.695
53
1.6
1.1416
439
.8762
293
.1274
1.3961
1218
.7163
575
.642
39
1.8
1.1859
367 •
.8433
254
.1567
1.5179
1179
.6588
475
.603
32
2
1.2226
343
.8179
223
.1821
1.6358
1145
.6113
400
.571
25
2.2
1.2569
321
.7956
198
.2044
1.7503
1116
.5713
342
.546
22
2.4
1.2§90
303
.7758
178
.2242
1.8619
1088
.5371
297
.524
19
2.6
1.3193
187
.7580
161
.2420
1.9707
1065
.5074
260
.505
17
2.8
1.3480
272
.7419
147
.2581
2.0772
1043
.4814
230
.488
15
3
1.3752
260
.7272
124
.2728
2.1815
1023
.4584
205
.473
13
3.2
1.4012
248
.7138
125
.2862
2.2838
1005
.4379
185
.460
12
3.4
1.4260
238
.7013
116
.2987
2.8843
587
.4194
167
.448
10
3.6
1.4498
230
.6897
107
.3103
2.4830
972
.4027
151
.438
10
3.8
1.4728
220
.6790
100
.3210
2.5802
957
.3876
139
.428
9
4
1.4948
213
.6690
94
.3310
2.6759
943
.3737
127
.419
9
4.2
1.5161
206
.6596
89
.3404
2.7702
930
.3610
117
.410
8
4.4
1.5367
200
.6507
81
.3493
2.8632
118
.3493
111
.402
7
4.6
1.5567
193
.6424
79
.3576
2.9550
906
.3384
101
.395
7
4.8
1.5760
188
.6345
75
.3655
3.0456
896
.3283
93
.388
^6
5
1.5948
865
.6270
322
.3730
3.1352
4333
.3190
388
.382
27
6
1.6813
769
.5948
260
4052
3.5685
4129
.2802
290
.355
19
7
1.7582
694
.5684
217
.4512
3.9814
3858
.2512
227
.334
19
8
1.8276
636
.5471
183
.4529
4.3772
3817
.2285
184
.317
14
9
1.8712
588
.5288
159
.4712
4.7589
3697
.2101
151
.303
12
10
1.9500
544
.5128
141
.4871
5.1286
3583
.1950
126
.291
10
11
2.0044
512
.4988
124
.5012
5.4869
3484
.1824
111
.281
9
12
2.0556
484
.4864
111
.5136
5 8353
3430
.1713
95
.272
9
13
2.1040
457
.4753
101
.5247
6.1783
334
.1618
83
.263
7
14
2.1497
434
.4652
92
.5348
6.5123
3273
.1535
73
.256
6
15
2.1931
.4560
.5440
6.8396
.1462
.250
The internal heat at its exit is,
wcxrx.
Hence the work of compression is,
Jwc1 rx — Jwc1 r0 = Jwc1 (rx — r0) ,
and the net work is,
Substituting for pQv0 and p1v1 their
values from eq. (34a) we have,
W^Jwcfo-r,,) (35)
an equation perfectly general for dry
atmospheric air.
III.
WORK OBTAINABLE FROM THE COMPRESSED
AIR.
If, by any process, we cause a weight
of air w to pass from one reservoir, in
which there is a constant pressure p0.,
into another reservoir, in which there is
a constant pressure piy and thereby con-
sume an amount of work Wj, the same
weight of air w (supposing the air to
remain in the same physical conditions)
will restore the amount of consumed
work W, in passing back from the
second reservoir into the first. These
are the conditions of a perfect thermody-
namic engine.
The work theoretically obtainable
from compressed air is therefore, eq. (35),
W1=J^b(r1.-r6)
an equation which shows how important
it is to take into account the initial and
final temperature of the air.
IV.
THE THEORY OP COMPRESSION.
1. The work necessary and the volume
of the Compressing-Cylinder. Neglecting
TRANSMISSION OF POWER BY COMPRESSED AIR.
485
all dead spaces and resistances, we can
easily calculate, by the aid of our formu-
las and of table I, the work necessary to
compress to a pressure p1 a weight of air
w, taken at a pressure p0 and a tempera-
ture r0, as well as the volume to be given
to the cylinder of the compressor to
compress a given weight of air to per
second, the time T being given in
seconds.
Our formulas are :
W, = 3wc(rl — r0) = Jioct0
|,(35a)
when a final temperature Txy which is not
to be exceeded, is assumed, the value of
— being obtained as a function of —
J" , P°
from table 1 , or from an adiabatic curve.
when a pressure pl9 to which we wish to
attain, is assumed.
w.=^\4il|-4
(35c)
an equation employed when we wish to
find Wj as a function of the volume v0 of
the air instead of as a function of its
weight. This equation is obtained by
substituting in eq. (35a.) the value of r0
from eq. (34«.), and r for —.
c
Table II.
p±_
x
Final Temperature
Po
L\
in Degrees C.
2
358.2
85.2
3
402.9
129.9
4
437.9
164.9
5
467.2
194.2
6
492.6
219.6
7
515.1
242.1
8
535 4
262.4
9
554.1
281.1
10
571.3
298.3
11
587.2
314.2
12
602.2
329.2
13
616.4
343.4
14
629.8
356.8
15
642.5
369.5
From eq. (34a.) we have,
Y=R<
XT,
(36)
an equation for the volume of the cylin-
der which compresses per second a
weight of air w, when the time, T, re-
quired per single stroke of the com-
pressor (or per double stroke when the
compressor is single-acting), is given in
seconds.
2. The final temperature of the com-
pressed air. This is found by looking in
Table I. for the
values of — opposite
the different values
of£.
Supposing
the initial temperature r0 = 293° = 20°C.,
we find for the different values of — the
Po
values of r1 in degrees of absolute tem-
perature and degrees C, as follows :
THE THEORY OF TRANSMISSION.
1. Loss of Pressure due to Transmis-
sion.— The loss in pressure which results
from carrying compressed air from one
point to another point distant from the
first, is due,
1.° To the friction between the air and
the conveying pipes;
2.° To sudden contractions in the
pipes;
3.° To sharp turns and elbows.
From experiments made at the Mont
Cenis Tunnel, the loss of pressure from
friction in pipes was formulated thus: —
uH
AjP=.00936-r,
(3<)
where «=the velocity of the air per
second,
£=length of the pipes,
d= diameter " "
Hence the loss of pressure varies,
directly as the length of pipe; directly
as the square of the velocity of the air in
the pipe; inversely as the diameter of
the pipe.
If w be the weight of air required
by the working- cylinder per second,
3.1416 -u being the volume of air passing
through the pipe per second, and pt and
Tj being the pressure and absolute tem-
perature respectively of the air in the
reservoir, we have, from eq. (34«)
486
van nostrand's engineering magazine.
3.1416— up
Jw(c—cf);
Solving with respect to u and substitu-
ting in (37), we have,
Ai?=13.88— ^6
pl d
when Joule's equivalent is taken in
French units ; when taken in British
units (772 foot-pounds per British ther-
mal unit), we have,
~r 2,,. 2
(38)
r -w\
Ap = ±3.055^l
which expresses the loss of pressure due
to friction in the pipes as a function of
the weight of air supplied per second, of
the temperature and pressure of the air
in the reservoir, and of the length and
diameter of the pipe.
2. Difference of Level. — The difference
of level which exists between the reser-
voir and the compressor and the com-
pressed-air engine (as when the latter is
at the bottom of a mine) compensates in
part at least for the loss of pressure due
to the friction in the supply-pipes. The
gain in pressure due to this difference of
level is readily calculated by means of
the ordinary barometric formulae. (See
Wood's Elementary Mechanics, p. 327).
VI.
THE THEOKY OF COMPLETE-EXPANSIVE
WORKING.
1. Notation. — Let #0=the absolute
temperature of the compressed air when
it enters the working cylinder;
6^= the absolute temperature of the
air after expansion;
0o=the pressure of the compressed air
on entering the working-cylinder;
^^the pressure at the end of ex-
pansion.
2. Work theoretically obtainable. —
This is given in Chap. IV, Section III,
and is :
W^Jwcid-d^JwcS^ 1
0.
=jwceo\i-(fyr-r\
(39)
6
■^ being obtained from the formula for
the
3. Final Temperature. — This is given
by eq. (34c?) and is :
it can be calculated directly by the use
of Table I when we know — ', the ratio
of the final to the initial temperature.
4. Volume of the Working- Cylinder.
— The volume of the working-cylinder,
being the same as the final volume of the
air after expansion is, from eq. (34a),
V=Jwp(c-
(40.)
where w=t\\Q weight of air furnished per
second and T=the time in seconds of
one stroke.
5. Weight of Air required per Second.
This is determined by the work which is
to be done by the compressed-air engine
per second. Letting n be a certain co-
efficient embracing resistances of all
kinds, we have, Chap. IV, Section III.
"=*je(%-e,) _ (41)
Substituting this value of w in eq. (36)
we have, •
W„T r„ r-1
V ~JcX k(60
■0J
x— =
Po
WT
X
*(0.-0JXA' (42)
the volume of the compressor in order to
supply the given amount of air.
6. Cold resulting from Expansion. —
While in the compressor there is a great
development of heat from the compres-
sion of air, in the working-cylinder there
is a great fall of temperature »due to its
expansion. The final temperature 6X is
calculated from the formula of Chap. IV,
Sec. VI, 3.
6 . (p
The valves of *, corresponding to -1,
^0 T 0
and the reciprocals, are found from
Table I. The following table is from M.
Mallard: The initial absolute tempera-
ture is assumed ^0 = 293°, that is, 20° C.
This table shows what very low tem-
peratures are reached when we work full
expansion with air at a high pressure.
Ice is formed from the water-vapor
present in the air, and seriously interferes
with the action of the working engine.
TRANSMISSION OF POWER BY COMPRESSED AIR.
487
Table III.
*
Final Temperature.
+.
Absolute 0 .
Degrees C.
2
239.6
— 33.4
8
213.0
— 60.0
4
196.0
— 77.0
5
183.7
— 89.3
6
174.2
— 98.8
7
166.6
—106.4
8
160.3
—112.7
9
154.9
—118.1
10
150.1
—122.9
11
146.1
—126.9
12
142.5
—130.5
13
139.2
-133.8
14
136.3'
—136.7
15
133.6
—139.4
VII.
THE THEORY OF FULL PRESSURE WORK-
ING.
1. Work obtainable. — This is, in the
present case, expressed by the equation,
W2=V3(^-0,). (43)
Placing in this equation the value of V2
from eq. (40) we have,
W,=J«(c-oO0.|l-^. (44)
The general expression for the work
restored has been given by eq. (39),
where 6Z is the temperature of the air
after it has been exhausted and has as-
sumed the pressure of the atmosphere ip^
2. Filial Temperature. — Placing eqs.
(44) and (39) equal to each other,
6>
1 r
-HM-t)
-l 4\
<Pr
.7102 + . 29^ (45)
3. Weight of Air necessary per Sec-
ond.— This is given by eq. (41).
4. Volume of Cylinder. — Substituting
w, eq. (41), in eq. (34a), we have,
c—c
X
W2T
"■{-It'
(46.)
VIII.
THEORY OF INCOMPLETE EXPANSIVE
WORKING.
1. Work attainable. — This is given by
eq. (39).
2. Final Temperature. — We have, eq.
(34a),
6°
from which we get 6\ (the temperature
at the end of the stroke). 0, is then
found from the equation,
0, 1 r— 1 <p1
0'~r+'
3. Ihe weight of air used. — This is
given by eq. (41.)
4. Volume of the Cylinder. — Eq. (34a),
written to satisfy our conditions, be-
comes :
V=J(c-c')wT^,
^ i
or, substituting the value of w from eq.
(41),
r_l WT
v,= „;« n ,. (47)
' of*
IX.
GRAPHICAL REPRESENTATION FOR THE
ACTION OF COMPRESSED AIR.
Let abscissas, in diagram on next page,
be volumes and ordinates, pressures;
taking O for the origin. Through B
{Povo) construct an adiabatic curve from
its equation, (eq. 27).
" The intrinsic energy of a fluid is the
energy which it is capable of exerting
against a piston in changing from a given
state as to temperature and volume, to a
total privation of heat and indefinite ex-
pansion." The intrinsic of 1 lb. of air
at p0 and v0, will be represented by the
area included between the axis of
abscissas, the ordinate AB=/>0 (at a
distance from the origin OA=v0), and
the portion of the adiabatic curve ex-
tending indefinitely from B until it be-
comes tangent to the axis of abscissas
when a3=oo. The algebraic expression
for this area (found by integrating eq.
(27 a) between the limits oo and v0 is,
iJWjL
(47A)
^>0=mean pressure of atmosphere in
lbs. per square foot=2116.3;
v0= volume in cubic feet of 1 lb. of air
at pressure p0 and temperature ra
= 12.387;
488
VAN NOSTRAND'S
ENGINEERING
MAGAZINE
•
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j
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iff£
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s ; ' pi "
: Jj
r i r
—
r0=493.°2 corresponding to 32° F;
r= 1.408; hence
1=^7 = 64250 foot-pounds;
that is, one pound of air, at mean baro-
meter pressure and 32°F, possesses an
intrinsic energy of 64250 foot-pounds;
and it is upon this store of e?iergy that
we draw, when, after abstracting in the.
form of heat all the work we had ex-
pended in compressing the air, we yei
cause it to perform work by expansion.
Through B construct an isothermal
curve from its equation (eq. 1). At a
point (as L) chosen arbitrarily upon
this curve to correspond to a desired
pressure we can construct another adia-
batic curve LRN. Then will the rela-
tions exist, expressed in the following, as
given by Prof. Frazier :
Area ABDC prolonged indefinitely=
intrinsic energy possessed by the
air before compression = I.
Area ABLPA=the work performed in
compressing the air.
Area DBLRN prolonged indefinitely =
ABLPA= energy in the form of
heat abstracted by the cooling
water; consequently, BSND pro-
longed indefinitely=ASLPA.
Area CKRN prolonged indefinitely =
intrinsic energy of the air after
expansion.
Area KRLPK=work performed by
the air in its expansion.
Area ABRKA=work performed by
the air after it leaves the working-
cylinder.
Area DBRSN prolonged indefinitely =
ABRLPA=the heat absorbed
by the air after leaving the work-
ing - cylinder. For isothermal
compression, we have,
Area ABLHOA=total work perform-
ed in the compressing-cylinder.
Area ABLPA=work performed in the
compression of the air.
Area PLHOP=work performed in the
expulsion of the air from the com-
pressor.
Area ABUOA^work performed by
the atmosphere.
Area UBLHU= ABLPA=the work
performed by the motor.
Area 0TLHU= useful work performed
by the air (full pressure).
Area TJBLHU - UTLHU = TLBT=
amount of work lost.
For adiabatic compression we have :
Area ABXYA=work performed in
the compression of the air.
Area YXHOY=work performed in
the expulsion of the air from the
compressor.
Area ABU OA= work performed by
the atmosphere.
Area BXHUB=work performed by
the motor.
Area TLHUT= useful work performed
by the air (full pressure).
TRANSMISSION OF POWER BY COMPRESSED AIR.
489
Area BXLTB=BXHUB-TLHUT=:
amount of work lost.
When the air is allowed to expand
fully (to its original pressure jt?0),
Area RTLR= useful work of ex-
pansion.
Area UHLRU= total useful work (=
UTLHTJ + RTLR).
Area BXLRB= BXHUB- UHLRTJ
—amount of work lost where air
is cooled after leaving the com-
pressor.
Area BLRB = UBLHU-UHLRIT=
amount of work lost where air is
cooled completely in compressor.
The area BLRB represents, then, the
excess of work performed on the air
above that performed by it, or the
amount of work permanently transform-
ed into heat. It is, therefore, not possi-
ble, even by preventing any rise of tem-
perature during compression and allow-
ing the air to expand to its full extent,
to obtain from the compressed air as
much work as was expended in the com-
pression. We can obtain from com-
pressed air all the work expended upon
it, only by causing it to reproduce exact-
ly during its expansion the changes of
condition it underwent during compres-
sion. This may theoretically be accom-
plished in three ways.
1. By allowing the compressed air to
become heated during compression, and
preventing all transmission of heat until
it leaves the working cylinder. It will
be compressed and expand in this case,
following the curve BX.
2. By cooling the air during compres-
sion and heating it during its expansion,
in such a manner that its temperature,
shall remain constant during both opera-
tions. The air will be compressed and
expand in this -case, following the curve
BL. The heat abstracted during com-
pression will equal that supplied during
expansion.
3. By cooling the air before its com-
pression to such a degree that after it is
compressed it will have the temperature
of the media surrounding the working
cylinder. The air will be compressed
and expand in this case, following the
curve RL.
CHAPTER VI.
Efficiency Theoretically Attaina-
ble.
I.
EFFICIENCY OF THE AIR-COMPRESSOR AND
COMPRESSED-AIR ENGINE, AS A SYSTEM,
Work performed on the air
Work performed by the air
the efficiency =E;
hence,
E
_W,_Jc(0o-0>
6,
\k-'\
W1 Jc(rl — r0)w
X
m
■-5H
r— 1
P,V-
Po)
(48.)
(p p
In practice, -r and — differ very little
^i Pi
in value, their difference being due to
the loss of pressure from the friction be-
tween the air and the supply-pipe, a loss
which is very small if the pipes are of
sufficient diameter.
Hence we may write,
E =
0,
(48a)
that is to say, when compressed air is
made to expand completely, and when
the ratio of its pressure to the pressure
of the surrounding atmosphere is the
same when the air leaves the compressor
as when it enters the cylinder of the
compressed-air engine, the efficiency of
the system is the ratio of the tempera-
ture of the compressed air when it leaves
the compressed-air-engine cylinder to
the temperature of the air at its entrance
into the compressor.
This law is independent of any heat
lost by the air in passing from one cylin-
der to the other. v
Since we have just admitted that,
we have,
r—1
490
van nostrand's engineering magazine.
hence,
showing that the loss of work is propor-
tional to the loss of heat undergone by
the compressed air in its passage from
the compressor to the working-cylinder.
The efficiency will be a maximum
when 1^ = 0,; that is, when the loss of
heat is nothing. Of course, this con-
dition cannot be realized. Generally the
compressed air reaches the working
cylinder with a temperature equal to
that of the surrounding atmosphere.
The temperature #e is therefore given,
and the efficiency can only be increased
by diminishing xx.
The following table is calculated from
<eq. 486) for different values of — the
Po
temperature of the compressed air at
entering the working cylinder being
taken #0 = 293°, that is, 20° C.
Table IV.
£i
E.
Pi
E.
Po
Po
2
.82
9
.53
3
.72
10
.51
4
.67
11
.50
5
.63
12
.49
6
.60
13
.48
7
.57
14
.47
8
.55
15
.46
and as "Pv=pYt and Y=nv, we have
W
hence,
E:
The table shows that when the press-
ure has reached four atmospheres, even
a considerable increase of it does not
much effeqt the efficiency.
II.
MAXIMUM EFFICIENCY CALCULATED PROM
THE INDICATED WORK.
Let P=the pressure of the compressed
air,
Let p= the pressure of the atmosphere,
Y and v=the corresponding volumes;
W~pYx 2.303 com. log. ri
HI
also let P:
np
then Y=nv.
The work spent upon the air to com-
press it, is, (eq. 26),
V
W1 —p Y nap. log. — —yY x
2.303 com. log. n
The work performed by the air is :
2.303 com. log. n ^''
Substituting different values of n in
this formula we get the corresponding
values of E.
III.
THE EFFICIENCY OF COMPLETE EXPANSION
AND OF FULL PRESSURE COMPARED.
To show the comparative merits and
demerits of full pressure and complete
expansion in the use of compressed air,
we present a table prepared by M. Mal-
lard.
(See Table on following page.)
The initial temperature is assumed at
20°C.
The table shows that by working non-
expansively we avoid very low tempera-
tures of exhaust; but this is of little
practical importance when we take into
account the low efficiency of full pressure,
as compared with complete expansive
working. Also when working at full
pressure, the higher the working pressure
the lower the efficiency.
CHAPTER VII.
The Effects of Moisture, of the
Injection of Water, and of
the Conduction of Heat.
I.
GENERAL statements.
In dealing with compressed air we
must always keep in view the very im-
portant consideration of the initial and
Unal temperature of the air.
There are two principal causes tending
to vary the amount of heat present in
the compressor or absorbed in the work-
ing-cylinder:—
1. The water or water-vapor of which
atmospheric air always contains more or
less, and which is purposely introduced
TRANSMISSION OF POWER BY COMPRESSED AIR.
491
Table V.
^e
Final tempera-
Theoretical effi-
Final tempera-
Theoretical effi-
ciency with
full pressure.
Ratio of efficiency
ture. Degrees
ciency with
ture. Degrees
at full pressure to
#i
C. Complete
expansion.
complete expan-
sion.
C. Full press-
ure.
efficiency at com-
plete expansion.
2
— 33.4
.855
—22.4
.82
.95
3
— 60.0
.806
—36.9
.72
.90
4
— 77.0
.782
—43.2
.67
.86
0
— 89.0
.768
—48.0
.63
.82
6
- 98.0
.758
—51.0
.60
.79
7
—106.0
.751
—53.0
.57
.74
8
—112.7
.746
—54.5
.55
.73
9
—118.1
.742
—55.6
.53
.71
10
—122.9
.739
—56.5
.51
.69
11
—126.9
.736
—57.4
.50
.68
12
—130.5
.734
—58.0
.49
.66
13
—133.8
.732
—58.6
.48
.65
14
—136.7
.730
—59.2
.47
.64
15
—139.4
.729
—59.5
.46
.63
into the cylinder of the so-called wet-
compressors.
2. The conduction of heat by the
cylinders, supply-pipes, reservoirs, &c.
II.
THE EFFECTS OF MOISTURE.
Atmospheric air always contains more
or less moisture. We wish to consider
the effects of this moisture upon the air
undergoing compression or expansion.
The injection of water into the cylinders
and its cooling or heating effects are left
out of the question altogether, as they
will receive attention further on.
In all conditions of temperature and
pressure practically realizable, a mixture
of air and saturated water-vapor will
remain saturated when the mixture ex-
pands against a resistance, a certain
quantity of water being thereby con-
densed ; on the contrary, compression
superheats the vapor, which then
becomes non-saturated, and non-satu-
rated vapors follow the laws of perma-
nent gases.
1. Influence of icater-vapor upon the
work spent on the air and upon that
performed by it. — The presence of mois-
ture in the air has been found to be
favorable both in the compressor-cylin-
der and working - cylinder. In both
cases, however, the gain in work spent
or performed is so slight that it can be
entirely neglected, and the formulas
already established for dry air become
applicable with a sufficientlv close
approximation. In the case of com-
pression, the vapor is superheated and
therefore comports itself very much like
the air itself; while in the working-cyl-
inder, the increase of work performed,
when the initial temperature of the
compressed air does not exceed 30° C,
is very small; and, as the temperature at
which compressed ajr is used, is rarely
higher than 20° C, the influence of the
water- vapor can be safely neglected.
2. Influence of the moisture of the air
upon the Fined Temperature. — The pres-
ence of the moisture in the atmospheric
air introduced into the compressor tends
to lessen the heat of compression; this
effect, however, is very slight, and, in a
practical point of view, is not worth
considering.
When compressed air is completely
expanded in a working-cylinder, the
presence of moisture in it tends to lessen
the cold produced. M. Mallard has
found what the initial pressure would be
for certain initial temperatures, so that
the final temperature should not fall
below 0= C. He has found this for both
dry and saturated air, and his results are
tabulated as follows: —
{See 1 able on following page.')
This table shows that, if compressed
air at 50°C and at a pressure of three
atmospheres be introduced into a work-
ing-cylinder, this air, if saturated with
aqueous vapor, can be completely ex-
panded without falling to a temperature
below 0°C; and that this air, if dry, dare
492
VAN NOSTKAND'S ENGINEERING MAGAZINE.
Table VI.
Final tem-
perature.
Degrees C.
Initial tem-
perature.
Degrees C.
Value of ti with the
air.
Saturated
with water-
vapor.
Dry.
0°
0°
0°
0°
20°
30°
40*
50°
1.50
1.89
2.39
3.06
1.276
1.432
1.602
1.780
not exceed an initial pressure of 1.78
atmospheres if its 'final temperature is
not to fall below 0°C.
3. Volume of the Cylinders. — This is
calculated as for dry air, since the effect
of the moisture is too slight to be taken
into account.
III.
THE INJECTION OF WATER.
1. The Effect of Introducing Water
into the Compressor- Cylinder. — It is of
great advantage in practice to intro-
duce cold water into the compressor.
It carries away the heat of compression
toa very great extent. It acts as a lu-
bricant, and, by cooling the cylinder, it
prevents the destruction of any organic
material, such as packing, valves, &c,
that may be employed upon it.
If in addition to the atmospheric
moisture present in the air at its entrance
into the compressor, water be introduced
in quantities just sufficient to keep the
air saturated with water-vapor during
the compression, the work spent upon
the air and the final temperature at the
end of compression will both be less than
if the air had not been kept saturated
while being compressed. It is unneces-
sary to calculate the amount of work
saved or the extent of temperature re-
duced by the presence of this saturated
water- vapor; for if water is at all to be
introduced into the compressor, it may
as well be thrown in in larger quantities^
that is, in quantities sufficient to absorb
and to carry off the greater part of the
heat of compression.
The effects of the heated air in the
compressor is a great cause of loss of
motive power, and it is very desirable to
cool the air during its compression.
The final temperatures for different
pressures have already been given in
Table II. We repeat them here in con-
nection with the quantities of work
spent when the compression follows
Boyle's law and when it is effected with-
out any removal of heat.
Table VII.
GO
Compression with
Compression with increase of
Loss of work
Fraction of the
a t
temperature constant.
temperature
due to the
total work
required for
compression,
o P*
Volume
Work in
Tempera-
Volume in
Work in
pression.
in cubic
kilogram-
ture in
• cubic
kilogram-
kilogram-
which is con-
H %
meters.
meters.
Degrees C.
meters.
meters.
meters.
verted into heat.
1
1.00
20°
1.
2
.50
7,199
85°.5 .
.612
7,932
733
.092
3
.333
11,356
130°.4
' .459
13,360
2004
.150
4
.250
14,260
165°.6
.374
17,737
3477
.196
5
.200
16,580
195°.3
.320
21,209
4629
.213
6
.167
18,475
220°. 5
.281
24,310
5835
.240
7
.143
20,038
243°.2
.252
27,048
7040
.260
8
.125
21,422
263°. 6
.229
29,518
8096
.274
The Quantity of Water to he Injected.
— We have found eq. (26), that the
quantity of heat developed by compres-
sion is given by the formula,
Q=^nap.log.|^|,
where r0 is the absolute final temperature
= 273° + 40°=:313o. From this formula
the quantity of heat, Q, is calculated for
different pressures. We then find the
weight of water, which, if introduced at
20°C and removed when it has taken up
enough heat to raise its temperature to
40°C, would absorb this quantity of heat
Q. Under these conditions we find that
TRANSMISSION OF POWER BY COMPRESSED AIR.
493
each kilogramme of water will absorb 20
calorics. Dividing Q by 20 we get the
weight of water to be introduced in
kilogrammes. In this way the follow-
ing table was prepared :
Table VIII.
Weight of water at
Heat devel-
20° C. to be injected
Absolute
oped by com-
into the compressor
pressure to
pression and
per kilogramme of
which the
to be carried
air compressed in
air is com-
off by the
order to keep the
pressed.
injected
final temperature
water.
from rising above
40° C.
atmospheres.
calories.
kilogrammes.
2
14.695
.734
3
23.284
1.164
4
29.392
1.469
5
34.120
1.701
6
37.979
1 891
7
41.264
2.063
8
44.087
2.204
9
46.589
2.329
10
48.816
2.440
11
50.849
2.542
12
52.694
2.634
13
54.391
2 719
14
55.962
2.798
15
57.425
2.871
Engine. — In the production of compress-
ed air, the great cause of loss of motive
power, as we have seen, is the develop-
ment of heat. Analogous to this is the
loss which occurs in the use of compress-
ed air. Great cold is produced by-
expansive working, and this has long
forbidden its adoption. The injection
of hot water into the working-cylinder,
has now made it possible to attain the
desirable result of working expansively.
The Quantity of Hot Water to be
Introduced. — The quantity of heat, Q, to
be supplied to keep the temperature of
the expanding air constant is found from
eq.(26), to be,
Q^ap.log.jjf.
The expansion being supposed to follow
Boyle's law, we have,
* Po
Pfi=PJ>«
Hence we have,
or
Pi
2. The Injection of Hot Water into
the Cylinder of the Compressed- Air
Q=^nap,log.|j:j. •
1^ = 1 in this case since the air is expand-
I ed down to atmospheric pressure. From
I this formula the weight of water to be
I injected is calculated as in table. The
results are given in the following:
Table IX.
Absolute press-
Quantity of heat to
Weight of water to be injected into the work-
be supplied to keep
ing cylinder per kilogramme of compressed
the compressed
air is intro-
duced into
the working
cylinder.
the temperature of
air introduced to keep the final temperature
the air from falling
from falling below 0° C.
below 0° C. during
its expansion down
to atmospheric
The temperature of the water introduced being
pressure.
20° C.
50° C.
100° C.
2
13.280
.134
.103
.074
3
21.030
.212
.163
.117
4
26.550
.262
.206
.148
5
30.828
.311
.240
.178
6
34.334
.346
.266
.192
7
37.285
.376
.289
.208
8
39.833
.402
.309
.223
9
42.094
.425
,326
.235
10
44.106
.445
.342
.247
11
45.945
.464
.356
.256
12
47.612
.480
.369
.266
13
49.145
.496
.381
.274
14
50.562
.510
.392
.282
15
51.885
.524
.402
.290
The quantities of water here given are
the minima values since the latent heat
which is released by the water in freezing
has not been taken into account. Hence
494
VAN NOSTRAND'S ENGINEERING MAGAZINE.
to avoid the formation of ice we must
add a slight excess of hot water.
3. The Effect of the Conduction of
Heat by the Cylinders, Pipes, &c. — Since
the temperature of the compressed
air when used is most always that
of the surrounding atmosphere, the
result of the conduction of heat by the
containing vessels is the dissipation of
the total heat of compression. The me-
chanical equivalent of this heat is, of
course, lost work, and, as it is most
economical to get rid of this heat during
compression, conduction and radiation
from the compressor is an advantage.
Since, in working expansively, there is a
tendency for the cylinder to become
colder than surrounding bodies, the con-
duction and radiation of heat is here too,
if anything, an advantage.
In all our formulas and results hitherto
established, the cylinders have been sup-
posed non-conducting; and the investi-
gations of M. Mallard have shown that
this hypothesis is justified. For the heat
leaving the compressor by conduction
and radiation is in part compensated for
by that developed by the friction of the
piston; and the heat conducted through
the working cylinder is very small rela-
tively to that converted into work.
Hence, any passage of heat by conduc-
tion of the cylinders belongs to those
secondary quantities which are always
omitted in the general theory of motors,
except so far as allowed for by proper
coefficients.
CHAPTER VIII.
American and European Air-Com-
pressors.
I.
PUMP COMPRESSORS.
Pump or plunger compressors are
generally in high repute in Germany and
Austria, especially in mines, and they
seem to give very satisfactory results.
In the United States they never have
been used to any considerable extent and
are now not at all used.
It must be said to the prejudice of
these compressors, that, in consequence
of the large mass of water to be pushed
back and forth by the plunger, a large
per-cent. of power is wasted in over-
coming inertia; that high piston speeds
are, in consequence of the violent shocks
which result, utterly impossible; that
they are very heavy and hence require
expensive foundations; that when the
prime mover is run at a high speed, a
more or less cumbrous, expensive, and
wasteful machinery of transmission is
necessary; that their use is limited, press-
ures of 5 or 6 atmospheres being their
utmost capability, on account of the
large quantity of cooling water taken up
by the air at even moderately high ten-
sions; that a large amount of cooling-
water is required to produce a compara-
tively small effect in the abstraction of
heat.
On the other hand, it must be ad-
mitted that these compressors are liable
to very few repairs, that they are simple
in construction and that " dead spaces "
are avoided.
The hydraulic or ram compressors
first used by Lommeiller at the Mt.
Cenis Tunnel have become obsolete.
II.
SINGLE-ACTING WET COMPRESSORS.
The air compressors now used in the
United States are either "Dry Compress-
ors " in which the cooling is effected by
flooding the external of the cylinder, and
sometimes also the piston-rod aid-head,
with water; " Wet Compressors" by the
injection of water into the cylinder-space,
as well as by external flooding; compress-
ors with no cooling arrangement are
seldom used, and only in temporary and
cheap plants.
Compressors with a partial injection
of water have been used to very good
effect in the United States. Most of
these are single-acting, and are repre-
sented by the machines of Burleigh, of
Fitchburgh, Mass. The cooling is very
efficient and hence the useful effect is
considerably increased. They are very
durable and not liable to get out of re-
pair, as is shown by the record of Bur-
leigh's machines which have stood the
test of years of steady work.
The use of single-acting compressors
renders it necessary that, in all cases
where anything like a uniform supply of
air is needed, to have two compressor-
cylinders. These cannot be driven
directly from the piston-rod of the
driving engine, but necessitate an in-
directly coupled-connection of some sort.
TRANSMISSION OF POWER BY COMPRESSED AIR.
49&
All this makes single-acting compressors
somewhat cumbrous and expensive.
As built to-day, the evils of dead
spaces, and of jars and shocks resulting
from water in the cylinder, have not been
duly considered. There are also a few
cases when the sectional area of the
inlet-valves is insufficient; and in gener-
al those parts which are most liable to get
out of repair are most difficult of access.
We are inclined to think that the
claim of the Burleigh Co., that their
compressor is the most efficient, economi-
cal, and durable of any built in this
country, cannot be far from the truth.
III.
of the steam used. The amount of free
air compressed at a piston speed of 350
feet is about 1000 cubic feet per minute.
A greater pressure of air than the press-
ure of steam used is obtained by increas-
ing the size of the steam cylinder, or
decreasing that of the air cylinder.
The best double and direct acting
compressor of the wet kind is undoubt-
| edly that of Dubois Francois, built in
i Seraing, Belgium, and exhibited at the
j Centennial Exposition, in 1876.
Dry compressors, although the cheap-
\ est as regards first cost, are not the most
; economical in working. But where air
i is to be carried through pipes exposed to
great cold they are the only alternative,
DOUBLE AND DIRECT-ACTING COMPRESSORS.
Up to within several years ago, single- j
acting compressors have been used |
almost exclusively. Now the double j
and direct-acting compressor seems to \
be superseding it. This is now the
leading type of American compressor, |
although hitherto it has given at least no j
better results than the best single-acting j
machine.
Superiority in the double-acting com- j
pressor is found in its simplicity. The I
piston of the engine drives the compress- !
or by a direct connection. All wasteful !
and cunibrous machinery of transmission |
is at once unnecessary and high piston-
speeds are possible; in the United States j
from five to seven feet.
Most American double and direct-act- j
ing compressors are of the dry kind, i
These have the advantage that the air is j
delivered without having any water |
mechanically mixed with it. Hence j
very much ice cannot be formed when
the air is worked expansively. Higher j
rates of expansion are possible than with I
air from a wet compressor.
One of the very best American double j
and direct-acting dry compressors is the j
" National," built by Allison & Brannan, \
Port Carbon, Pa., (Office, 95 Liberty St., i
N. Y.). Steam cylinders of the medium j
sized duplex machine are 12"x42", and j
the air cylinders 15"x42". The air j
pistons work to within one sixteenth of j
an inch of the cylinder heads. The |
water circulation for cooling passes j
spirally around the air cylinder from the
center to each end. The engine will
compress air to the same pressure as that
IV.
DESIGN AND CONSTRUCTION.
The efforts of builders and engineers
should be directed to the attaining of a
higher efficiency, and they should not, as
is now often the case, sacrifice the latter
to cheapness and small dimensions. To
attain such desirable efficiency the heat
of compression must be more effectually
abstracted. This must be done by a,
more ingenious and rapid circulation of
water around the cylinder, and injec-
tion of water in the form of spray into
the cylinder. But the injection of water
in some efficient and practical manner,
which is so essential to the reaching the
highest efficiency, introduces the great
disadvantage of having to work with
wet air. Hence we see how important
would be an invention of means or ap-
paratus for separating the water from
the air when direct intercontact has
been had to keep down the temperature.
We must also remember the important
physical fact that water absorbs very
considerable volumes of air — volumes
dependent upon the pressure of the air
and the amount of surface of water ex-
posed to the fluid contact, time being
also an important factor.
Clearance must be reduced to the
smallest possible amount. It has been
brought down in a few cases to 0.39
inch. A long stroke, one from 2 to
to 3 times the diameter of the cylinder,
is another means of avoiding loss from
dead spaces, since here the air which
fills the dead space is small in compari-
son with that actually delivered. The
496
VAN NOSTRAND'S ENGINEERING MAGAZINE.
valves must be so placed that, between
their seats and the piston-head at the
end of the stroke there shall be the
smallest possible clearance.
The valves themselves, to close the
more rapidly, are made to have only a
very small travel. (This has been made
as small as .08 to .12 inch.) The
valve-area must be made large enough
by increasing the number of the valves.
The valve-area should be amply large,
generally from \ to -^ of the sectional
area of the cylinder. The valves should
be so attached to the cylinder head that
they may be removed and repaired with-
out taking off the latter or otherwise
taking the machine apart.
Great care must be taken to have the
piston head fit the cylinder accurately
and closely, since, especially in dry com-
pressors, great losses result from any
looseness. The piston-heads should be
made so that they can be adjusted to
preserve a nice fit, as in steam engine
practice. Lubrication of the cylinder in
case of the dry compressor should be
effected by automatic oil cups placed
upon it.
It must also be borne in mind that the
working pressure is that which most
influences the physical conditions of
working, and the suitable mode of con-
struction. And, although the loss of
work increases with the pressure, yet the
rate of variation of the loss of work
decreases as the pressure increases. As
great a proportion of work is lost by
increasing the pressure from two to three
atmospheres as by increasing it from
five to ten atmospheres.
The tendency in Germany and France,
as well as here, is for the wet compressor
entirely to supersede all others. But it
is scarcely too much to say that the
air- compressor of the future has yet to
be invented.
CHAPTER IX.
Examples from Practice.
I.
The Eepublic Iron Company of Mar-
quette, Mich., have done away with the
use of steam, by utilizing the power of a
water-fall situated about a mile from
their works. The power is transmitted
by means of compressed air which drives
all their machinery, ^and thus saves the
cost of fuel.
There are four compressors, 24* diam-
eter and 5' stroke, driven by two turbine
Swain water-wheels 5 J' diameter, under
16 feet head of water. As near as has
been ascertained, they have about 450
horse power at the wheels. The air is
carried one mile in a pipe built of boiler
iron, 15" inside diameter. About 66 per
cent, of the effective power of the wheels
is obtained at the mines and shops.
II.
ECONOMY PROMOTED BY THE USE OP
COMPRESSED AIR.
To show the great saving of both time
and money since the introduction of
compressed-air machinery we will give a
few figures.
It cost the Golden Star Mining Co., of
Sacramento $12 to $15 per foot to run a
tunnel 1X^7 feet when employing hand
labor; after introducing air machinery
it cost them $6 to $7 per foot; with
hand labor they made a distance of two
feet per day; with machine labor, a dis-
tance of six feet per day.
.Another instance, among many, is
that of the Sutro Tunnel Company of
Nevada;
Expense by hand labor per
month $34,000 to $50,000.
Expense by machine labor
per month $14,000 to $16,000
III.
COMPRESSED-AIR MOTOR STREET CAR.
The pneumatic engine which has been
on trial by the Second Avenue Railroad
Company, on the Harlem portion of their
road, from the Station at Ninety-Sixth
Street, to Harlem River, at One-Hundred-
and-Thirtieth Street, has proved so satis-
factory to the company that it has au-
thorized the construction of five more
engines.
These are to be used exclusively on
the upper part of the road, where it is
proposed to dispense entirely with the
use of horse power, so soon as the
requisite number of engines shall be pro-
cured. It was stated at the company's
office yesterday that the most sanguine
expectations had been fulfilled; the new
engine could be run at a trifling cost,
and without the noise and smoke and
TRANSMISSION OF POWER BY COMPRESSED AIR.
497
smell of oil which accompany the use of
steam; any rate of speed which was
likely to be required could be maintain-
ed, and the engine was under as complete
control of the engineer as one propelled
by steam or a car drawn by horses. It
was not known whether any change was
proposed below the station at Ninety-
Sixth Street; certainly none at present.
The new engines are manufactured by
the Pneumatic Tramway Engine Com-
pany, whose office is at No. 317 Broad-
way. Some time ago two Scotch engi-
neers, Robert Hardie and J. James, in-
vented a system of propelling cars by
means of compressed air. The invention
was examined by a number of practical
railroad men who were visiting Scotland.
Hardie and James were induced to visit
this country and the company was or-
ganized. Experiments have been making
for a year, resulting in improvements
which now seem likely to render the in-
vention serviceable to the public. The
motive power is condensed air, contained
in two reservoirs, placed one under each
end of a car, which is similar in con-
struction to those in ordinary use on
street railways. The air is pumped in by
a stationary engine at one hundred an<#
twenty-seventh street, and this has been
so far improved that the reservoirs in
the cars now used are filled in a few
minutes. These are of steel, and are
tested up to a strength many times
greater than their working pressure, and
it is claimed that there is no danger of
explosion. The machinery is simple and
not liable to get out of order. The air-
tanks of the experimental car are only
sufficiently large to enable it to make
one round trip between Harlem and
Ninety-Sixth Street stations ; but the
cars now building will be larger and will
contain reservoirs of much greater
capacity ; and it is claimed that there
will be no difficulty in constructing them
so that the round trip from Harlem
river to Peck Slip can be made without
replenishing.
Mr. Henry Bushnell, of New Haven, is
the inventor and constructor of a new
compressed air motor street car, the
chief peculiarity of which is that he is
able to force air into his receivers until
his gauge registers the enormous pressure
of more than 3,000 pounds per square
inch. His receivers are tubes, the largest
Vol. XIX.— No. 6—32
of which are twenty feet long, and only
eight inches in diameter, inside measure-
ment. There are four of these, two
lying side by side above the axles, and
next to the wheels on either side of the
car. Between them at one end are four
other tubes, each six feet long and six
inches in diameter, inside measurement.
The material is wrought iron three-
eighths of an inch thick, and are welded
in. The double cylinder engine which
utilizes this air in turning the wheels of
the car does not differ materially from a
steam engine, except that its two cylin-
ders are only two and three-fourths
inches in diameter, inside measurement.
The machine built by Mr. Bushnell to
compress the air consists of three steam
air pumps. The first and largest is
merely a feeder to the second. The air
that comes from it is condensed to a
pressure of about six pounds. This den-
ser air is more worthy the prowess of
the second pump, which in turn crushes
it into a greatly smaller compass. The
third pump gives the final pressure.
The gauge on the compressing machine
has registered 3,500 pounds per square
inch. The plungers of the second and
third pumps have no heads. They are
merely rods of steel forced into vessels
containing oil. As the plungers move
out and in, the surface of the oil falls
and rises, admitting the air through one
valve and forcing it out of another. It
is, therefore, necessary to have the pack-
ing of the plungers only oil tight, not air
tight, under the tremendous pressure.
Air, like all other substances, gives out
heat while being compressed, and it is
necessary to cool the chamber that first
receives the air from the third pump by
a covering of cotton waste saturated
with water. On the other hand, the ex-
pansion of the air as it is given off at
each half revolution of the car engines
absorbs heat, and after running the car
for a short time the engine cylinders and
escape pipes are whitened with frost.
This coolness destroys in part the elas-
ticity of the air as it enters the cylinders.
To remedy this Mr. Bushnell will sur-
round the cylinders with stout metal
jackets, beneath which he will force air
with the aid of a small pump geared to
the machinery of the car. This newly-
compressed air, he says, will supply heat
enough to keep the cylinders warm.
498
van nostraistd's engineering magazine.
The writer rode recently on the new
car as far on the Whitneyville road as
Mr. Bushnell could go without interfer-
ing with the trips of the horse cars. The
motion was easy, and at times about
twice as rapid as that of a horse car.
The new vehicle obeyed the engineer
promptly in starting and stopping. The
distance traveled in going and returning
was a little over a mile. At the start
the guage registered 1,800 pounds. At
the return the pressure indicated was
1,500 pounds. When the air was 'al-
lowed to escape from a turned cock the
roar was frightful and was as irritating
to the ear as escaping steam. In run-
ning, however, very little noise is heard
from the escape-pipe, because the es-
caping air is made to pass through a
mass of ordinary curled hair. This device
Mr. Bushnell esteems one of the most
important of his inventions. He has no
doubt that it would prove equally effica-
cious in deadening the sound of escaping
steam.
Friends of Mr. Bushnell claim that he
could never make a receiver capable of
retaining air at the high pressure he had
in view. The air that was in the tubes
last Thursday was pumped in, he says,
on the 25th of June. The gauge then
showed 2,100 pounds. The pressure
gradually lessened until two weeks ago,
when it was 1,900. After that time a
small leak was discovered. This leak
was closed with a turn of the wrench,
and after that not a pound was lost up
to the trial, when 100 pounds was
allowed to blow off to gratify the curi-
osity of visitors just previous to the
short trip referred to.
Mr. Bushnell called attention to the
small diameters of his largest tubes.
He said that a pressure of 2,000 pounds
per square inch would give, by calcula-
tion on the head of each tube, an aggre-
gate pressure of fifty tons; while the
two-feet heads used by the inventor of a
rival compressed air motor would have
to withstand an aggregate pressure of
180 tons, if a pressure of 800 pounds per
square inch should be put on, as the in-
ventor claimed was possible. The heads
were necessarily the weakest parts of the
tubes. A welded joint, such as his were,
was usually reckoned twice as strong as
a riveted one.
On a previous occasion Mr. Bushnell
made a round trip on his car on the
Whitneyville road, a distance of a little
over four miles. The pressure was then
reduced from 1,950 pounds at the start
£i 750 pounds on the return. A com-
pany called the United States Motor
Power Company has been formed, and
Mr. Bushnell is its president.
ARCHITECTURAL CEMENTS.
From "The Engineer."
Portland cement has unquestionably
proved a most important gift to the
architect and builder. Viewed sestheti-
cally it was an immense advance upon
the ugly red-brown "Roman" cement of
Parker; still, as an ornamental material
for plastering external surfaces, and
casting into decorative forms it has some
grave defects. Chief of these to the
artistic mind is its cold ashy grey color,
and the minutely porous texture of its
finished surface, which is rapidly render-
ed darker and more gloomy-looking by
the deposit in its innumerable porosities
of minute particles of London smoke
and soot. Portland cement makers have
speculated in a desultory manner upon
the great improvement which would be
effected, if materials could be found not
requiring more expensive manipulation
than those necessary to produce the
existing cement, but which should yield
a product having a more sunny tint
than the cold leaden color of Portland
cement, one, in fact, more nearly resemb-
ling the actual shade of a clean building
of the best Portland or Bath stone.
There are some considerable difficulties
in the way of introducing such an im-
provement, for so intense are the color-
ing powers of the peroxides of iron and
manganese in combination with the
earthy bases and with silica, that a mere
trace of either or both of these oxides is
ARCHITECTURAL CEMENTS.
499
sufficient to remove all whiteness or
purity of tint from cements produced
from the materials ordinarily employed.
The glass manufacturer, and to a con-
siderable, though less extent, the brick-
maker, can largely remove or greatly
modify in the processes of fusion or of
kiln-burning the tints of their manufact-
ured articles; but the processes employ-
ed by the glassmaker are too delicate
and expensive to be applied to the
decoloration of the materials of cement,
and the direction for improvement must
rather be looked for in the scientific
choice of the materials themselves than
in any chromatic changes to be wrought
in them during the processes of manu-
facture. In France some progress has
been made in this direction. In the
south a manufactory which still bears
the historical name of Vicat, situated
not far from Grenoble, produces, from
combinations with the limestones of
Dauphiny, a plastering material which
has really the sunny color of those
softer varieties of Bath stone which
were so largely applied by Sir William
Chambers and his successor, Gandon, to
internal decorative carving, fine examples
of which may be seen in the interior of
Chambers' noble structure, the Custom-
house of Dublin. It is stated on good
authority that amongst the multitudin-
ous beds of calcareous stone which crop
out along the coast around Boulogne,
one or more thin beds of a very light
yellowish color are found which produce
a cement of the desired bright tint.
There are immense Portland cement
works at Boulogne, but the demand is
chiefly for constructive purposes upon a
great scale, and little attention seems to
be there given to the fineness of tint of
the cement, and a very small rival manu-
facturer, who, we believe, was the
discoverer of these fine tinted beds, was
stopped by his colossal rivals, who pur-
chased the deposits from under his feet.
It may be noticed also, that in Ireland —
where, as yet, we believe, all the Port-
land cement employed is imported, none
being manufactured — there is an im-
mense assortment from which to select
suitable argillaceous limestones. These
are to be found in various localities —
more especially in the tilted up beds
which are found cropping out at highly
inclined angles for several miles to the
westward of Drogheda, along the north-
ern bank of the river Boyne. Scarcely
two of these beds are quite alike in
composition. There are thick beds of
almost pure crystallized carboniferous
limestone, and there are hundreds of
various composition, none being very
massive, running into limestones so
clayey and siliceous that they will not
burn into lime at all in the ordinary kiln.
During the presidency of the late Sir
John Burgoyne, as chairman of the
Board of Public Works of Ireland, at a
time when hydraulic lime equal in
quality to that of Aberthaw was largely
needed for the works of improvement
then going On upon the river Shannon, a
member of the Board, Mr. Radcliffe,
conducted for his own information an
extensive but desultory series of experi-
ments upon the diverse calcareous
minerals of Ireland that might produce
hydraulic contents, and amongst these
many of the beds along the Boyne were
subjected to experiment, and some pro-
duced hydraulic cements of considerable
hardness, and of great beauty of color.
Mr. Radcliffe, however, was no chemist,
and had much of the red tape of his
office to attend to, and often obtained
through his scientific ignorance anoma-
lous results which he could neither trace
nor explain, and which at length dis-
gusted him, and the further prosecution
of the research was abandoned. A large
body of data of more or less value was,
however, collected, chiefly through the
intelligent assistance of Mr. Charles
Scanlin. The results obtained may,
perhaps, still exist in the archives of the
Board at Dublin. The circumstances
have so far been here alluded to, how-
ever, because the immense repertory of
calcareous and silico-aluminous beds
remain, we believe, still to reward with
success the energy and skill of whoever
shall bring them into use. Their posi-
tion, as above indicated, is favorable for
the establishment of a cement manufac-
tory, the materials being abundant.
Coal, though imported, is nearly as
cheap as anywhere else in Ireland, and
the means of distributing the manufac-
tured article are ready. A richly color-
ed cement, having the other properties
of Portland, would soon command a
large sale and introduce a new manu-
facture almost wholly from native
500
VAN ^STRAND'S ENGINEERING MAGAZINE.
materials, to Ireland, which at present
can boast of little else in the way of
manufactures, except those of porter
and whiskey.
Another cement is conceivable, of a
decorative character and nearly color-
less or pure white when in mass, which
would seem eminently worthy of atten-
tion, to produce which, however, we
must look in another direction than to
the sedimentary rocks. Calcareous min-
erals, as chalk, and the white marble of
Donegal, are easily obtained. The
difficulty begins when we look for a
material containing soluble silica in
abundance, and freed from the discolor-
ing elements of iron and manganese.
Now; amongst the secondary products
of volcanic districts, we have a source,
as good as it is inexhaustible, of what we
need. Almost all lavas, but especially
the colorless, or but slightly colored
trachytes, when exposed to the vapors
which are exhaled from the fissures
called fumaroles, are well known to all
who have visited the popular wonder of
the solfatera near Pozzuoli. The vapors,
emitted in all similar fissures in volcanic
districts, of hot steam mingled with the
vapor of hydrocholoric acid, and of sul-
phurous acid, slowly passing by higher
oxidation into sulphuric acid, act with
surprising energy in reducing the hard
crystalline trachytes into a soft, plastic,
and often colorless mud, and by further
decompositions frequently into hyalite,
which in the lapse of time becomes con-
verted into various varieties of opal, as
found now in the great tufa beds of the
extinct volcanic regions of Hungary.
These decompositions and their results
are seen in a vast scale in the siliceous
linings of the Geyser basins in Iceland,
in New Zealand, and in that wonderful
natural volcanic museum, the national or
people's park of the future, in California.
In any quantity these natural compounds
of more or less soluble silica, and as
colorless as ice, may be had for the
trouble of collection and transport.
With pure limestone, and with these
remarkably pure hydrated silicas, in
composition with more or less of equally
pure alumina, it would seem quite prac-
tical to procure a cement for internal and
perhaps external decoration of dazzling
whiteness and beauty, and which from
its closeness of texture would not be-
come discolored by the coal smoke of
our cities, and which would bear wash-
ing whenever necessary. The eyes be-
come so habituated to the roughish and
grenu surfaces of Portland and other
building stones as well as of cement,
that fancy suggests that a fine smooth
close-grained surface for the exterior of
our buildings is unsatisfying to the eye.
Any one, however, who will examine the
fagade of a large building — a bank, we
believe — in Cockspur-street or Trafal-
gar-square— we know not which it
should be called now — nearly facing and
to the south-west of the Nelson column,
which has been constructed of Sicilian
white marble, may easily see that a
smooth, hard, white external surface is
quite consistent with architectural beau-
ty, and possesses immense advantages in
the smoky atmosphere of London.
For internal decorative purposes it
would be needless to enlarge upon the
value of a material that would possess
far greater beauty in color and texture
than plaster of Paris; would be non-ab-
sorptive, little attractive of smoke, not
easily scratched, and which might be
washed again and again. Every one
who has examined the interior of the
decorated rooms of Roman villas at
Pompeii will have been struck by the
smoothness, density, and hardness of the
colored surfaces of stucco, upon which
the plain color and fresco paintings of
the walls have been laid. The common
belief is that this stucco has been mainly
formed of lime mortar, more or less
mixed with- gesso or plaster of Paris.
We are, however, by no means con-
vinced that the true composition of the
material has been revealed by the im-
perfect analyses and earless examinations
of modern times. It is somewhat diffi-
cult to obtain specimens for examination,
for every morsel, however fragmentary
and valueless, of this or of any other
material to be found in the rubbish
heaps of Pompeii is rigidly prevented by
the guardians from being removed by
the visitor who can only secure a speci-
men by the troublesome and round
about process of obtaining an official
order from Naples. The observer is,
however, struck by the remarkable fact
that polished fragments of various diff-
erent and brilliant colors abound in the
rubbish heaps of Pompeii which, after
ARCHITECTURAL CEMENTS.
501
eighteen hundred years' exposure to air
and moisture, and to the corrosive vapors
which everywhere permeate the porous
soil about Vesuvius, are as hard, smooth,
and brilliant as when they left the hand
of the workman. A more careful exam-
ination than has yet been made of these
stuccos might yet reveal the process of
their formation, and perhaps show that
the soluble silicates produced by second-
ary volcanic reactions, such as we have
spoken of, were employed in their
formation.
The economic uses to which several
volcanic, products may be applied open a
vast and, as yet, almost untrodden path
of useful discovery. One of the valuable
uses to which these may be employed is
largely known to the house decorators of
Rome and Naples. Certain trachytes
when fully decomposed by fumarole va-
pors, finally fall into an impalpably fine
and soft powder without coherence, of
various beautiful delicate pearly-white
tints, which are used as the coloring
material for ceilings and plastered walls
in place of whiting when applied with
size. The character of delicate and
slight broken color thus given is greatly
superior to the eye of taste, to the cold
dull white of our whitened ceilings and
walls. It is also in texture much more
satisfactory to the eye. The lime beds
of Vufa which abound around Vesuvius
and in Auvergne, are to be found of
every color and tint, from pure white,
such as is the "domite" of the Puy de
Dome, to buff, yellow, red, and brown,
into almost coal black; indeed all these
tints occur together in super-position in
the masses of tufa, generally of impal-
pable fineness, over which one ascends to
the crater of the volcano in the Lipari
Island of that group. A miserable,
abortive attempt has for many years
continued a struggling existence to ex-
tract such chemical substances as boracic
acid, sulphur and alum, from the ejecta
of volcanoes, but neither these, nor, so
far as our knowledge extends, in any
other volcanic district in Europe, has
any well-considered attempt been made
to utilize for architectural or other eco-
nomic purposes the vast deposits of
colored and pulverulent tufas — unless,
indeed, we except the use made for the
production of an hydraulic cement from
certain tufas which are dug out by
excavating into certain parts of the huge
cone of Sarconi, in Auvergne. There
can be little doubt that many volcanic
tufas would consolidate by mere mechan-
ical pressure, and a little baking into
tessarse, of various sizes that might be
employed for laying ornamental mosaic
flooring of much greater beauty and far
cheaper than our English encaustic til-
ing, which by the large size of each tile,
in proportion to the apartment which
they floor, and the harsh and gaudy
coloring but too generally offend a culti-
vated eye. Whether these or any other
tufas would per se by pressure alone
become sufficiently hard and coherent or
not, it does not admit of doubt that by
suitable admixture with calcareous or
siliceous matter, or both, they would
become so. The manufacture would be
well suited to Italy and Central France.
In Great Britain we are fortunately
exempt even from dying-out volcanic
action, although we have in the products
of remote geological epochs, especially
in the North of Ireland, abundant beds
of lavas and trachytes which would
readily suffer decomposition into soluble
silicates if exposed to sol fatara va-
pors.
May we not artificially produce and
! utilize these vapors ? Hot steam we can
I have at the expense of some coal. The
j alkali makers of Widnes, Glasgow and
I Belfast, as an educt of the process of
j decomposing common salt by Le Blanc's
j process for the purpose of making " salt
! cake," as it is called, and ultimately
; crystals of carbonate of soda, evolve
j millions of tons of hydrochloric acid va-
| por which used to fly into the atmos-
phere— until that nuisance was remedied
by legal enactment — and the acid vapor
compulsorily condensed to run into the
sewers to waste. Sulphuric acid or vit-
riol is at hand in all these vast works as
a necessary element for the decomposi-
tion of the chloride of sodium. We
have here, therefore, on cheap terms, all
the conditions requisite for the produc-
tion of an artificial solfatara where we
please, so that by the help of a little hot
steam, hydrochloric acid, and sulphurous
acid vapors commingled, we may at an
extremely small cost decompose and
convert into useful products such trachy-
tes as may be found nearest and most
suitable.
502
VAN JSTOSTRAND7 S ENGINEERING MAGAZINE.
THE ORIGIN OF METALLURGY— THE BRONZE AGE,
From the French of EMILE BURNOUF, by CHRISTOPHER FALLON, A. M.
Translated for Van Nostrand's Magazine.
I.
We are ignorant as to the date of the
first appearance of mankind; we have
no foundation upon which Jto rest the
chronology of the primitive times. His-
tory dates only from yesterday, and yet,
among the different nations, presents but
fabulous origins. There is no more real-
ity in the first facts related by Titus
Livy than in the genealogies of the
Grecian heroes. Adam and Eve are an
agreeable myth, borrowed perhaps from
Persia in the times of captivity; their
descendents are the personification of
families or of tribes. Grecian chronol-
ogy goes back about six thousand years
prior to our era, but is likewise preceded
by a long mythological period. The
same may be said of India and China.
After all, what are six thousand years ?
Already have a .hundred passed since
the French revolution, and does it ap-
pear long to any one ? Now-a-days
events follow each other very fast and
progress is rapid, because we possess
forces, both physical and moral, of enor-
mous power, by means of which we
transform the earth and ourselves.
When our ancestors possessed them not
their advances were slow, their achieve-
ments small and casual. How can the
ocean be traversed, or a large sheet of
water crossed without boats, and how can
we construct boats if there are no tools of
iron or some substance sufficiently hard
to work wood, to adapt the pieces and
render them imperveable to water ? Let
us consider the objects we make use of
to-day to clothe, shelter, nourish and
convey ourselves from place to place, to
procure light, heat, books and so many
products of science and art which adorn
our households. It will readily be seen
that there is not one which does not
suppose the possession and successful
employment of the metals. We are
now all aware that men have not known
them at all times. For a great number
of years, they did not possess any, ex-
cept perhaps a few grains of gold which
nature spontaneously gave them, and
which they collected here and there on
the banks and in the channels of rivers.
It was this period which has been called
The Stone Age, and the tools those
unfortunate men have left behind them,
as evidence of their industry and necessi-
ties, are all made of hard stone, of silex,
of diorite, of absidian and of trachyte.
This long period of the infancy of man
is attested by the strata in which these
objects are found, buried beneath
mounds of earth which have required
centuries for their formation; but the
actual geological period had not yet
begun when man was already in exist-
ence living among mammoths, bears in
caves, and other animals now no longer
to be found. In the first place it was
necessary that a man having selected a
stone on which to put an edge, should
strike it with another in order to scale it.
Thus were the first hammer and the first
hatchet made; and all other instruments
being made in like manner, have given
the name of The Period of Unpolished
Stone to the era during which this rudi-
mentary industry lasted. Little by little
it was found that certain stones could by
means of continued rubbing wear others,
which were even harder, and so friction
was substituted for percussion in the
manufacture of tools. In this way sharp
hatchets and scissors were made; round
hard stones were bored and handles
inserted. Smaller stones of finer quality
or brighter color were shaped and
pierced and then used as beads. Arms
were made in the same way. It was
this second period of humanity which
has received the name of The Period of
Polished or Neolithic Stone.
From the beginning, or at least from
an early date, men attempted to mould
clay into uses of different kinds. This
work was done by hand during the
entire age of stone. The potter kneaded
the clay with his fingers, the impression
of which is yet seen on the pottery of
those early times. It required constant
observation and new means of action to
enable the potter first to discover the
value of the movement of a wheel, and
then to construct one. In fact the turn-
THE ORIGIN OF METALLURGY.
503
ing lathe seems to have been unknown
during the whole period of which we
speak, but the baking of vases dates far
back, for from the time that men could
light fires, they observed on their hearths
pieces of argil become insoluble by the
heat. The black, red or yellow clay
which nature furnished them in many
places, enabled them to color or paint
these roughly made vases; they then
polished the surface yet soft, by means
of a stone burnisher and engraved fan-
tastic figures thereon.
Then came the first metal, which let
us say was the common metal, copper.
The knowledge of gold certainly preced-
ed that of brass, because gold is found
in its natural state in many countries. It
no doubt was the same with silver, the
extractions of which is not very difficult;
perhaps the same should be said of lead,
for from the time globules of metal were
found in the ashes of the fire, the man
who noticed them, must have wanted to
know the ore from which it was extract
ed, and having found it, must have
sought for more in the mountains.
Substances which are producible in
hearths, by the mere burning of minerals,
must have been first discovered, as lead
and glass; artificial glass, usually blue,
is found among the objects of personal
ornament of the most ancient times.
On the other hand, when the extraction
of a metal requires a high temperature,
or a chemical operatiou, it may be con-
ceded that such a metal was discovered
long after the others and after a number
of ineffectual attempts. Copper is found
native,butin very smallquantities; copper
pyrites resembles gold, still the metal is
obtained only by complicated operations,
as is the case also with tin. Finally
after obtaining these two substances, it
is necessary, in order to form bronze, to
make a fusion — which is attended with
difficulties. The bare idea of uniting
two metals does not readily present itself
to the mind, and when once conceived it'
is yet essential to learn in what propor-
tions they must be used in order to form
a new metal, more useful than either.
Bronze appeared in the West when
the art of polishing stone had arrived to
a state of perfection. We have in our
museums instruments of hard stone
made anterior to the appearance of
bronze, which our own workmen would
not make better nor in any other manner;
only they would probably make them
faster, for they have means of action
and processes which the ancients did not
possess. Bronze, at first scarce, became
more common in the course of time.
Those fabricating it could dispose of it
in other countries only in exchange for
other objects of the same value but of a
different kind. These objects of ex-
change caused a demand which could be
supplied only by discovery, or by obtain-
ing them elsewhere in sufficiently large
quantities to give rise to commerce. The
discoveries of which we are about to
speak have proved that the quantity of
bronze kept increasing, that with this
new metal many instruments were man-
ufactured which were previously made
of stone, that new ones were invented,
and that a time arrived when the substi-
tution of bronze for stone was, so to
speak, complete.
The Bronze Age was for a short time
co-existent with the period of polished
stone. There is then a period of transi-
tion when these two substances were, in
a measure, blended together, and might
be comprised under the same title in the
age of stone or in that of bronze. It
would be a mistake, however, to suppose
that metal caused the hard stone to dis-
appear entirely when the superior quali-
ties of the former were discovered, as
stone continues to be used for many
pin poses in many countries where neither
bronze nor even iron has as yet supplant-
ed it. Thus those hmall double-edged
blades made of obsidian or si lex, known
as knives, still in use in the Grecian pen-
insula, in Asia minor, in Palestine, and
no doubt in many other countries, are
fastened to pieces of wood and used by
the peasants to thrash their wheat or cut
their straw. They are of the same
shapes as in the bronze age and are made
in the same way; but the predominance
of metal over stone, and the abandon-
ment of the latter, in most cases in which
it was employed, characterize the long
era which followed that of transition
and which constitutes the bronze age
properly so-called. In the same way
that this metal was substituted for stone,
it happened that a new metal concurred
with bronze, and was used instead wher-
ever there was a decided advantage in
so doing.
504
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Discoveries which were made only
twenty years ago, and which since then
have been repeated throughout Europe,
have enabled us to fix the period of
transition from bronze to iron. It dif-
fers from that which has been called the
first age of iron, and which has, for a
long time, been well ascertained. During
the latter, iron already takes the first
rank and awaits only to be brought to a
state of perfection. The transitory
period is marked by a slow and progres-
sive substitution of the new for the old
metal, and by a reciprocal influence from
one to the other. When iron first ap-
peared in Europe, it met the same fate
which bronze a few centuries previously
had experienced. It was a rare and
precious substance and lost its value
only by its increasing abundance, and
when it could be converted into tools,
utensils and arms, which were formerly
made only of bronze. The oldest ob-
jects of iron found are bijoux and orna-
ments, for even in those early times
there were rich and poor men, and those
alone could obtain articles of iron who
had other valuable objects to exchange.
Do we not see the same thing in our own
day ? We assisted, a few years ago, if
not in the discovery at least in the
economical extraction of aluminum.
This metal until then confined to labora-
tories, became an industrial product, but
as the preparation is yet expensive it is
worth twice as much as silver, and is
employed in making ornaments and
fancy articles. Yet it is not less com-
mon than iron in nature; it is the base
of all clays and possesses qualities which
can — which ought to make it preferable
in certain cases to silver, to brass or even
to iron. It needs but new processes of
extraction to render it as abundant as
the latter.
Iron has not entirely supplanted bronze,
as the latter is still much used, nor would
aluminum and all the other metals cause
iron to be abandoned : but a new sub-
stance may answer many purposes better
than those that have preceded it, and
for this reason be preferred. For a long
time hatchets were made of stone, but
were set aside when they could be made
of bronze; bronze hatchets were the
only ones to be found for many centuries,
but were also abandoned when iron ones
became sufficiently abundant to com-
pete with them in the market. The
period of transition from bronze to iron
is well characterized in many ways, of
which we shall speak hereafter. There
is no doubt, at present, of the reality of
this change, and it is even becoming ap-
parent how this transition was accom-
plished, the course the metals have taken
to spread from one mart to another,
until they have reached the most remote
countries of Northern Europe; but be-
fore exhibiting these grand discoveries
of our day, I must give an account of
the progress which science has made in
the study of ages anterior to any history.
II.
We need not here repeat the list of
discoveries relative to the age of stone
and to the men of those primitive times.
The savants of the first empire and of
the restoration had denied the existence
of what was then called the fossil man.
Science and religion united in discredit-
ing even the mere possibility. The dis-
cussions which arose when Boucher de
Perthes announced the discovery of the
remains of such a man in the old alluvia
of one of the northern departments,
have not yet been forgotten. His dis-
covery was followed by the sarcasm of
some and the fanaticism of others, until
the day when a new generation of
savants recognized their authenticity.
A short time afterward skeletons of fossil
men and remains of their works were
found on all sides. The name of Lartet
is connected with the exploration of the
caverns of Perigord and Languedoc;
those of Tomsen and Wilson with the
prehistoric antiquities of Denmark; and
that of Keller with the lacustrial habita-
tions of Zurich. Since then Boucher de
Perthes is regarded as the originator of
a new science, which forms the connect-
ing link between the geology and archae-
ology of historic times. This science
though of recent date is always possessed
of a great number of observed facts, is
methodic and well defined, and its gen-
eral results are already perceived.
Among those who concurred in these
first developments there will be found
very few erudite men; they are mostly
scientific men, geologists, physiologists,
engineers, chemists, and perhaps ama-
teurs who delight in this science as a
past time to beguile their leisure hours
THE ORIGIN OF METALLURGY.
505
away. Texts were for a long time the
only means of investigation; but the
most ancient texts are, in reality, mod-
ern, if they are compared with those
long periods of which mankind in its in-
fancy passed over. The most ancient
Grecian authors, those who under the
real or fictitious name of Homer, have
bequeathed the Iliad and Odyssey lived
in the iron age, they related events
which occurred many years before, and
if real, were accomplished, according to
all appearances in the bronze age. This
does not prevent the author of the Iliad,
and especially of the Odyssey to put iron
in the hands of his heroes; thus the
poets attributed to the past what was
before their own eyes, but which the
past never knew. Egypt had not yet be-
gun to furnish those documents which
are now being found; it was not known
that the first four dynasties at least are
anterior to the knowledge of iron in that
country. The hymns of the Veda, to
serve as scientific documents, should in
the first place be classed according to a
chronological order and referred, if pos-
sible, to certain and determinate epochs.
India seems far from being able to throw
any light on this subject. As to Genesis,
it is known that its origin is a matter of
discussion among the learned, and if
some, true to their faith, attribute it to
Moses, others reject its authenticity and
consider it as formed by the union of
two opposed traditions into one book.
Be it as it may, and admitting the au-
thenticity of Genesis, it is at least certain
that its author had little knowledge of
the bronze age, and still less of the stone
age, for it is said that Tubal-cain, the
first metallurgist who is mentioned,
" Was maker of all sorts of instruments
of brass and iron." In fine, the ancient
authors cannot have had correct ideas of
the primitive times, composed perhaps of
decades of years when writing was not
yet in existence. It is possible there
were traditions handed down from year
to year, still the passage from the
Prometheus of Eschylus, in which men-
tion is made of the first men, of their
living in caverns, and of the discovery of
metals, is too vague to serve as a basis
for scientific induction. In fact the
ancients were not in a situation so ad-
vantageous as ours with regard to the
past which there were no documents to
record, as they neither had the means
we possess, the innumerable facts which
all the countries of the world can furnish,
nor the capacity of acting in concert as
now throughout Europe by means of
communication and typography.
The Greeks made no underground
searches. The Romans robbed a great
many tombs, not through love of science,
but to obtain the valuable objects there-
in, which have been reburied or have dis-
appeared with them. The Roman church
which followed the empire has never
favored the positive sciences. The mid-
dle ages were taken up with metallurgy,,
but their end was that of King Midas;
the philosophers stone was to convert all
the metals into gold. The modern spirit
which may properly be called the scien-
tific spirit, after having learned with
Bacon and Descartes its real rudiments
has steadily advanced in a series of dis-
coveries. Possessed of the abstract
sciences it has been able to unite con-
jecture with reality, and found natural
philosophy and chemistry.
It then gave birth to that new study,
whose subject is human beings; to the
physiology of plants, of animals, and
finally to the science of man, of which
prehistoric archeology forms the first
chapter.
Farmers and workmen had for a long
time known of the existence pf instru-
ments of bronze, and had gathered and
sold them before the savants thought of
collecting them and organizing a muse-
um. The first collection made was that
at Copenhagen. It was Thomsen who
as early as 1836, classified all objects
dug from the dolmens, barrows and
mounds of Denmark, and founded the
museum of Northern Antiquities, the
finest prehistoric collection in Europe. A
certain Swede, Sven Nilsson; profiting
by Thomsen's work, and by his own
knowledge of the barbarians of Oceanica
and of other countries not yet civilized,,
united their industrial works with those
of the ancient Danes, and from 1838 to
1843, introduced the study of compara-
tive ethnology. It is not to be supposed
that the savages of to-day are descend-
ants of the ancient inhabitants of
Europe, but their ways of life are the
same, and they make use of the same
means to satisfy their wants. There
now exist colonies which do not know
506
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the use of metals, or which obtain them
in small quantities and look upon them
as objects of personal ornaments; they
have nothing to exchange in commerce
with the rest of the world.
It was Thomsen and Nilsson who
distinguished the stone age from the
bronze age; they had found in the
Northern countries a certain class of
tombs in which, besides skeletons and
rough pottery, objects of stone are
found, but there were no traces of any
metal. In others bronzes were found to
have served the same purposes as stone,
and to have been substituted. In others
again appeared articles of iron almost
similar in form to those of bronze of the
other graves. It is evident that if the
men of the first period had had bronze,
they would have used it in preference to
stone, while those of the second would
have put aside bronze for iron.
Thus the first distinctions of the pre-
historic ages were established and in
succeeding years were confirmed. Two
years after, M. Worsaae, a Dane, in his
book on the ancient times of Denmark,
set to work to explain the numerous
discoveries of the bronze age made in his
country. Notwithstanding this, until
the year 1853 there were but few works
added to the corpus of a science which
seemed to be confined to Northern
Europe. It is but necessary to recall
the memory of Mr. Simon, of Metz,
regarding the discoveries of Vaudrevan-
ges near Sarrelouis; there were found
four hatchets, one mould, one glave, one
horse bit, fourteen bracelets, and many
other small objects all of bronze. It
was a real treasure, but added little new
to the science.
Switzerland ranked next. In 1853
there were found in the lake of Zurich,
and shortly after in the other lakes of
that country, dwellings built on stakes
driven in the ground, which have re-
ceived the name of palqftttes. With this
discovery of great scientific value, we
find the name of Dr. Keller associated.
It confirmed those made in Denmark and
Switzerland ten years previously. These
houses were not situated along-side of
each other, but superposed, and present-
ed the three prehistoric ages. Among
the ruins of the upper layer was found
iron mingled with bronze; in the middle
layers just beneath, bronze only together
with objects of stone which the metal
had not yet replaced; and lastly, in the
lower layers on the bottom of the lake
were found articles of stone only, with-
out any metal whatever. At the same
time the progressive march of civilization
was noticeable by the excellence attained
in the art of moulding either pottery or
metal. There was no longer doubt as to
the succession of ages, nor as to the
essential character of each. The lacus-
trial habitation of Switzerland proved
that these three periods of ancient civili-
zation were not confined to the North,
but were spread in more central coun-
tries.
That same year (1853), was favorable
to the prehistoric sciences. While M.
Keller was sounding the lakes of Switz-
erland, there was discovered at Villanova
near Bologne, a necropolis, which has
been termed, perhaps not entirely cor-
rect, proto-Etruscan. It was examined
and described with exceeding care by
Count Gozzadini, who made it known the
following year, and who has since then
made numerous other discoveries. The
nature of the objects found in that ceme-
try showed that it belonged to a time
posterior to the last period of bronze,
but anterior to the Etruscans, with
whom its dead had till then been con-
founded. It was after the discoveries of
Villanova that the first iron age was
assigned a place in science; this age had
followed the period of transition from
bronze to iron, corresponding to the
upper layer of the palafittes, and had
perhaps immediately preceded the Etrus-
can period, which extended down to his-
torical times. Thus the past and present
of man seem to be connected by a series
of links, so to speak. Archceology is
properly a branch of history, and is
probably the most substantial part, as it
is founded on real facts and not on mere
reports often altered and sometimes falsi-
fied. Its commencement is connected
with prehistoric studies, as the three
prehistoric ages are connected two by
two in their order of succession. In
ascending from age to age, you arrive at
the period of unpolished stone; beyond
that there is probably a long term of
years ending with a man of the quater-
nary, may be of the tertiary period;
that is to to say, with the geological
epochs prior to the one in which we live.
THE ORIGIN OF METALLURGY.
507
It is at this stage of science that theories
begin, as those of Darwin on the origin
of the human species, and its animal
Romer; in Ireland, Wild; in Russia,
Aspelm and Bogdanof; in England,
Evans, Franks, J. Lubbock. In France,
forms which have preceded and followed we have already mentioned M. de
Mortillet who is at the head; to this
name we must add those of Messrs A.
Bertrand, Costa de Beaurregard, Cazalio
de Fonduce, l'Abbe' Bourgeons, and M.
Chantre from which we have derived
it.
In 1857, M. Troy on, in publishing the
discoveries of Keller, called attention to
the problem regarding the origin of
bronze; but to solve it, it was necessary
that a science as yet of recent date j much of our information,
should be further developed by new i In 1862, Napoleon III founded the
facts, and throughout many countries. ! Museum of St. Germain, which was es-
After Switzerland Savoy and Italy made j tablished for the purpose of collecting
the largest contributions to the study. I the Gallo-Roman antiquities; the history
Professor Desor the following year i of the Caesars, in connection there-
sounded the waters in lake Neufchatel, j with, became a study of especial in-
and after M. Morlot had, in 1860, pub
lished in Switzerland the discoveries
made in Denmark and Sweden, a
spirit of searching was manifested
throughout the central countries. Messrs,
terest to the Emperor. The director
was not slow in enlarging his plan and
obtaining more help, and was soon able
to offer to the public a prehistoric museum
which well compared with the one at
Fastaldi and Desor that same year visited | Copenhagen. It is to be regretted that
the lakes of Lombardy and found in the I a collection of this kind is 20 kilometers
tour bieres of the major lake objects ; distant from Paris, which makes it in-
s'imilar to those in the lakes of Sweden, j convenient for the public; and the scien-
In lake Varesa, in 1863, Messrs. de tists do not derive the benefit they
Mortillet, Desor and Stopani recognized ought, so that it is not frequented very
the period of transition from the age of j much.
stone to that of bronze. The palafittes : Two years following M. De Mortillet
were noticed only in later years around , commenced the publication of his
the fortress of Peschiera. "Materiaux pour servir a Phistoire de
Since 1862, Messrs. Strobe] and Pigo- l'homme," a work of great interest
rini have found not far from Parma, de- ! which, in 1869, passed into the hands of
posits of loam, known to husbandmen as ! M. de Cartaihoe. Since 1865, on the
terramares, and therein detected the | suggestion of M. de Mortillet, there was
remains of the old lacustrial habitations; started an ethnological congress which
in fact the stakes still remained, and i is composed of the savants of Europe;
were surrounded by organic matter; i this congress changes its place of meet-
from the appearance of the alluvium it | ing from time to time, and has already
was evident that water had remained in assembled, besides at Spezzia where it
the low portions of Emile, and that ! originated, at Neufchatel, Norwich,
formerly there had flourished a civiliza- j Copenhagen, Bologne, Brussels, Stock-
tion identical to those of the Swiss [ holm and Pesth; they propose holding
lakes. i their next sessions at Athens, Smyrna or
We cannot here cite the names of all ' Constantinople,
those who, since 1860, have contributed j The impetus given to the prehistoric
to the advancement of prehistoric studies, studies by these three French institutions,
their number has increased in proportion
as the increasing interest of research ex-
tended, and a method of procedure was
adopted.
Suffice it to say that searches were
was increased by the universal Exposi-
tion of 1867, where a number of the pro-
ducts of primitive industry was gathered
together. The Exhibition of 1878 will
be still more important as it is intended
made throughout Europe, and that the j to bring together entire collections from
desire to contribute to the progress of j all countries. Germany alone will not
the science of man, has called forth j be represented.
many exploring savants throughout j The number of books and memoirs
western Europe. In Austria, there were j relative to the ancient ages and particu-
Eam--auer and de Sasken; in Hungary, | larly to the bronze age, is considerable.
508
VAN nosteand's engineeking magazine.
There are very many public and private
libraries throughout Europe, so that it is
next to impossible for one man to visit
them without devoting much time and
money. The need of statistics, as full as
possible to give all the learning available
to aid in future discoveries, was felt.
The demand was supplied by M. E.
Chantre's admirable work entitled the
Bronze Age. In one of the three vol-
umes of which it is composed, there are
only tables in which are classed in
methodic order, all the objects of the
bronze age found in France and Switzer-
land with indications of their orgin and
where they can be seen to-day; there
are at present almost 33,000 specimens.
The other volumes contain much infor-
mation of the other parts of Europe
from which objects of bronze were
gathered. If a work similar to that of
M. Chantre was devoted to each of
them, it might be easily believed that
the conclusions of this savant would be
confirmed, as they are founded on a
thorough knowledge of all European
collections, although his original inten-
tion was to have merely given statistics.
As no work of this kind had yet been
published on the prehistoric ages, it is to
be expected that this one will form an
epoch in the science and will be a start-
ing point for new discoveries to begin.
III.
We will now speak of the places where
products of bronze industry were found.
The first steps of science were difficult
and uncertain, because discoveries were
made by mere chance, and by inexperi-
enced men, who very often sold their
antiquities by the weight, and sometimes
destroyed them even. Thus in 1859 on
a farm of M. deGourgue near Bordeaux,
" the husbandmen on returning from the
fields, told their master that during the
day they had found a corpse, that they
tried to smash its head with their sabots,
but it was so big and hard that they
could succeed only with their spades."
They brought back with them however,
a hatchet, a sword, golden threads and
fragments of pottery. The following
occurred in 1865 at the celebrated pre-
historic foundry of Larnaud (Jura),
"Brenot fils, while digging potatoes,
discovered a piece of green metal which
excited his curiosity and that of his
friends. They set to work and found a
quantity of objects of the same metal
within a plot one meter square. The
next day Brenot pere took a specimen to
Lons-le-Saulnier, a brazier, who told him
that the bronze was worth forty
cents a kilogramme. On this man's sug-
gestion, Brenot offered his treasure trove
to an amateur of antiquities, M. Z.
Robert,' who did not hesitate to take
them. There were about eighteen
hundred pieces, weighing 66j kilogram-
mes." All this bronze came near being
! thrown into the crucible of the founder.
' It is now in the museum St. Germain,
i and is one of the most interesting col-
! lections. One more incident may be
I given. The ancient foundry of Vernai-
son (Rhone) was found in 1856 on the
property of M. D . The total weight
of the bronze was 16 kilogrammes, but
the director of the Lyons Museum at
that time, retained only a small portion.
"We have selected," said he, "the
complete, or mutilated objects most
worthy, to adorn the museum, the rest
was returned to M. D. — , who proposes
to have cast a commemorative urn, with .
an inscription recalling the event of the
discovery." Notwithstanding the dan-
gers by which the prehistoric science
was surrounded, the bronzes in France
and Savoy are already so numerous and
so well characterized, that M. E. Chantre
has been able to class them into categories
which we divide in two groups; the
visible strata, and the hidden strata.
The first comprises grottoes, dolmens
and palafittes or lacustrial habitations;
the second, treasures, foundries, isolated
stations and tombs in open fields.
It is well known that caves formed
the first habitations of man, not only
during the stone, but also the bronze
age. Throughout Europe inhabited
caves are found. The most interesting
perhaps, are those of Central France
and on the banks of the Meuse. The
latter have the advantage of being in
three planes, representing three succes-
sive risings of the river which irrigated
its banks. They present supposed layers
of human remains of three consecutive
epochs; that of metal, of polished stone,
and of rough stone. The latter which is
beneath the other two, is no longer
found on a level with the other two
layers which were then beneath the
THE ORIGIN OF METALLURGY.
509
water, for the Meuse at Dinant was not
less than three leagues wide. Among
the human remains there are bones of
mammoths, hyenas, rein-deer, animals
which were then in France and Belgium.
The inhabitants of the caves made
earthen vases, but knew not the art of
baking them, although they had fires.
M. Dupont, (L'homme pendant l'age
de la pierre) from whom the following is
obtained, estimates that during the
period of the mammoths, the width of
the Meuse at Dinant decreased from 12
kilometers to 400 meters, which is the
distance of the caves in the center.
To-day it is but thirty meters. The
middle layers just beneath those of the
mammoth, correspond to the period of
the rein-deer, the grottoes, which are
termed pits of the Mitons, of Chateaux,
of Frontal, are striking examples. The
remains of human industry are buried
beneath a bed of yellow clay which
covers them. In these no bones of
mammoths or hyenas are found, but
only those of some species now living;
the wolf, fox, deer, wild goat and rein-
deer. There are not yet any polished
stones; there is no trace of metals; the
potteries are made by hand but are
not baked; small stones, pieces of bone,
teeth of animals, or fossil shells with
holes, composed the ornaments of those
people. The third layer, corresponding
to the inferior caverns on the borders of
the Meuse, is that of polished stone; it
is the epoch of dolmens and lacustriai
cities of Switzerland, Savoy and Italy.
Yellow clay disappears, the rein-deer,
elk, wild bull, and castor have all disap-
peared. The hatchets are made of pol-
ished stones with holes for inserting
handles; the potteries are now baked.
This epoch has left behind but little
remains in caverns, but much is found in
the earth of the fields. It is here that
bronze makes its first appearance, and
though scarce in Belgium, is found in
great quantities in Central Countries.'
The caves of the bronze age in France
and Savoy are of two kinds, those used
as dwellings and those, whether natural
or artificial, for sepulchral purposes. As
on the Meuse, the inhabited pits of the
middle states are found along rivers, and
belong generally to the period of transi-
tion from polished stone to bronze.
They are scarce, and among the most
important are those of Saint Saturnin, a
large neolithic station above Chambery,
those of Savigny near Albano, of la Sal-
ette, and of Louvaresse (Iseria). The
people of the neolithic period who wit-
nessed the arrival of bronze inhabited
the plains, and often the borders of
rivers. The banks of the Saone furnish
us with many stations, of which the suc-
cessive epochs appear in superposed
layers; it is especially at the confluence
of streams and about fords that they
may be perceived.
Where the waters were tranquil, and
produced but few changes, that is to say,
near the lakes, the men of that period no
longer used caves. They deserted terra
firma and built houses above water,
resting on piles. None are seen on the
steep banks of lakes as the water is there
too deep, but they are found on shallow
banks of sand or earth where the water
is not profound, as in fords of rivers.
What could have induced those men to
isolate themselves in the middle of these
lakes ? We have not yet learned, but it
is to be hoped that new observations
will solve the problem. However it may
be, we perceive that this custom lasted a
long while, as the palafittes of the Alps
comprise not only the epoch of bronze,
but those which had preceded it, and
those also which mark the arrival' of iron.
There are palafittes of the stone age at the
lake of Zurich, of the bronze age at
Limau, of the iron age at Neufchatel,
and each of these periods is well charac-
terized. There are certain lacustriai
habitations belonging to the two periods
of transition which mark the beginning
and end of the bronze age, so that it is at
least certain that the custom of living
over water, continued without interrup-
tion for a long time.
As there were found habitations built
on piles in the north and center of Italy, it
would be interesting to explore the lakes
of Central Europe, of Greece and Asia
minor, and determine how far the custom
extended.
The men of the stone age consecrated
natural grottoes for burial purposes,
while they also made use of caves as
dwellings. Thus on the Meuse, the small
cave of Frontal was used as*a cemetry
for the men who dwelt in the cave of the
Noutons. This mode of living was still
existing at the appearance of bronze.
510
VAN nostrand's engineering magazine.
This is proved by the " Grotte des Morts"
near Sauve (Gard). Since 1795 d'Hombre
Firmas had called the attention of geo-
logists to this cave, but it was examined
only in 1869. M. Tessier died during
the first clearing out, which was after-
wards accomplished in the name of the
Scientific Society of Alais by Messrs.
Cazalis de Fondouce and Oilier de Mari-
chard. The cave is a sort of vertical
well dug out by nature in a crevice of
inferior lias. From this there have been
dug a large number of bones of men,
foxes, wolves, wild boars, horses, sheep,
a complete funeral accoutrement, com-
posed of arms and tools of silex, bom, or
deer's horn; a quantity of jet jewelry or
of black or green marble, spath and
Alabaster, an awl of bronze and many
iron pearls, many of which were left be-
hind with the rubbish. We will also
mention among the natural caves of the
first bronze period those of Labry and
Baniere (Jard) which have brought to
light objects similar to those already
found, besides a poignard, ear-rings and
bracelets of bronze, and the caves of
Gonfaron and Chateau double (Var).
That of Saint Jean d'Alcas (Aveyron)
discovered in 1838, was searched in 1865
by M. Gazalio. It is partly artificial.
At the entrance there had been placed
two large arched stones supporting the
roof and forming a triangular entrance.
One unfortunately has been taken away
by the owner of the cave, and used as a
door-step to his kiln. Among the nu-
merous objects thrown o'ut with the dirt
by the same person, there have been
picked, mingled with bones and silex,
two hatchets of polished stone, pearls, a
spiral and bronze ring. *
The artificial sepulchral grottoes have
received the name of covered alleys
(alees convertes). They are especially
found in Provence, dug out of the small
calcarlous masonry-works which appear
as islets in the fertile plains of Aries.
They consist of an oval gallery open
above; the walls are inclined towards
each other; the top being covered with
large flat stones which must, in the first
place, have been covered with earth.
One of them, the Grotto of Cordes,
which is also called the grotto of fairies
was in turn supposed to be a Gallo-
Roman cave, a Saracen prison, a Druidic
monument, and, lastly, a sepulchral
Grotto of Asiatic or Phoenician origin.
"You first of all descend" says Mr.
Cazalis, " on large rough stairs into a
fore court, uncovered at present, which
is in the shape of a sword; from thence
you proceed, through a gallery six
meters long, into the cave proper. At
the mouth it is 3.80 meters wide but
narrows in the rear; the walls are sloping.
This trench, which is twenty-four metres
long, is covered by inclined stones and
the whole covered by a tumulus which
is much worn. The total length is not
less than 54 meters." Unfortunately,
the funeral outfits of this cave were
j scattered, so that the epoch cannot be
i determined, except by its resemblance to*
I the Grotto of Castelet in the neighbor-
| hood. The latter contained sixty centi-
meters (2.6634 inches) of earth and
gravel, brought, to all appearances,
from Gardori. On this lay the bones of
about ten men, together with instruments
of silex and bronze, and a saucer of pot-
tery made by hand. For a long time Dol-
mens were looked upon as Druidic altars,
a vague term which with the words
"Celtic" and " Gallo-Roman " is indis-
criminately used. Since they have been
found, not only in Western Europe, but
throughout the whole Continent, Africa
and Asia, new theories have been cur-
rent. Some scientists have looked upon
them as spontaneous transformations
from caves; others thought they recog-
nized, from their distribution over the
old Continent, the migrations of a
wandering tribe, which, driven from
Central Asia, would have followed the
Baltic, stopping in Scandinavia, and
which would then, driven from the
Northern countries, England and Ire-
land, arrive in Gaul, then proceed to
Portugal, and finally to Africa. We do
not suppose that dolmens have as yet
been the subject of sufficient observation
in Africa and throughout Asia, nor even
in the different parts of Europe, that any
theory should already be substantiated.
The monuments which have received
the appellation of megalithic, nearly all
belong to the period of polished stone;
still a large number date from the
appearance of bronze. Those of the
North are generally the oldest; and if
we may judge of their relative dates by
the quantity and quality of bronze
which has been obtained, their antiquity
THE ORIGIN OF METALLURGY.
511
diminishes in proportion as you descend
from North to South. This does not
prove however, that dolmens originated
with a race descended from the Northern
countries; it would on the contrary indi-
cate that bronze brought from the Medi-
terranean countries, reached the North
only by slow degrees. There are 147
dolmens in the South of France in which
bronze has been found: they are mostly
situated in the region of Cevennes, a
short distance from the Mediterranean.
Several dolmens from Marne and the
environs of Neufchatel have also yielded
some. Those of Bretagne, with the
exception of a few in which a little
metal was found, belong to the neolithic
period. The 147 dolmens in which
bronze was found mingled with objects
of stone, pottery of the second period
and other objects which will be mention-
ed further on, form but a minority of the
great number which have been explored.
In the South of France alone, 700 have
been opened in Ardeche, 300 in Avey-
ron, 160 in Lozere. It may be taken for
granted, that if all belong to the period
of polished stone, the people who built
them witnessed the arrival, in small
quantities perhaps, of the first common
metal. If they had had it in abundance,
they would in all probability have made
arms, instruments and even ornaments of
bronze instead of stone, shell, horn, or
bone, for with a silicious saw they could
accomplish in one day of hard labor,
what with a bronze saw they could do in
an hour, with an iron saw in a few
minutes, and in a few seconds with a
steel saw impelled by mechanical force.
Let us suppose it is yet the custom to
bury with a person the objects he has
used during his life time, and that in five
or six thousand years our graves should
be opened, many circular saws would be
found in England, France, Switzerland,
Germany, but few in Italy, especially to-
wards the South, still fewer in Spain,
one or two in Greece, and not one per-
haps throughout European and Asiatic
Turkey. We do not, however, notice
any migrations in our midst; the indus-
tries themselves are propagated, but the
people do not migrate; a few men pass-
ing from one country to another suffice
to introduce new industries. The com-
position of dolmens is uniform, only that
bronze increases from North to South;
it seems then that there existed in the
Mediterranean regions, or beyond, a
country from which bronze is brought
and distributed through the Northwest
of Europe.
We must now speak, from the numer-
ous facts collected and classed by M.
Ch autre, of the beds of bronze which
were hidden under ground, and brought
to light by mere chance. They are of
two kinds; the foundries and the trksors^
to which may be added certain stations
or centers of habitation as yet not well
classified, and a number of tombs in open
fields, whose presence there is nothing to
indicate. A foundry consists ordinarily
of a mere cavity dug out of the earth,
and contains more or less complete the
materials of a bronze-founder; ingots of
metal, refuse and waste metal, ashes,,
fragments of things of little value or
worn out, or defective, and, finally, cru-
cibles, moulds, pincers, and sometimes
even new objects coming out of the
moulds and incomplete. Many of such
foundries have been discovered in parts
of Europe, especially in Fiance, Savoy
and Germany. Should the place and
statistics of each be desired, I would re-
fer the reader to the book above cited.
The foundry of Larnaud may serve as a
specimen. I have already stated how
the son of Brenot the farmer, discovered
it in 1865, and how, when offered by his
father to a brazier of Lons-le-Saulnier it
was saved by M. Zephirin Robert. After
having been exhibited during the Expo-
sition of 1867, in a store on the Boule-
vard des Filles du Calvaire, it was
bought for the Museum of Saint-Germain.
The case in which it is exhibited has
been classified and labeled by M.
Chantre who, in his work, gives a cata-
logue and full description. The value of
the collection obtained from Larnaud, con-
sists in this, that all the pieces which com-
pose it are contemporaneous : there are
1485 such pieces, and the epoch to which
they belong is evidently the end of the
bronze age. This is what is shown by a
comparison with those of the other
foundries, and especially with the objects
obtained from the pakfittes of Savoy.
Throughout, the last epoch of bronze is
characterized by traces of the hammer,
by the presence of metallic plates or
leaves obtained by concussion and not
merely by casting. On the other hand,
512
VAN nostrand' s engineering magazine.
that which links the workshop of Larnaud
with the age when bronze was the only
common metal are the cold chisels made
of hard bronze to cut bronze, as steel
cuts iron. But since bronze is softer
than iron, can it be doubted that cold
chisels would have been made of iron, if
the latter metal had been known or was
at least abundant ? We will give
further proofs showing more clearly the
epoch to which we must refer the foundry
of Larnaud.
There are other foundries belonging to
this period, among which we will men-
tion that of Poype, situated on the
heights overlooking the Rhone to the
South of Vienna. A portion of the
bronze had been sold to a merchant of
Lyons, at the price of old brass; it was
bought by M. Chantre who, on precise
indications, renewed the search and was
able to duplicate the products. The
foundry of Goncelin is also situated on
the heights adjoining the Iser, as well as
those of Thoduse and Bressieuse. The
largest portion of the other stations of
this kind are in the neighborhood of
rivers, and probably at a short distance
from the places then inhabited. What
is probably the most remarkable is their
uniformity throughout Europe. They
indicate, to all appearances, the passage
or stay, long or short, of workmen be-
longing to the same class, but who were
not natives. Foundries are, in fact, al-
ways found in isolated spots, but no
traces of human habitations are seen. It
is true that habitations may disappear,
wooden houses crumble into dust, and the
very stones become, in the course of
time, dispersed and used elsewhere.
There is, at any rate, one product of
human industry which never disappears,
and attests the presence of man during
the most ancient times; that is the
baked clay and especially broken pottery.
Its tenacity is such, that on closely com-
paring the soil with some of the frag-
ments, it is often easy to determine the
place and size of cities which have dis-
appeared several centuries ago. The
neolithic foundries are never surrounded
by such ruins.
There are but few lacustrial habita-
tions where the metals were wrought,
but here the natives might have been
taught by travelers. The initiation
seems, in fact, probable, from the exist-
ence of certain inhabited spots, which
are called stations. Those which are
known are not very extensive; in most
cases they are on a line with rivers, as
may be seen, for example, on the banks
of the Saone between Chalons and
Tournus; still there are some isolated
ones. The most important of them all
is that of Saint-Pierre-en-Chastre in the
forest of Compiegne. It is situated on
the calcareous plateau in the swampy
plains of Vieux-Moulin. It was dng by
M. Viollet-le-Duc in 1860, and yielded,
among other things, more than five
hundred bronzes, which are indistinctly
attributed to Gaelic armies. Since then,
science having made some progress, they
have found that it is necessary to dis-
tinguish the objects of stone, bronze, or
iron obtained in that locality; that all
was anterior to the time of Caesar; that
there were few arms; that the quality of
bronze was identical to that of the other
layers of that age throughout Europe.
On close examination, comparisons
showed that the station of Saint-Pierre
had probably existed for several centu-
ries, and that it had witnessed if not the
first appearance of bronze in that coun-
try, at least the epoch of that metal, and
the commencement of the iron age.
But the interest in the stations is, in
part, lost in that of the tresors, as these
seem to demonstrate the reality of the
traveling founders; the idea merely be-
ing suggested by the foundries. The
most important were found in the Alps
on the neck of the mountains, some near
Moulin s and Gannat, two in Meusth, and
one near Sarrelouis; there are altogether
twenty-nine in France, comprising up-
wards of 1350 pieces.
These treasures are composed of new
objects, never having been used; some-
times several are joined together having
been cast in the same mould.
They are found in small cavities ex-
pressly dug, where they seem to have
been hidden for a short time by their
possessors. These treasures, those of
the Alps at least, are often found on
high ground, not far from roads, fre-
quented by travelers going from one
country to another. There are no signs
of a foundry in the vicinity, or even of
a station, the spots where they were
found are deserts. Is there anything
to be found in these temporary deposits
THE ORIGIN OF METALLURGY.
513
besides objects of traffic ? Were they
not hidden by the same men who, in the
valleys, recast the inferior products of
their own industry ? If all this leads us
to believe that such is the origin of the
these several specimens have been ex-
tracted from the lakes of Savoy, such as
spoons, tool handles, spindle shanks,
sabots, a porringer, and part of a bucket.
The great number of bobbins of baked
treasures, there would only have to be | clay which are called by the Italians
determined the direction in which these \fusaioles, indicate that the custom of
workmen went, to know whether they ! spinning and weaving was then extant;
came from Italy to France, or vice- versa.
It will directly be seen that this difficult
problem is no longer insoluble to-day.
there were many discussions as to the
use of those small cones bored through
their axis, but there is now no more
The treasure of Reallon, which is | doubt, since a complete spindle was
now in the museum of Saint Germain, I found in the lake of Bourget. We have
was found in that village not far from | ourselves seen pieces of wood worn out
Embrun 3880 meters high. "This road,
anciently frequented by foot- travelers,
leads from Saint Bonnet to Embrun, by
in the holes of many bobbins, found in
Troy by Dr. Schleimann.
These very things are still used
Gociere." The treasure of Beauviears j throughout the Middle and West of
was found by a farmer. This village of
the arrondissement of Die is situated on
an ancient passage of the mountains, on
the peak of Calre, on the road to Luc.
There were many other valuables which
Europe. They could obtain very deli-
cate threads with these spindles of wood
and clay, as is evident from the small-
ness of the eye of several bronze needles.
The finest textures have been destroyed
had been stowed away on the upper under water as well as under ground,
banks of rivers, as well as on the plains, but a few specimens of the coarser tex-
Tv j tures, meshes of nets, thread, cord, and
j bundles of beaten flax, have been pre-
We must now speak of the industries j served in the mud of the palafittes of
of the bronze age of which the several ; Bourget. The flax then used had small
strata compared with each other have i leaves, and differed from the kind now
revealed the existence, nature, processes \ cultivated. To the weaving we may
and relative epochs; among them there
were some indigenous. Undoubtedly
the men of those ancient times must
have built their own houses, which were
made of wood, after the time they left
the caves. Those they erected on solid
ground have disappeared without leav-
ing any traces behind; and if the houses
of the lakes have been destroyed, at
least the piles upon which they were
add the fabrication of baskets of rushes,
reeds and osier, and the making of fish-
ermen's snares, and the large hurdles
which were used to fortify the walls of
houses in supporting the roof.
The local industry which has left the
most traces in the strata of bronze,
except the treasures and foundries, is the
moulding of argil. We have already
noticed that the potteries of the periods
built still remain. Those of the epochs I of stone were not baked, but merely
anterior to metal, were nearer the banks j dried in the sun. The art of baking was
and did not project so far out of the j introduced during the age of polished
water. The others were built beyond j stone, and continued to be improved
the first, and in Savoy, have a greater during the entire age of bronze. Still
jutting out, by which they can easily be | the most ancient vases of that period
recognized. The pieces of wood resting I were badly baked, very often burnt on
on the piles and forming the flooring, one side and raw on the other; it would
were fastened together by means of seem that these potteries were cooked in
tenons and mortises; which shows clear- the open fire and not under a reverber-
ly that they could with hatchets and | ated furnace, which however was the
chisels of stone, cut and shape large \ case. The dishes and plates showed few
pieces of wood. Planks were made by j signs of the fire. It was only towards
splitting the trunks of trees; the stone | the end of the bronze age when iron was
saws are only several inches long, while ' already beginning to supplant it, that
those of bronze are not a foot; they : the potter's wheel was used. As simple
could only be used on light work. Of | as was this revolving machine, it afforded
Vol. XIX.— No. 6—33
514
VAN NOSTRAND'S ENGINEERING MAGAZINE.
certain facilities of fabrication which
were formerly unknown. The progress
seems to have been made only after the
appearance of iron. The various kinds
of vases fabricated by processes so ele-
mentary were astonishing. Some were
used for carrying water, others for pre-
serving and cooking food. There were
also some drinking vases, among which
are the rhytons, and lamps in imitation
of the old Greek and Roman lamps,
rings of clay used as rests for small-cased
vases and peforated cheese molds as in
our own day, which shows that men in
olden times were fond of the product of
the dairy.
With regard to the ornamentation of
pottery, it has received special attention
from scientists, for it has afforded, during
the bronze age, transformations useful in
chronology, which are found on con-
temporaneous bronzes. The rough pot-
tery of the stone age was ornamented
by straight lines engraved thereon with
zig-zags more or less irregular. In
course of time these lines became more
regular, and are drawn parallel by means
of burins with several points, conse-
quently the figures are more accurately
made. The use of concentric rings may
be noticed throughout Europe during
the bronze epochs. The plain cross, the
multiple and four pointed cross, the
encircled cross in shape of a wheel, stars
and triangles appear regularly in succes-
sive years.
The figures are no longer merely
engraved with pointed instruments, they
are also impressed with stamps of metal,
clay, or stone. The Swastika (a species
of cross with curved arms) and the me-
and re which is made up of a succession
of swastikas, are to be met with especially
during the period of transition from
bronze to iron. During the first iron
age, and further on in historic times,
this figure was popular with the people
of the Aryan race, and appeared in the
west after the bronze ear. It was about
this time that the potters began to paint
certain vases with red or yellow ochre or
with that black which afterwards became
peculiar to Grecian ceramics. Lastly,
the inhabitants of the lacustrial dwell-
ings used a sort of decoration which
was, however, afterwards abandoned.
On the dark bottom of some vases of
fine clay, they fastened thin sheets of
pewter cut in narrow strips, with rosin?
and formed a variety of beautiful designs*
Metallic ornamentation, no doubt, had
its origin in the West. The industry of
bronze characterizes the period now un-
der consideration. In speaking of the
foundries we made little mention of the
material of the founders; so far there
has been found but a small piece of
mineral brass, and nowhere in Europe
has a furnace or any instrument for ex-
tracting ore been found. We may, there-
fore, be justified in supposing that the
metal was brought from the vicinity in
its rough state, or already molded. In
fact, ingots of bronze are found wher-
ever the founders were stationed, they
are in the form of small squares, or like
hammers having a hole in the center to
hang them up by.
We should recollect that no pure cop-
per* is found, very little tin, whilst
throughout Europe bronze is of uniform
composition. The following is obtained
from the analysis made by Messrs.
Wibel and Fellenberg and by M. Dam-
our; the proportion of tin is about
ten per cent., but there are exceptions as
in cold chisels and one or two other ob-
jects of hard bronze, which contain as
much as a quarter of tin to three
quarters copper. This uniformity of
composition of alloy throughout Europe,
proves the unity of its origin and im-
portation, but of this further on.
Researches have brought to light be-
sides ingots and refuse castings of metal^
a number of molds made of schist, stea-
sheist, free-stone, baked clay and bronze.
Many of these have figures on two or
four sides, and on some there are several
figures along side of each other. The
crucibles are made of earth mixed with
broken quartz and often contain metal.
Some have the shape of the laboratory
crucible, while others are like cups with
handles. All these receptacles could
contain but a small quantity of metal;
their form and dimensions are pretty
much the same throughout Europe.
The articles, made by means so rudi-
mentary, may be divided into three
classes, viz., tools and utensils, arms and
ornaments. Among the first may be in-
cluded the hatchets first made similar to
stone hatchets, with holes for the pur-
* It appears that in Hungary and Greece many speci-
mens have been noted.
THE ORIGIN OF METALLURGY.
515
pose of inserting a handle which was
fastened in the socket with a cord. We
are able, considering the superposition
of the layers in the lacustrial habitations
and stations to follow these transforma- j
tions, and determine their relative epochs, j
Scissors, knives, chisels, sickles, handles, I
saws, gimlets, jewelers' pincers, are the j
tools usually found in all the strata, j
We may also add razors which were ;
first made of hard stone, then of bronze, j
which are finally supplanted by iron i
ones. These instruments were not of ;
the same shape as they are to-day; they I
were semi-circular with the edge on the
side of the curve. Then there were some j
double ones edged on both sides of their j
diameter, and fastened to an ornamented j
handle, forming together but one piece, j
The different razors will enable us to as- j
certain the relative age of the strata in |
which they are found.
Was the horse domesticated at the ap- 1
pearance of bronze ? It is probable that ;
he was tamed during the period of
polished stone, and yet it is possible he i
may have been long before. If he was
then only in a wild state, it would be
difficult to explain the quantity of bones
which are found in certain places of the
first period of stone as in Polutre. This i
station which is not far from the Saone j
river, above Macon, contains, it is said, |
the skeletons of 100,000 horses, most of j
them young, which may have served as j
food for the inhabitants of the place.
Be it as it may, the bronze bits found
among the piles of the lake of Briene
and afterwards in France, bear witness to ]
the fact that the horse was already sub- 1
dued. The oldest of these bits are made j
of two moveable pieces one above the \
other in the center of the animal's mouth, j
Soon after the four pieces are movable, |
although each of the exterior pieces has j
a cross-piece through the middle, and I
thus forming two equal branches. This !
second class of bit characterize the terra- i
mares, and had been learnedly studied by !
Count Gozzadina. It seems that in the j
stone age the horse half tamed was used !
as food for man, that being subdued in I
the second period he was mounted and j
perhaps harnessed, and, finally, at least in
Italy at the end of the bronze age he be-
came tame enough to be guided about
with a string. Arms do not form the
least interesting portion of our bronze
collection; they perhaps better than any-
thing else enable us to determine the
successive phases of this metal. They
are found everywhere in Europe and
Asia, but they should not be attributed
to Gaul as has been done. The palafittes,
foundries and treasures have given them
their definitive place in the bronze age,
and if they appear only in small quanti-
ties owing to the scarcity of the metal?
they soon become so abundant as to sup-
plant entirely the arms of stone. Later
on iron is found in many places in
Europe, but in small quantities and is re-
garded as an object of luxury. It soon
after exercises in its turn an appreciable
influence on bronze arms, the form and
size of which are modified. Finally,
bronze is entirely abandoned. The blade
of the swords and poignards of the early
part of the bronze age was of metal, but
not the handles. Often in these primi-
tive arms, the tongue of the blade does
not go far into the handle; it is broad
short and pierced with two or more holes
through which the iron rivets pass.
Afterwards metal handles are made,
either without a guard or one in the
shape of a cross. Switzerland, Denmark
and Sweden have produced swords with
antennae, that is to say, with two prongs
jutting out and curved at the end of the
handle above the hand. The long
swords, the length of which is often two
feet and a half, which are to be found
throughout the West, had handles made
of horn, wood and bone, and resembled
the iron sword which soon replaced them.
In France there have been discovered
650 swords and poignards of bronze, in
Switzerland 86; in Sweden 480, and are
generally found throughout Europe.
The dolmens and sepulchral caves of
Lauguedoc and Vivarais, the palafittes
of the lakes of Neufchatel and Varesa,
have produced arrow heads similar to
those of silex which had preceded them,
and used up to the transition from stone
to metal; they characterize this epoch as
the razor characterize the transition of
bronze to iron. These small pieces of
metal were flat, being fastened in the
shaft with a cord.
It is during the second period of the
bronze age that armor is made of
metal, as helmets, shields and cuirasses:
prior to this time they are made of
leather and wood. This is the period
516
VAN NOSTRAND'S ENGINEERING MAGAZINE.
that M. de Mortillet designated by the
term " Chandronnerie," the art of en-
larging and shaping iron under the
hammer, being added to that of mold-
ing. This method was used not only in
the manufacture of armory, but also to
the edging of arms and tools and of a
multitude of ornamental objects.
The latter outnumbered the former,
especially when metal was rare; pins are
picked up by hundreds. The foundry
of Larnaud has furnished 214 bracelets,
the lake of Bourget more than 600, and
a great number have been found in the
dolmens of Central Europe. The oldest
are oval, the latest are round; those
which date from the bronze epoch are
open, but are closed as soon as the
industry of iron is general. The large
collar rings, called torques by the
Romans, is not found until after the
appearance of the latter metal; finger
rings are scarce throughout Europe, but
plain rings, necklaces and buckles, are
everywhere found in large quantities;
there are besides these many other orna-
ments or amulets, such as ear-rings,
fillets, &c, which evidently have a
symbolic character. Let us here note
that these symbolic figures are about the
only signs of any religion during the
bronze epoch. We may add that they
are not indigenous, but are doubtless
derived from Asia, as also the cithern
which is made of hollow reeds with nine or
twelve rings fastened at the end of a
stalk of wood. There are several in
existence, two of which were found in
France, three in the lake of Bourget, the
others at Christiana, at Wladimir and
Yavorlan. These citherns are not like
those of Egypt, but like those of the
priests of Buddha, who themselves hold
them of an ancient Aryan tradition.
We have just placed before our read-
ers the general conditions of the problem
relative to the origin of metallurgy in
Europe.
From the facts which have been brief-
ly stated, but may be found enumerated
and more fully described in M. Chanter's
great work, and especially after seeing
the objects themselves in our museums,
they will satisfy themselves that the
problem is henceforth well sustained,
that the method of proceeding is deter-
mined, that the researches of primitive
bronze and the scrupulous examinations
of the strata in which it is found are the
principal if not the only means to arrive
at a solution, and that finally the accu-
mulated works of many learned men
throughout Europe have already given
to science a large and solid foundation.
This immense work which we have con-
densed in a few pages was begun about
forty years ago, but has been generally
known only within the last twenty
years.
Europe has not yet exhausted itself,
still we feel that the origin of metallurgy
must be sought for outside of its
frontiers. When warriors will give a
little respite to science, the East of
Europe and Asia will become the scene
of scientific discoveries; in fact, the
first appearance of the metals must be
sought for in the Southeastern portion
of Asia. Still to be certain of the fact,
we should, by investigations analogous
to those made in Europe for the last
twenty years, to a certain extent trace
the routes which the industry and com-
merce of the metals have pursued.
These routes, at least with regard to
bronze, will converge no doubt towards
one point. If Central India and Tartary
had simultaneously furnished this metal,
we would see in all the collections of
Europe two different types and, probably,
two different alloys in objects of the
same kind; but the converse is true.
Except the local differences arising in
different ages, the products are the same
throughout the West, from Sicily to the
Northernmost of Sweden and Russia.
The composition of bronze obtained
from a number of analyses in which the
approximation was to a ten-thousandth
part, is the same everywhere; the scien-
tific processes are identical. The three
successive epochs of the bronze age is
everywhere perceived; first, wherein it
is seldom found amid a people occupied
in polishing stone ; second, wherein
metal has definitively replaced the latter
in certain usages when decidedly superi-
or, and lastly, wherein bronze concurs
with a new metal, iron, which eventually
supplants it. Such a uniformity at a
time when there were no roads and no
protection, when the races which inhab-
ited Europe had not yet mingled and
experienced their respective wants, and
THE ORIGIN OF METALLURGY.
517
had their own special trades; in fine, the
absence of tin in Europe except in
Cornouailles, as well as native copper,
are sufficient reasons to lead us to believe
in the foreign origin of metallurgy.
To arrive at a starting point we could
at present proceed by elimination and
show that neither Northern Asia, Cauca-
sia, Tartary nor Egypt could furnish
bronze to ancient Europe. In narrowing
the circle we would be led, as many
scientists have been, to look upon Asia
Minor as the country through which
bronze was carried, and India as the
place of its origin. But India itself is
large; from Cape Comorin to the Hima-
layas the distance is about that from
Marseilles to Petersburg. Moreover,
India does not produce its own bronze, it
imports it. This method, however,
which is not very scientific, and which
has led many men astray, merits some
consideration; bronze, which is a compo-
sition difficult to produce, must have
originated in a country where the ele-
ments are to be found; India does not
produce tin. We should regard the
peninsula of Malacca and Banca, which
are even to-day the two great centers
for the production of this metal, as the
birth-place of bronze; these facts then
are the result of the system of elimina-
tion. We do not mean to say one would
be led into error, but at most would
only propound a probable hypothesis.
The learned scientists have attempted to
solve the problem by reference to texts;
unfortunately the most ancient texts are
of recent date, considering epochs of
such antiquity. Moreover the authors of
these texts, whose individuality is a mat-
ter of doubt, were not well informed,
since none of them had any idea of the
three successive ages of humanity. In
vain did M. de Rougemont, in 1863, with
only the aid of texts, pretefld to have
solved in his cabinet the problem, for a
solution of which scientists have sounded
lakes, turned over the sods of the field,
and dug into the mountains. This
learned man, for whom the book of
Genesis was a sufficient authority in
metallurgy, designates Phoenicia as the
country from whence European bronze
was obtained.- But there are not mines
either of tin or copper in Phoenicia;
the nearest copper was to be had in the
isle of Cyprus which after all was not
Phoenician; besides, these were never
producers, but only merchants. It would
be impossible to show any Phoenician
bronze anterior to iron. We will here
add that the emblematical figures of
Europe are foreign to Phoenicia, and
that the author of the fourth chapter of
Genesis had but vague notions regarding
the origin of metals. There is then no
other method to follow but the observa-
tion and comparison of facts. If the
facts just enumerated prove the foreign
and unique origin of bronze industry, .
the local differences are liable to three
divisions in Europe; the Ural, Danubian
and Mediterranean, and these may be
subdivided into provinces. In noting
the successive epochs indicated by the
superposition of the layers of the pala-
fittes and stations, we can determine the
relative state of this industry in the dif-
ferent provinces of each group with
each of the three epochs of the bronze
age. The nature of the objects associated
in the layers show the successive phases
through which this industry passed.
Now the first bronzes sold in exchange
for amber, furs, leather and other prod-
ucts, to the polishers of stone, were
bijoux and amulets. We are able, by
comparison, to follow the march of the
commerce of jewelry from country to
country in each province. We next find
utensils and arms, and, lastly, appears
the era of metal beating, that is, the
hammering of bronze, following the
simple fusion, and thereby undergoing
a complete change.
These three series of observations,
founded on the thousand objects in the
public and private libraries, have shown
that if the Ural group which borders on
Asia is set aside, the provinces of the
Danubian group received bronze from *
regions near or below the Danube,
while Savoy, France and a part of Switz-
erland received theirs from Italy across
the Alps. The waters of the Danube
spread as far as the lakes of Eastern
Switzerland, and it is to this river we are
indebted for the bronze objects found in
the palafittes of Zurich, while those of
Savoy were borne by Italian waters.
The bronze works of Germany, Den-
mark and Sweden, and, to a certain ex-
tent, those of England and Ireland be-
long to the Danubian Industry.
The Italian industry fills the basin of
518
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the Rhone, and extended on one side as
far as Savoy, on the other to Cevennes,
then proceeded to the North of France,
its influence being felt as far as Great
Britain.
Now how was this propagation of
metallurgy effected? The foundries and
treasures answer the question, imperfect-
ly however. The earliest disclose foreign
workmen who established their workshop
in open fields, not in populated cities,
but in their vicinity. Not having any
permanent homes, they- wandered from
place to place and would here and there
melt old articles and mould new ones,
any deficiencies being supplied from
ingots or bars of bronze they carried
about with them; their treasures much
resembling the parcels and bundles of
nomadic merchants. How can we account
for the appearance of those found at the
top of mountains where there are no
habitations ? But the findings indicate
that these unfortunate men did not re-
turn and that they were a prey to
violence or misery in other quarters.
And why have these very foundries
preserved the molds and crucibles, the
ingots and broken objects which were to
be recast ? Why should these workmen
have left these articles behind them ?
Or, rather, have they not been the
victims of hatred or cupidity? Herodo-
tus says, that there was in his time a
sort of corporation or class composed of
nomadic founders who came from Asia.
During the whole of the middle ages,
these strangers differing from the men of
the West, frequented our cities and
towns. Their nomadic mode of life,
their unknown tongue, their strange
customs and religion which seemed to
be paganism, were the cause of their
being hated and ridiculed, although their
services were much needed. They were
murdered without mercy. Modern in-
dustry has almost banished them from
the most civilized countries; but they
overrun the East, the Middle and North
of Europe, without counting the whole
of Asia; they come like the men of the
bronze foundries, to remain a few days
in the fields near the cities. They are
known by different names in different
countries; tsiganes in Hungary, zingari
in Italy, bohemians in France, gyphtes or
Egyptians in Greece, gypsies in England,
and gitanas in Spain. They are not
united together, but are members of a
corporation dependant upon a chief. It
is from this chief residing at Pesth that
they receive the metal, and he himself
receives it from another who lives at
Temesvar, but whence does he obtain it?
It is probable that the similarity of the
events of the bronze age and the customs
of modern pewterers, will enable the
scientists to discover the course of
ancient metallurgy. The route of com-
merce is not much changed in countries
where the inventions of our day have
not yet penetrated. The processes were
perpetuated; in the East the same tribes
furnished men in the same business.
Now it is a fact that the tsiganes be-
long to India; we know from another
source that there were no castes in the
time of Veda, but there were then trades
among which that of founder had im-
portant place. But are these founders of
Aryan race ? Did they belong to that part
of the conquering nation which, in its
march to the Southest had not yet reach-
ed the valley of the Ganges, nor gone
beyond the Saraswati ? It is easily seen
that problems arise and multiply, and
how necessary it now is to pursue, out-
side of Pesth (the last place of the an-
thropological congress), the searching
which has been going on in the West
for the last quarter of a century.
The point of departure from the Italian
current is not any better known. Dis-
coveries have shown that the Rhodanian
industry comes from Italy, and that Italy
made more progress than the countries
farther North; but the working of bronze
is not any more original in Italy than it
is in France or Savoy. From which side
did the founders gain access to Italy?
Did they come from Greece or from the
islands ? And when it will have been
shown that they came from Greece and
that Greece preceded Italy in civilization
during the bronze epoch, it will be neces-
sary to show from whence Greece re-
ceived her bronze. Did she obtain it
from Asia Minor, Cyprus or Egypt, or
from some other country ? From the
moment we disregard the Adriatic, the
problem is unsolved, as the countries be-
yond this sea have not yet been searched.
The discoveries made at Santorin by M.
Fouque and the French school, and
especially the great researches of Dr.
Schliemann, at Troy, and Mycenae, throw
THE CO-EFFICIENT OF FRICTION ON RAILWAY BRAKES.
519
a ray of light on our subject, but do
not yet entirely solve our problem. And
this will not be until new discoveries
shall be made in many places in the
Grecian peninsula, in the islands, and
over the far-spreading surface of Asia.
In these countries there will needs be
found the commercial equivalent given
by the men of the West in exchange for
bronze brought by the Eastern men.
These objects of barter will be found to
consist principally of yellow amber,
a precious substance which remains in-
tact in the earth as well as in the sepul-
chres. The comparative study of religion
will furnish to science a helping hand,
for we know that the symbolical figures
of certain bronzes found in the west be-
long to the Aryan race and come from
Central Asia or India, such are the
swastika, the cross, the wheel, the cres-
cent, the disc, the stars and numbers.
These symbols, plainly characterized,
will be like so many stakes in all places
where they shall be found, and these
stakes marked on the chart of the world,
will indicate the metallurgic paths.
Philology already gives us a little in-
formation, but perhaps we should not
depend on it too much, for the names
given to the metals by the Aryans of
the West do not always have the same
signification they do in the East; but, as
in India for instance, the names desig-
nating the same metal, same industrial
product, same figure are always numer-
ous and significative, they will enable us
by comparisons, which will complete or
clear up those derived from science, and
thus will the study of texts, which has
been so abused, become useful. Be it as
it may, scientists admit at present that
the courses of metallurgy in Europe — that
of the Danube and that of Italy and the
Rhone start from the European conti-
nent and teud to converge towards a
central point of Asia which has not, how-
ever, yet been determined, but they also
admit that the epoch when bronze was
introduced in Europe among the people
of the neolithic period is yet at the state
of the geological period, and cannot be
included in any chronology. Will a
real date ever be determined upon, or at
least an approximate one ? We doubt it,
but at least hope so.
THE CO-EFFICIENT OF FRICTION FROM EXPERIMENTS ON
RAILWAY BRAKES.*
By Captain DOUGLAS GALTON, C.B„ F.R.S., D.C.L.
From "Journal of the Society of Arts."
The author of this paper has been
recently engaged in making some experi-
ments upon the co-efficient ' of friction
when the surfaces in contact move at
high velocities, in connection with the
action of brakes in use on railways; and
the results which have been arrived at
appear to present some interesting fea
tures in respect of the laws which govern
the co-efficient of friction.
These experiments form the first
installment of a series which it is intend-
ed to make, to ascertain, 1st, the actual
pressure which it is necessary to exert
on the wheels of a train to produce a
maximum retardation at different veloci-
ties; 2nd, the actual pressure exerted on
*Read before Section G of the British Association.
Dublin meeting.
the wheels in the several forms of con-
tinuous brakes now in use; 3rd, the time
required to bring the brake-blocks into
operation in different parts of a train in
the several forms of continuous brakes;
4th, the retarding power of the different
kinds of continuous brakes nov/ in use
on trains under similar conditions of
equal weight and running at the same
speed.
This paper includes the first series of
experiments only.
The author was enabled to make this
series through the courtesy of the Lon-
don, Brighton, and South Coast Railway
Company, and of their locomotive super-
intendent, Mr. Stroudley, who provided
a van and other facilities for making the
experiments; and through the courtesy
520
VAN NOSTRAND'S ENGINEERING MAGAZINE.
and assistance of Mr. Westinghouse, by
whom the recording apparatus was
designed. The author was assisted in
making the experiments, and in their
reduction, by Mr. Horace Darwin.
The experiments were made on the
Brighton Railway, with a special van
constructed for the purpose ; it was
attached to an engine, and was run at
various speeds, during which time
various forces were measured by self-
recording dynamometers. These dyna-
mometers were designed by Mr. West-
inghouse ; Their principle is that the
force to be measured acts on a piston
fitting in a cylinder full of water, and
the pressure of the water is measured by
a Richards' indicator, connected by a
pipe to the cylinder; thus, as the drum
revolves, diagrams are obtained, giving
the force acting on the piston. The
•advantages of this method are obvious,
as the indicator can be placed at any
convenient point, and the inertia of the
water tends to make the pencil keep a
position corresponding to the mean
force.
The piston, and what answers to the
cylinder, would be better described as a
ring fastened to the edge of a cylindrical
box. The rod by which the thrust is to
be measured is transmitted to the piston.
This piston merely consists of a cast-iron
disc, with a cavil y in its center, in which
the rounded end of the rod rests, and a
projecting piece at its center on the
other side acts as a guide. The ring,
which takes the place of the cylinder, is
of the same thickness as the piston, and
in its center the piston fits. This ring is
screwed to the edge of a cylindrical box,
to which the ring with the piston thus
forms a cover. The piston fits so as to
slide easily, with but little friction, and
is made water-tight by placing a disc of
india-rubber under it, which is fastened
to the center of the piston by a brass
collar, and has its edges clamped in
between the ring and the edge of the
cylindrical box. Thus we have a perfect-
ly water-tight piston, which will move
with very little friction, and as its move-
ment is very small, the disturbing effect
of the india-rubber at its edge may be
neglected; thus the indicator will regis-
ter the forces acting on the piston by
means of the pressure of the water. The
pipe leading to the indicator is screwed
into the socket. We will neglect the
valve for the present, and explain its use
a little further on. Suppose the whole
apparatus to be filled with water, and
that a force were applied to the piston
by the rod, it would force some of the
water out of the vessel through the
opening into the indicator cylinder; the
area of the indicator piston is half a
square inch, and its maximum range .8
of an inch, therefore the quantity of
water required to make a maximum
movement of the pencil is 0.4 cubic
inches, and as the area of the piston is
30 square inches, its movement would
only be 0.013, or -f-% inch, which is such
a small movement that the india-rubber
will introduce no appreciable error.
Now, if the indicator piston did not
leak, and if it were possible to keep
exactly the right quantity of water in
the apparatus, nothing more would be
required to make it work properly, but
as this is evidently impossible, the supply
valve becomes necessary. A small pipe,
leading from an accumulator loaded to a
greater pressure than can ever arise in
the vessel, is screwed into the socket;
the excess of pressure on the outer side
tends to close the valve ; there is also a
spring which forces the valve on to its
seat. This valve is seated with india-
rubber, and is made perfectly water-
tight. The spindle passes up so as very
nearly to touch the brass collar on the
underside of the piston. Suppose the
whole apparatus to be filled with water
when there is no force acting on the
piston ; then if a force is applied, this
will move the piston downwards, so as
to send some water into the indicator,,
and raise the pencil, and will also open
the valve, and, as the pressure in the
accumulator is in excess of that in the
vessel, the water will enter, and go on
entering till the piston is raised and no
longer opens the valve. Now, if the
force on the piston be removed, the indi-
cator spring will force a quantity of
water less than 0.4 cubic inches back
into the vessel and raise the piston less
than -^ inch, and thus the piston can
only move ^ inch above the position in
which it touched the valve. Again, if
we suppose a, smaller force to be applied
to the piston, it will not be pressed down
so far, and will not open the valve un-
less sufficient leakage has meantime
THE CO-EFFICIENT OF FRICTION ON RAILWAY BRAKES.
521
taken place to allow the piston to come
down through its full distance; thus the
valve always keeps the right quantity of
water in the apparatus to make it work
properly, by occasionally opening and
letting in enough water to make up for
leakage.
A special brake van was built by the
London, Brighton, and South Coast
Railway Company for these experi-
ments, to which the Westinghouse
automatic brake was applied, with four
dynamometers, like the one described,
attached to it. Nos. 1 and 2 measured
the retarding force which the friction of
the brake-blocks exert on the wheels;
No. 3, the force with which the blocks
press against the wheels; No. 4, the
force required to drag the van. The
arrangement of the levers for applying
the brake is not the same as that used
on the ordinary rolling stock of the
Brighton Railway, but has been slightly
modified by Mr. Westinghouse in order
to make the pressure equal on both sides
of the wheels, and to provide for the
application of the dynamometers. Into
the cylinder belonging to the Westing-
house brake apparatus the compressed
air flows from the reservoir when the
brake is applied, and forces the two
pistons apart, thus moving the two rods
outwards, and by means of their levers,
pressing the brake-blocks against the
wheels. It is evident that the pressure
must be equal on each side of the wheels,
and that the pressure on the dynamo-
meter No. 3 must be equal to the thrust
on the rod, and hence proportional jto
the pressure on the wheels. The lever
pivoted at its center will evidently tend
to turn with a moment equal to the
retarding moment exerted by the friction
of the brake-blocks on the wheels; and
hence the dynamometers Nos. 1 and 2
will register forces proportional to this
moment. The brake could be applied to
all the wheels of the van, but during the
experiments it was only applied to the
pair of wheels to the levers of which the
dynamometers were attached. Dyna-
mometer No. i is connected to a draw
bar by a lever, and thus registers the
force required to draw the van.
A self-recording speed indicator was
used, designed by Mr. Westinghouse.
This instrument has been repeatedly
tested, and was used at the brake trials
on the North British Railway, and on
the German State Railway. It consists
of a small dynamometer made on the
same principle as that just described; it
measures the centrifugal force of two
weights, which are made to revolve by a
strap from a pulley on a shaft driven by
friction gear from the pair of wheels to
which the brake was applied; a Richards5
indicator being used, as in the other dyn-
amometers. Thus, as the centrifugal
force varies as the square of the velocity,
the speed is got by taking the square
root of the ordinates at any point.
There is also a Bourdon gauge attached
to the above small dynamometer, with
the face divided in such a way that the
hand shows the speed in miles per hour.
These diagrams thus show the speed
of the pair of wheels to which the brake
was applied, and therefore the velocity
of the train at the moment of applying
the brake and subsequently — provided
there is no slipping. Any variation in
the speed diagram is due to the wheels
slipping, and shows to what extent and
in what way the brake stops the wheel.
Two of Mr. Stroudley's indicators
were fixed side by side in the van; one
attached to the axle belonging to the
braked wheels; the other to the axle
which was running free. The difference
of these indicators showed if slipping
took place.
Speed indicators were also attached to
the van; but these do not register auto-
matically.
The distribution of the weight of the
van between the two pairs of wheels was
obtained, as well as the weight of the
wheels and axles themselves.
In order to ascertain the weight
thrown on the braked wheels during the
progress of the experiment, a dynamom-
eter fitted to the springs of the van
showed the weight at every moment
carried on the unbraked wheels, from
which information it was easy to deduce
the weight on the braked wheels.
The indicators are all placed on a
table in the center of the van, and the
drums are made to revolve by the cords
being wound up on pulleys on the shaft.
This shaft is turned at a uniform rate by
a water-clock. This clock merely con-
sists of a plunger sliding in a cylinder
through a water-tight packing, and' load-
ed with a heavy weight; it is wound up.
522
VAN NOSTEAND'S ENGINEERING MAGAZINE.
by connecting it with the accumulator,
and at the beginning of each experiment
a small cock is opened, which allows the
water to run out and the weight to fall,
which thus turns the indicator down,
and at an ascertained uniform speed.
Thus the ordinates of the diagrams
taken from these indicators show the
various forces, and the abscissae the dis-
tance moved through by the van.
In these experiments the tyres were
of steel, and the brake-blocks of
cast iron.
The apparatus was designed by Mr.
Westinghouse, and constructed under
his supervision by the Brighton Railway
Co., through whose assistance these ex-
periments were carried into effect.
The effect of applying the brake to
the wheels is two-fold. So long as the
wheels to which brakes are applied con-
tinue to revolve at the rate of rotation
due to the forward movement of the
train, the effect of the blocks is to create
retardation by the friction between the
block and the wheel; but when the pres-
sure applied to the block causes the
friction to exceed the adhesion between
the wheels and rail, the rotation of the
wheels is arrested, and the wheel be-
comes fixed and slides on the rail, being
held in its fixed position by the brake-
blocks. "
Therefore the experiments give the
co-efficient of friction: —
1. Between the brake-blocks and the
wheel, which is equal to
the tangential force
the pressure applied.
2. Between the wheel and the rail,
which is the
friction of the brake-blocks
weight upon the wheels.
They moreover afford a measure of the
adhesion between the wheel and the rail.
It has been generally stated that there
is^ no difference in the co-efficient of
friction observed in the case of bodies at
rest, i.e., in a condition of static friction,
and the co-efficient of friction in the case
of moving bodies, i.e., in a condition of
kinetic friction; but Mr. Fleeming Jen-
kin, in his paper read before the Royal
Society, in April, 1377, upon the friction
between surfaces moving at very low
speeds, alludes to the fact that in cases
where a difference in the coefficient of
friction is observed between static and
kinetic friction, the static friction ex-
ceeds the kinetic.
Coulomb also points out his experi-
ments that in the case of static friction
the co-efficient of friction increased -with
the time during which the bodies had
been at rest.
The experiments of Coulomb, Rennie,
Morin, and Jenkin, were made with
bodies moving at comparatively low
velocities.
The table (p. 523) shows the mean
results obtained from a large number of
the experiments made with the apparatus
above described, upon the action between
the cast-iron brake-blocks and the wheels
fitted with steel tyres.
A limited number of experiments were
made with wrought iron blocks upon the
steel tyre, a mean of which gave the fol-
lowing result: —
Average.
48
31
18
o
<d
xji
ao
cd
fa
Co-efficient of Friction between
Wrought Iron blocks on Wheels.
2 K
I +=> cd
j < B
QC
110
,129
.170
o
o
CD
8 °
2 ®
4hCC
so .
2 a
o
T-H
<1
<
.11
.099
»o .
o c
The following table shows the result
obtained by the sliding of the wheel on
the rail, that is, a steel tyre and steel rails:
Co-efficient of Friction between
Average.
Wheel on
Kail, Steel on
Steel.
d
o
X5
a
o
cb '£ •
o <D o
d ©v£
O
<D
m.
o
CD
m
w
t-t
<v
CO
CD
o
CD
cjQ
t*
CD
g^M to
CO
lOrd
Bo
-rH CO
~ o
JO
©* cc
© d
3
CD
CD
fa
:3 ® 3
■4J
<
<
50
.04
45
.051
38
.57
.044
.044
25
.080
.074
15
.087
10
.110
THE CO-EFFICIENT OF FRICTION OE
RAILWAY
BRAKES.
' 523
Average.
Co-efficient of Friction between Cast-Iron Brake Blocks and
Steel Tyres of Wheels.
Feet per
Second.
At Commencement of
At from 5 to 7
At 12 to 16
At 24 to 25
Miles per Hour.
experiment, e. g.,
to Three Seconds.
Seconds.
Seconds.
Seconds.
60
55
50
88
.062
.054
.048
.043
73
.100
.070
.056
45
65
.125
40
58
.134
.100
.080
30
43
.184
.111
.098
20
29
.205
.175'
.128
.070
10
14
.320
.209
Under 5
7
.360
Fleeming Jenkin, Steel (
on steel dry (
.0002
.351 mean
to. 0086
.365 max.
Mofin, Iron on iron
.44
Rennie, At pressure of f
1.6 cwt. per square]
.275
inch wrought iron 1
* *
on cast iron [_
" — Steel on cast-iron.
.400
The general results of these tables
show that the co-efficient of friction
between moving surfaces varies inverse-
ly in a ratio dependent upon the velocity
at which the surfaces are moving past
each other; probably the equation would
be of the form of .
b + v
The co-efficient of friction, moreover,
at these velocities becomes smaller also
after the bodies have been in contact for
a short time. That is to say, the longer
the time the surfaces are in contact, the
smaller apparently does the eo-efficient
of friction become. This result appears
more marked in the case of cast-iron
blocks than of the wheel sliding on the
rail, at all events for the first thirty
seconds of the contact, the arrangement
not admitting of the experiments being
carried on for a longer time. This effect,
however, does not appear to be unnatur-
al, as the friction develops heat, and the
consequent expansion tends to close up
the pores, and to make the heated sur-
face a more united surface than the
colder surface. Besides which, it is
probable that in the act of rubbing,
small patches may be detached, which
may act as rollers between the surfaces.
It will also be observed that the co-
efficient of friction between the cast-iron
block and the steel tyre is much larger
than that between the steel tyre of the
wheel and the rails, which are also gen-
erally of steel.
As has been above mentioned, the
I sliding of the wheel on the rail takes
i place when the friction of the brake-
| blocks is greater than the adhesion be-
i tween the wheel and the rail, which is
l due to the weight upon the wheel. This
| was found to amount generally to about
24 to 28 per cent, of the weight.
The influence which these results have
| upon brakes for railway trains may be
! briefly summarized as follows: —
1. The application of brakes to the
! wheels, when skidding is not produced,
| does not appear to retard the rapidity of
rotation of the wheels.
2. When the rotation of the wheels
| falls below that due to the speed at
| which the train is moving, skidding
| appears to follow immediately.
3. The resistance which results from
j the application of brakes without skid-
| ding is greater than that caused by
skidded wheels.
4. The pressure required to skid the
| wheels is much higher than that required
to hold them skidded; and appears to
bear a relation to the weight on the
wheels themselves, as well as to their
adhesion and velocity.
j In order to produce a given result at
i different velocities, the pressure applied
| to the brake-blocks must vary in the
j proportion shown by the co-efficient of
friction.
Thus at 50 miles an hour the pressure
I required to make one pair of wheels
524
VAN NOSTRAND'S ENGINEERING MAGAZINE.
slide on the rail was nearly 27,000 lbs.,
whilst at 20 miles an hour a pressure of
about 10,300 lbs. was found sufficient to
obtain the same result.
The strain on the draw-bar showed
that the retarding force or the tangential
strain between the brake-blocks and the
wheels followed very nearly the same
law of variation. This is to say, in order
to produce a degree of friction on the
wheel at 50 miles an hour which shall
exert a retarding force on the train equal
to that at 20 miles an hour, the pressure
applied to the brake-blocks at 50 miles
an hour must be nearly two and a half
times as great as that required at 20
miles an hour, and a still greater press-
ure is required for higher velocities.
Therefore, whilst a comparatively low
pressure would make the wheels slide at
low velocities, it was difficult to obtain
any sufficient pressure to make the wheel
slide at velocities over 60 miles an hour.
The figures given in the above tables
must at present be accepted as only pro-
visional, until an accurate mean has been
obtained from the diagrams, which are
not yet all worked out. But it may be
assumed as an axiom that for high
velocities a brake is of comparatively
small value unless it can bring to bear a
high pressure upon the surface of the
tyre almost instantaneously, and it
should be so constructed that the press-
ure can be reduced in proportion as the
speed of the train is reduced, so as to
avoid the sliding of the wheels on the
rails.
EXPERIMENTS ON THE HEIGHTS, &C, OF JETS FROM THE
HYDRANTS OF THE KINGSTON WATERWORKS, JAMAICA.
By FELIX TARGET, Assoc. Inst. C. E.
From Proceedings of the Institution of Civil Engineers.
Numerous experiments were made
with nozzles of various sizes and differ-
ent lengths of hose, attached to hydrants
on the street mains, which mains were
of varying diameter. The accompanyiny
table (see p. 525) gives the results of
some of the experiments, those cases
best suited for comparison having been
selected. The height of the jet was
measured from the outlet at the nozzle
to the upper part of the curved spray
described by the jet. The copper hand-
pipe, 4 feet in length, was always held
breast-high, with the nozzle 5 feet to 6
feet off the ground. The leathern hose
was of the kind ordinarily used in Lon-
don, 2^ inches in diameter and in lengths
of 40 feet. The hydrants and stamp
pipes were Bateman and Moore's. The
mains were nearly new, and were coated
inside with Dr. Angus Smith's prepara-
tion. The draught of water for the
town for twenty-four hours was equal
to 1,266,600 gallons, the maximum per
hour being 93,000 gallons. During the
time the experiments were carried on the
draught was 45,000 gallons per hour,
which is the average night consumption.
The experiments were made in the early
morning in a still atmosphere.
The accompanying figures show the
forms of three of the nozzles. Up to
the highest pressures the \% inch nozzle
threw a much more compact jet, with
less spray, than either the \$ inch or the
J-i inch nozzle, the smaller of which oc-
casioned the greatest spray. The heights
are only correct within a few inches, as
the jets slightly varied during the time
of the experiments, notwithstanding that
the pressure gauge, which was used to
ascertain the head of water, remained
nearly steady.
From these experiments it is difficult
to arrive at any correct law, or formula,
for calculating both the height and the
delivery of water from jets in a town.
It is evident, however, that with high
pressures, although the 2-inch mains are
large enough to furnish an ample and
constant supply to forty houses, each
drawing from 200 gallons to 500 gallons
per day, yet they are undoubtedly too
small for fire purposes without the aid of
a fire engine.
The four inch mains gave results
EXPERIMENTS ON THE HEIGHTS, ETC., OF JETS.
525
Results of Experiments on the Heights of Jets, delivery of Water,
etc., at the kingston waterworks, jamaica.
1
Number of experi-
ment.
2
Size of Noz-
zle in Inches.
3 4
Height of Jet! Number of
in Feet. IGal. p. Min.
i
5
Head in feet
at Hydrant.
6
Length of Main
in Yards .
No. 1. — With one (
length of hose. . . . (
14
T5
20* 92 53|
34* j 55
1,083 of 21-inch.
+ 50 of 4-inch.
Ditto, with three j
lengths of hose (
n
18
29*
«
No. 4. — With one
length of hose
H
38
44£
44"
122
73
92
1,585 of 21-inch.
+ 133 of 12-inch.
No. 5. — With one
length of hose. . . .
if
9
25
27
66
55
47
92
1,585 of 21-inch.
+ 183 of 12-inch.
-|- 66 of 2-inch.
No. 6. — With one
length of hose
Ditto, with three
lengths of hose. . . .
Ditto, with six
lengths of hose. . .
it
14
T6
11
55
68
77
138
94
73
122.4
1 1,585 of 21-inch.
1 + 600 of 12-inch,
j -f- 116 of 4-inch.
48-3-
62
66
If
26*
51*
62
100
82
No. 7. — With one
length of hose
17
T6
14
1C
11
7
24
27
52
47
122.4
1,585 of 21-inch.
+ 600 of 12-inch.
+ 166 of 4-inch.
+ 20 of 2-inch.
No. 9. — With one
length of hose
Ditto, with three j
lengths of hose ... 1
u
14
T5
11
T¥
Hi
32
32
12
29
32
60
47
106
1,585 of 21-inch.
+ 266 of 12-inch.
4- 60 of 4-inch.
4 100 of 2-inch.
No. 13.— With one(
length of hose 1
17
58
85
84
136
130
94
156
1,585 of 21-inch.
+ 1,266 of 12-in.
4- 116 of 4-inch.
Ditto, with three \
lengths of hose 1
17
if
16
48
64
62
180
132
94
Ditto, with five \
lengths of hose. ... 1
14
If
T6
41
55
62
143
132 •
103
No. 14.— With one!
length of hose |
TS
14
16
ii
T6
15*
28
35
73
73
60
154|
1,585 of 21-inch.
+ 1,266 of 12-in.
+ 70 of 4-inch.
4- 87 of 2-inch.
Ditto, with three J
lengths of hose 1
17
14
If
rg-
18*
29
46
78
68
66
Ditto, with five j
lengths of hose j
it
14
5
26
35*
70
66
55
No. 20.
Direct
main .
—No hose,
from 2-inch^
10*
22*
37
64
55
157
1,585 of 21-inch
+ 1,050 of 12-in.
4- 125 of 4-inch.
+ 111 of 2-inch.
526
VAN NO strand's engineering magazine.
Scale ^2 full size.
nearly equal to the 12 inch mains with j the -fj inch nozzle with the higher
an effective head of 155 feet. Taking j pressures appeared to give the best re-
height and quantity into consideration | suits.
THE PREVENTION OF RAILWAY AND STEAMSHIP
ACCIDENTS.*
Bt Pkofessor OSBORNE REYNOLDS.
From "Iron."
The past twelve months has been no
ordinary period. Political events of the
very first magnitude have followed each
other in rapid succession, and the
mechanical events have been of such
vast importance and interest that they
have successfully competed with their
political rivals, and have secured for
themselves no ordinary amount of public
interest.
Railway and steamship disasters of
this year are calculated to impress upon
us that, take what precautions we may,
we cannot do away with accidents alto-
gether. We must face the risk, and all
we can hope to do is to reduce this risk
to a minimum. It is to questions con-
cerning this minimum risk that I wish to
direct your attention.
The attention paid to the means of
* An address before the Scientific and Mechanical
Society of Manchester, England.
preventing accidents and mitigating the
consequences has been steadily growing,
and during the last few years it has been
considerable; and this not only by en-
gineers and those more directly con-
cerned with the accidents, but also by
the public and the Legislature. The aid
of Parliament has been claimed in al-
most every direction, and numerous im-
portant statutes have been passed with a
view to diminish risk. The object of
this attention has not been solely the
means of locomotion, but has embraced
every species of mechanical appliance in
the use of which there is risk to human
life; and it is only for the purpose of re-
ducing my subject within reasonable
limits that I shall confine myself to con-
sidering some of the risks attendant
upon locomotion. That rapid locomo-
tion can never be altogether rendered
free from risk will, I think, be generally
RAILWAY AND STEAMSHIP ACCIDENTS.
527
admitted. It is the conclusion which
must be drawn from the experience we
meet with in the exercise of our natural
powers. For all animals, when in their
natural state, do meet with accidents in
consequence of their movements. And
adopting the now generally accepted hy-
pothesis as to the survival of the fittest,
we at once see that the limit which ex-
ists to the size and speed of animals is
only maintained in virtue of the increase
of the accidents consequent on any over-
stepping of these limits.
From the fact that man has already
gone beyond nature in the size and speed
of his locomotive structures, it may be
thought that when design comes in, the
laws found to hold in natural selection
no longer apply. Further consideration,
however, will show that this is by no
means the case. It is true that in our
railway trains — to take the most striking
instance — we have far exceeded the size
and considerably exceeded the speed of
any walking or running animal. But,
think for one moment ! How have we
done this? Simply by modifying the
conditions under which the movement is
accomplished. All animals, as far. as
nature has selected them, have been se-
lected to exercise their powers under the
conditions at the surface of the earth as
these conditions exist; whereas our loco-
motive engines are possible only after
the conditions have been completely
modified by the construction of railways.
Even our carriages and teams of horses
would be altogether useless were it not
for the existence of good roads. Thus
we see that it is not as a constructor of
locomotive machines that man has won
the race, but by laboriously modifying
the conditions which these machines
have to meet.
Thus, in considering the liability to ac-
cident in the means of locomotion con-
structed by man, as compares with the
liability to accidents met by animals in
the exercise of their natural powers, it
must be remembered that failure in the
due maintenance of the two conditions —
the improved road and the rule of the
road — may be important elements in the
former.
As far as ships are concerned, the last
is the only condition. Here there is no
improvement in the road, and no arti-
ficial guides, such as in the railway in-
sist, to a certain extent, on the mainten-
ance of the rule of the road. *
In virtue of the smoothness of the
railway we can pass the natural limits as-
regards size and speed of locomotive
structures, and in virtue of the rule of
the road we do away to some extent
with the necessity for such comparative-
ly great powers of stopping and turning
as those possessed by swift annimals;
but we cannot do away altogether with
the necessity for such powers, and in
spite of all possible improvement in the
conditions under which locomotion takes
place, it would appear that the minimum
of these powers consistent with safety
remains fixed by the surrounding condi-
tions. For there are certain conditions
which play an essential, although it may
be thought a secondary, part in our
means of locomotion, which conditions,
it may appear, that we have no power to
modify to any great extent. These relate
to the distances at which we can see and
hear. Although by the use of telescopes
we may increase the optical power of our
eyes to almost any extent, it is found
that such an increase is of no use to us
in guiding ourselves or our structures
amongst obstacles on the earth's surface;
the limits to the distance at which we
can see such obstacles being fixed by the
form of the earth's surface and the con-
dition of the atmosphere, rather than by
the power of our eyes. These conditions
vary greatly. In some places, and at
some times3 a signal may be visible for
miles, while at other times it may not be
visible many yards. When the condi-
tions of the atmosphere are such that
they limit this distance, no increase in
the power of our eyes would make any
difference; and their power is amply
sufficient when the distance is not other-
wise limited.
The effect of these conditions is much
more important as regards safe naviga-
tion at sea than as regards the driving of
our trains. Dwelling for one moment on
ships, we see at once how this limit to
the distance at which we can depend on
our eyes and ears to warn us of danger,
must place a limit on the size and speed
of our vessels. Large and swift vessels
will only have the same room in which
to manoeuvre out of danger as small
ones. Hence, in order that they may as
successfully accomplish such manoeuvres,
528
VAN NOSTRAND'S ENGINEERING MAGAZINE.
the large #and swift vessels should have
proportionately much greater powers of
stopping, starting and turning than small
vessels. Up to the present time, how-
ever, no means have been found of rend-
ering the manoeuvring of la^ge ships
proportionately greater than the man-
oeuvring power of small ships.
To railway trains the same law does
not apply with the same force; still, it
does apply. We have not made our
system of distance signalling so complete
but that there do continually arise cases
in which the first warning the engine-
driver receives of an obstruction ahead
is from phe obstruction itself; and under
these circumstances the chance of safety
lies in the power of stopping the train
within the limited distance. In such
cases the power of stopping with a heavy
fast train, in order to give the same
chance of safety, must be proportionately
greater than with a slower and lighter
train.
It is certain that we have not as yet
developed to the utmost the brake power
on our trains, or the steering and stop-
ping powers of our ships; but it is cer-
tain that there is a limit to these powers,
and the only question is, how far are we
from this limit ? This brings me to what
is, to me, the most pleasant part of my
subject, namely, the consideration of
certain progressive steps that have re-
cently been made, which, although they
have not attracted much notice, are nev-
ertheless extremely important to our
means of locomotion, and are also im-
portant as showing that however far
happy guess-work may carry us towards
perfection, perfection itself is rarely, if
ever, to be attained except by scientific
method.
Up to within the last few years our
attention has been so closely occupied in
developing and perfecting the primary
power in our means of locomotion, that
but little notice has been paid to such
secondary considerations as the powers
of stopping, starting, or turning, as the
case may be; for these such appliances
as came at once to hand were at first
deemed sufficient; thus hand brakes on
those parts of the train where they could
be at once applied, and the rudder and
hand wheel, such as may be said to have
grown on the sterns of ships, were ac-
cepted without question. And it was
only when we had so far perfected our
locomotive structures as regards what
may be called their locomotive functions
that they have outrun our means of hold-
ing them; and when the alterations in
the conditions consequent on the increase
of traffic (of which I shall have more to
say presently) have increased the neces-
sity for greater powers of avoiding each
other, we find ourselves driven to con-
sider how far the power of stopping and
turning may be improved.
As regards railway trains the question
has been very widely taken up. The
great prize held out to the inventor of
the best continuous brake brought many
able competitors into the field, while the
urgency of the case has led to the adop-
tion of much more direct means of test-
ing the merits of the various inventions
than ever fell to the good fortune of
other inventors.
The result appears likely to be very in-
structive, apart from the direct object in-
volved. It appears likely to afford an
illustration of the fact that it is no use
attempting the solution of such a prob-
lem except by the thorough and scientific
method.
The stopping power arising from a
single brake was known to depend on
the tightness with which the brake
blocks were screwed against the wheels
up to a certain point; and it was appar-
ently obvious that the tighter the better
until the wheels no longer revolved —
until, in fact, the wheels were skidded —
to produce the greatest effect; therefore,
it was thought that all the guard or
driver had to do was to skid his wheels.
Hence, when an emergency arose, the
brakes were invariably screwed home
and the wheels skidded. This practice,
which has prevailed without question
for forty years, is an instance of how far
general experience can be depended on
to remove a misconception. It is now-
found for the first time that by skidding
the wheels the brake loses nearly half its
greatest power of stopping the train.
If the brake is applied with the greatest
force short of skidding the wheels, the
train will stop in something like half the
distance required if the wheels are skid-
ded. •
How many lives have been sacrificed
to this misconception it is not pleasant
to think. Thanks to Captain Galton, it
RAILWAY AND STEAMSHIP ACCIDENTS.
529
is now removed, and it now only remains
to choose the best means of applying the
brakes so as to produce the greatest
effect. Captain Galton has shown us
the greatest stopping power we can
obtain from one pair of wheels, and
when we have succeeded in obtaining
this from every pair of wheels on a train
we shall have reached the minimum limit
of our stopping power. But this is
something like four times greater than
the stopping power of ordinary trains.
Turning now to the manoeuvring pow-
ers of steamships, I come to the subject
which has engaged no small part of my
attention for several years. The man-
oeuvring powers of ships involve not
only their power of stopping, but also
their means of turning, and as regards
improvement, the question of turning is
the more important, for, as regards
powers of stopping, a sailing ship has
none other than that of turning her head
into the wind; while with steam ships
their greatest stopping power is devel-
oped by the reversal of their engines;
and as they are all provided with the
power to reverse, the only question is as
to the rapidity with which it can be
accomplished; and in this respect there
is not great room for improvement. So
far it has been the almost universal cus-
tom to reverse the engines by hand, and
in the case of large engines the operation
might occupy as much as thirty seconds,
which would be time lost. Recently,
however, steam reversing gear has come
into vogue for large vessels, and by
means of this the engines can be reversed
by a mere turn of the wrist. We cannot,
therefore, hope to increase the powers
which vessels have of stopping them-
selves. As regards a vessel's power of
turning, however, it is different. Taking
screw-steamships as being the most im-
portant class of ships, and those to
which, owing to their great speed,
manoeuvring powers are most important,
we may see from the very great number
of collisions in which screw-steamers
take a part that, as at present sent to
sea, the turning powers of these vessels
are altogether insufficient. We all saw
an authoritative statement that there
had been upwards of seventy collisions
in the Thames alone within twelve
months, and that in by far the greater
part of these collisions a screw-steamship
Vol. XIX.— No. 6—34
was involved. The insufficiency of the
turning powers of screw Jsteamers has
long been acknowledged by all those
who have to do with them; but, strange
to say, until within the last few years,
no systematic attempts had been made
to remedy the evil. It has been with
the steering of screw steamers just as it
was with the stopping of railway trains;
the rudder and hand wheel, like the
brakes on the engine and tender, came
ready to hand when steamers were first
introduced. And hitherto gross miscon-
ception has prevailed. It may be that
the fact of the rudder and wheel having
held its own for so long on sailing ships
led to the conviction that it was already
proved to afford the best means of steer-
ing, and as the rudder of the steamer
was itself similar to that of the sailing
vessel, and was similarly placed — name-
ly, at the stern — it was assumed that it
must produce the same effect. Such
views would gather strength from the
fact that in paddle steamships the rud-
der was found to answer its purpose as
well as in the sailing ships. At any
rate, for some twenty years no attempts
were made to investigate the action of
the rudder in screw-steamers, although
from the time of the first screw-steamer
going to sea anomalies in the steering
presented themselves.
The action of a rudder at first sight
appears to be so simple and obvious that
it seems as if nobody thought of looking
closer into the question. The rudder
appears to act the simple part of a guide
to the stern of the ship. When straight
the rudder allows the ship to go straight
on, but when it is turned it then guides
the stern of the ship out of the direction
in which the head is moving, and so
causes the ship to turn. This is the
apparent action of the rudder, and this
would be its action if the ship did not
offer any resistance to be turned. Owing
to this resistance, however, and to the
yielding nature of the water, the rudder
does not act the part of a rigid guide to
the stern of the ship, but only exerts
what may be called a tendency to guide
the stern. This, also, is to a certain
extent obvious. And it is also obvious
that by increasing the size of the rudder
the tendency which it exerts to guide
the stern will be increased. But what is
not obvious, and what was not seen until
530
VAN NOSTRAND'S ENGINEERING MAGAZINE.
recent years is, that the tendency which
the rudder exerts is not due solely to the
forces which act between the water and
the rudder, but to the increased pressure
of the water which the rudder causes
against that side of the ship towards
which it is turned. The importance of
this fact being entirely overlooked, it
was not seen that the opening of a large
space, such as the screw-way immediate-
ly in front of the rudder must in itself
greatly diminish the tendency of the
rudder to guide the ship. And further,
such was the confidence in what may be
called the obvious action of the rudder,
that when it was found, as it was im-
mediately on the introduction of screws,
that, no matter how fast a vessel might
be going through the water, if the screw
was stopped or reversed the action of
the rudder was not only feeble but
uncertain, it was not supposed that this
effect was due to any change in the
teadency which the rudder exerted to
turn the ship, but that it was due to the
tendency which the screw exerted to
counteract the effect of the rudder.
This blind confidence in the consistent
action of the rudder, whatever may
appear to the contrary, is so strong even
at the present day, that, although from
his own experience when manoeuvring
his ship in rivers and in port, every j
captain and pilot knows that his rudder
is all but useless to him whenever his |
screw is stopped or reversed, , and his
vessel still be moving forward slowly,
numerous pilots and captains adhere to
the opinion that such would not be the
case if the vessel were moving fast, for
then, they argue, that the action of the
rudder would be sufficient to counteract
the action of the screw; and so great is
their confidence in this view that they
never try the experiment but wait until
a collision is imminent, and then when,
perhaps, as in the case of the Konig
Wilhelm and the Kurfurst, the ship,
with her screw reversed, pursues her
own unguided way right into the sides
of another, they refuse to give up their
confidence in their rudder, and maintain,
in spite of all evidence to the contrary,
that their orders could not have been
obeyed. The whole error arises from a
failure to grasp the circumstances on
which the action of the rudder depends.
As long, and only as long as the water is
rushing backwards past the rudder, will
the rudder exert its normal tendency to
guide the ship.
This is no mere theory. For, at the
instance of a committee of the British
Association, experiments to test these
conclusions have been made on twelve
steamers ranging from 4000 tons down-
wards; and in every case it is found
that, no matter how fast the ship may
be going, the instant the screw is re-
versed the action of the rudder is also
reversed, and rendered comparatively
feeble. It is therefore now conclusively
shown that it was a misconception to
suppose that the rudder would exert its
usual influence with its screw stopped or
reversed. And there can be no doubt
that but for this misconception, many
collisions might ha*ve been prevented.
The result of these experiments has
been to bring to light what the manoeuv-
ring power of screw-steamers really is,
and hence to clear the way to making
the best possible use of that power.
Inefficient as a rudder on a screw-
steamer must always be under certain
circumstances, with large vessels its
inefficiency is greatly increased by the
insufficient means provided for turning it
in case of emergency.
This evil might at once be remedied.
Nothing is easier than to apply some
power in place of the hand-wheel.
Various contrivances for doing this
have already been devised; and there is
no doubt that the inventor of the best
steering apparatus will secure a prize
nearly, if not quite equal to that which
will fall to the inventor of the best
brake. The experience just mentioned
as regards brakes may, however, be
taken as a caution by those whose
interest it is to find the 'best steering
apparatus. Just as the question of the
best brake is now found to lie beyond
the mere means of applying it, so the
best steering apparatus may be found to
involve more than the mere means of
turning the rudder.
It may be that the whole power of the
engines of a ship will be brought to bear
in bringing her round. Indeed, this has
been already done in the instance of
twin screws; and certain recent inven-
tions are said to apply this power at still
greater advantage. As regards the
turning power of ships, therefore, it is
KAILWAY AND STEAMSHIP ACCIDENTS.
531
clear that although there doubtless is a
limit, yet, owing primarily to ignorance
as to what the turning powers of our
screw-steamers really are, and also to
the insufficient power now applied to
turn the rudders, we are far from having
reached the limit; and we may fairly
hope that the risk at present attending
the navigation of screw-steamers will,
inasmuch as it depends on the want of
turning power, be considerably reduced.
That we shall eventually develop to
the utmost the powers of stopping and
turning, whether on railways or on ships,
and make use of all our scientific knowl-
edge to discover those methods, may,
I think, well be argued from the pro-
gress of ' late years. Although time has
not allowed me to enter upon them in
this address, there are many other cir-
cumstances under our control which
affect the risk of locomotion beside the
adequacy of the powers of manoeuvring.
And it is very satisfactory to notice that
as regards one of these circumstances,
and the one to which, until recently,
accidents were mainly to be attributed,
we appear, at all events, as judging
from the accidents of this year, to have
reached perfection. This is the ade-
quacy of the strength of our structures.
It is but rarely now that we hear of a
railway axle, a rail, a beam, or even a
boiler, breaking under its legitimate
load. This certainly has only been
reached by the most elaborate research,
aided by scientific knowledge, and by
the institution of most careful systems of
tests and periodic inspection. But these
have all been done, and we may fairly
hope that what has been accomplished in
one direction will be followed in others
until we shall have substituted through-
out every department of the manufacture
and working of our structures a thorough-
ly understood art for what was a few
years ago merely a field for ingenuity.
But it must not be imagined that all
the future improvements there may be in
the stopping power of our trains or in
the turning.power of our steamboats, or
in whatever may affect their safety, will
all be allowed to go to diminish the risk.
As the risk with structures at their
present sizes and moving at their present
speeds is diminished, it will probably be
as it has been — the sizes and speed will
be increased, and more than this. I
have already mentioned the increased
risk consequent on the increased traffic
of our railways and the increased crowd-
ing of our seas. This crowding goes to
form one of the conditions under which
locomotion has to be accomplished; and
it is most -important to notice that this
crowding can itself only be limited by
the increased risk which it causes.
Inasmuch as the risk of locomotion
depends upon crowding so far, any
diminution to risk which may be ac-
complished by increasing the manoeuv-
ring powers of our locomotive structures
seems likely to be followed by increased
traffic and crowding, and thus the ad-
vantage derived on the one hand may be
balanced by the disadvantage on the
other.
It thus appears that after all precau-
tions risk is a necessity of locomotion,
and that the speed and size of our
structures as well as the extent of the
possible traffic are limited by the risk.
And it may well be asked, what, then, is
the limit to the risk? This is a question
of morality. The limit to the risk is the
extent of risk to which we are willing to
run. To accomplish some object or even
to save ourselves trouble we are all of us
willing to run some risk. Let our system
of working be ever so perfect, the im-
munity from accidents will result in
neglect, and this must culminate in
accidents. The. loss of the Eurydice
appears to have been a marked instance
of this, as does also the Sittingbourne
accident, and it does not appear impossi-
ble that this may also have to be said of
the loss of the Princess Alice.
Notwithstanding all this, statistics
show us that the risks are and have been
steadily diminishing. Nor is this dimin-
ution of risk other than we should
expect. As novices we put up with that
which experience teaches us to with-
stand, and hence, as we become more
familiar with the incidents of traveling,
we come to object to risks of travelers
and responsibilities of officials which we
know may be reduced.
It is proposed to hold an international
industrial exhibition in Glasgow in 1880,
the matter being in the hands of a num-
ber of influential citizens headed by the
Lord Provost.
532
VAN NOSTRAND'S ENGINEERING MAGAZINE.
THE RECTANGLES THAT MAY BE INSCRIBED IN A GIVEN
RECTANGLE.
By Professor W. ALLAN.
Written for Van Nostrand's Engineering Magazine.
Having seen several allusions to this
problem of late I am induced to send
you the following discussion of it. The
problem has a useful application in the
construction of Howe trusses and of
similar structures.
I. To determine generally the rect-
angles that may be inscribed in a given
rectangle, ABCD.
Assume some point as H, on the
shorter side of the given rectangle, as
one of the vertices of an inscribed rect-
angle. Let its distance from A be = x.
Then through this point describe a circle
with its center at O, the center of ABCD.
The points in which this circle cuts the
sides of ABCD are the points of the
vertices of the inscribed rectangles that
are possible when our first assumed point
is one of these vertices. Each of the
eight points gotten may serve as one of
the vertices of two rectangles (like those
having a common vertex at F). The two
rectangles that may be drawn at each
set of two points will evidently in every
case be like those at F. No other rect-
angle, save those in the figure, can be
inscribed with a vertex at F.
These rectangles have some pretty re-
lations.
Let «=AB = shorter, and 5=AC =
longer side of given rectangle. Let AF
=y, AK=x. Then FC=b-y and HB
= a— £c=AP. From the similar triangles
AFP and FCK, we have
AP : FC; ; AF : CK=AH .-. a-x : b-y
\\y : a
whence
y*—x*—by-{-ax=o (1)
and the value of x in terms of y is
±
vu
y*-by
Let s and p be the sides of the inscribed
rectangles. Referring to the smaller of
two inscribed in Fig. 1 we see that it, to-
gether with four triangles, make up the
area of the given rectangle which is equal
to ab. The triangles are the two equal
ones AFH and GLD, and the other two
equal ones FCL and GHB. The area of
the first two = xy, and of the second
two =(a— x) (b—y). The area of the
rectangle FG—sp. Hence
(a—x) (b—y)+xy + sp=ab
(a-y)|f±/£+y._ty
+ v\l±\/C^ + y*-by\+sp=ab
ab x /^
.*• ^yT^-ylf j+j/*-Jy (2>
The two values of the area sp correspond
to the two rectangles with vertices at F.
The sura of these two rectangles is seen
to be always =ab= area of the given
rectangle. /As the point H is carried
towards A, the smaller rectangle dimin-
ishes, and the other increases until at the
limit one becomes the diagonal AD, and
the other becomes the given rectangle
itself. As H is assumed nearer and
nearer to M (the middle point of AC) the
two inscribed rectangles approach each
other in size, and when H coincides with
M, they become equal, and each is— one
half the circumscribed rectangle, ABCD.
II. To determine the sides of the
KECTANGLES INSCRIBED IN A 'GIVEN RECTANGLE.
533
'blocks on which diagonals of a Howe
truss abut, so that the faces may be
perpendicular to the diagonals.
The face, or hypothenuse of the block
(FH, Fig. 1) is equal to the breadth of
the brace, and is the dimension given.
The relation between this and one of the
sides of the block leads, as Prof. Woods
remarks in his book, to an equation of
the fourth degree, which is insoluble.
But the relation between the two sides
of the block is given by equation (l)
y* — x2 — by -f ax = o
This is the equation of an Equilateral
Hyperbola, which is shown in Fig. 2.
Fig.2.
Transposing the origin to O the center
of^ABCD, eq. (1) becomes
y>-x> = -i(a*-b<)
(3)
this A and B. With A as center and
radius equal to the given breadth of the
base describe a circle. At the point
where this circle intersects the Hyper-
bola within the rectangle, draw the co-
ordinates of the Hyperbola referred to
A as origin. They are the sides of the
block whose face equals the radius of the
intersecting circle.
The form of the Hyperbola changes
only with the values of a and b. A table
may be readily constructed giving the
values of the sides of the blocks for
given faces when the values of a and b
are fixed. The values of these sides may
be obtained by measuring the co-ordi-
nates on a carefully prepared drawing,
or by measuring one co-ordinate, and
then calculating the others by means of
eq. (1). A specimen of such a table is
appended, when b
is taken=20 and
a=10:
Face.
X
y
Face.
X
y
0.20
0.18
0.089
2.20
2.03
0.845
0.40
0.37
0180
! 2.40
2.22
0.904
0.60
0.55
0.264
i 2.60
2.41
0.961
0.80
0.73
0.345
! 2.80
2.60
1.014
1.00
0.91
0.423
3.00
2.80
1.065
1.20
1.10
0.503
! 3.20
3.00
1.112
1.40
1.28
0.575
! 3.40
3.20
1.155
1.60
1.46
0.645
3.60
3.40
1.194
1.80
1.64
0.711
I 3.80
3.60
1.228
2.00
1.83
0.778
4.00
3.80
1.258
And O is the center of the Hyperbola.
The vertex is V, and the curve passes
In the contribution of Prof. Haupt,
published in the November number of
our Magazine, the statement was made
that the new survey of the Delaware
River then in progress was "under the
supervision of Capt. S. C. McCorkle."
It is desired to explain that Mr. McCorkle
was the assistant in charge of the local
triangulation. " The topography of that
portion of the river shores then being
surveyed was under the direction of As-
sistant R. M. Bache, and the hydro-
graphy of the river was executed by
Assistant H. L. Marindin, under the
special supervision of Assistant Henry
Mitchell."
The entire work was organized and
directed by Hon. C. P. Patterson, Super-
intendent of theU. S. Coast and Geodetic
Surveys.
534
VAN NOSTRAND'S ENGINEERING MAGAZINE.
ON A NEW METHOD OF DETECTING OVERSTRAIN IN IRON
AND OTHER METALS, AND ON ITS APPLICATION IN THE
INVESTIGATION OF THE CAUSES OF ACCIDENTS TO
BRIDGES AND OTHER CONSTRUCTIONS.
By ROBERT H. THURSTON, C. E.
A Paper read before the American Society of Civil Engineers.
It has been shown by the writer* and
by other investigators that, when a metal
is subjected to stress exceeding that re-
quired to strain it beyond its original
apparent, or "primitive," elastic limit,
this primitive elastic limit becomes
elevated, and that strain- diagrams obtain-
ed autographically, or by carefully plot-
ting the results of well conducted tests
of such metal, are " the loci of the suc-
cessive limits of elasticity of the metal
at the successive positions of set."f
It has been shown by the writer also
that at the successive positions of set,
strain being intermitted, a new elastic
limit is, on renewing the application of
the distorting force, found to exist at a
point which approximately measures the
magnitude of the load at the moment of
intermission. J;
It has been still further shown by the
writer, and by Commander Beardslee,
U.S.N., by direct experiment in the
Mechanical Laboratory of the Stevens
Institute of Technology, and at the
Washington Navy Yard, tnat the normal
elastic limit, as exhibited on strain dia-
grams of tests conducted without inter-
mission of stress, is exalted or depressed
when intermission of distortion occurs,
according as the metal belongs to the
iron or to the tin class.§ This elevation
of the normal elastic limit by intermit-
ting strain i->, as has been shown, vari-
ble in amount with different materials of
the iron class and the rate at which this
exaltation progresses is also variable.
With the same material and under the
same conditions of manufacture and of
subsequent treatment, the rate of exalt-
ation is quite definite and may be ex-
pressed by a very simple formula. The
* See Trans. Am. Soc. C. E., 1874, et. seq., Journal
Franklin Institute, 1873; Van Xostrand's Eclectic Engi-
neering Magazine, 1873, etc., etc.
t On the strength, etc., of Materials of Construction,
1874, Sec, 20.
t On the Mechanical Treatment of Metals ; Metallurgi-
cal Review, 1877 ; Engineering and Mining Journal. 1877.
§ Trans. Am. Soc. C. E., 1.877.
writer has experimented with bridge ma-
terial, and Commander Beardslee has
examined metal specially adapted for use
in chain cables, for which latter purpose
an iron is required, as in bridge building,
to be tough as well as strong and uni-
form in structure and composition. The
experiments of the latter investigator
have extended to a wider range than
have those of the writer, and the effect
of the intermission of strains considera-
bly exceeding the primitive elastic limit
has been determined by him for periods
of from one minute to one year.* From
a study of the results of such researches
and from a comparison with the latter
investigation, which was found to be
confirmatory of the deduction, the writer
has found that, with such iron as is here
described, the process of exaltation of
the normal elastic limit due to any given
degree of strain usually nearly reaches a
maximum in the course of a few days of
rest after strain, its progress being rapid
at first and the rate of increase quickly
diminishing with time. For good bridge
irons, the amount of the excess of the
exalted limit, as shown by subsequent
test, above the stress at which the load
had been previously removed may be ex-
pressed approximately by the formula :
Ex — h Log. T+ 1.50 per cent.;
in which the time, T, is given in hours
of rest after removal of the tensile stress
which produced the noted stretch.
Thus, in the figure, which is a facsimile
of a part of a strain-diagram produced
by such an iron, during a test in which
the intermission of stress was of too
brief duration to cause an observable
exaltation of the normal elastic limit in
a diagram drawn on so small a scale,
the point E is the primitive elastic limit
* The result on this investigation is completed and
will be presented to the President of the United States
by the United States Board appointed to test iron*
steel, etc.
OVERSTRAIN IN IRON AND OTHER METALS.
535
iiisisass:
Hiiir
111
of the material, and El JE11 JEU1 E1Y,
are the normal elastic limits correspond-
ing to sets under loads which have
strained it beyond that primitive elastic
limit. In the example here illustrated,
the primitive limit is found at* about
20,000 pounds per square inch, or 1,400
kilograms per square centimeter, and the
other points are those corresponding to
loads of, respectively, 21,000, 22,500,
25,000 and 30,000 pounds on the inch, or
to 1,470, 1,575, 1,750 and 2,100 kilo-
grams on the square centimeter. The
corresponding extensions, as shown on
the diagram, are 1.25, 2.53, 4.50 and 6.78
per cent.
Had the stress been intermitted at
either of these points any considerable
period of time, there would have been
observed a rise in the diagram as above
stated like that shown in Fig. 1, at EY
the normal elastic limit e, being on sub-
sequent test, found altered and a new
limit, e, observed. The extent of this
elevation of the limit would be the
greater as the time of rest was greater,
as already seen.
Thus, it is seen that a metal, once
overstrained, carries, permanently, un-
mistakable evidence of the fact * and
can be made to reveal the amount of
such overstrain at any later time with a
fair degree of accuracy. This evidence
cannot be entirely destroyed, even by
a moderate degree of annealing. Often,
only annealing from a high heat, or
reheating and reworking, can remove it
absolutely Thus, too, a structure, brok-
en down by causes producing overstrain
in its tension members, or in its trans-
* The writer has found by subsequent tests, that
transverse strain produces the same effect upon the
elastic limit for tension.
versely loaded beams (and, probably, in
compression members — although the
writer is not yet fully assured of the
latter), retains in every piece a register
of the maximum load to which that
piece has ever been subjected; and the
strain -sheet of the structure, as strained
at the instant of breaking down, can be
thus laid down with a fair degree of
certainty.
Here, then, when the work above
detailed shall have been properly com-
plemented with experimental determina-
tions of the behavior of all the materials
of general use in construction, may be
found a means of tracing the overstrains
which have resulted in the destruction or
the injury of any iron or steel structure,
and of ascertaining the cause and the
method of its failure, in cases frequently
happening in which they are indetermin-
able by any of the usual methods of
investigation.
The fact of the normal variation of the
elastic limit, as change of form progress-
es under gradually increased load, has
been well established by the experiments
of Hodgkinson, Clark, Mallett, and other
English investigators; by Tresca, partic-
ularly, in France; by Werder and Baus-
chinger in Germany, and by Beardslee,
the writer and others in the United
States.
The exaltation of the series of normal
limits so produced, still further, as shown
by the writer and as seen in Fig. 1, by
the intermission of strain, as at EY, is
also a matter of no uncertainty as to its
character, although much more study is
needed to determine the modifying
effects of time of intermission on metals
of the two great classes and of differing
composition. The method above outlined
536
VAN NOSTRANTrS ENGINEERING MAGAZINE.
of determining the extent of previous
overstrain may therefore be expected to
have many useful applications.
In illustration of an application of the
facts thus reviewed to the determination
of the causes and the method of the in-
jury or the destruction of a structure,
assume the existence of a set of con-
ditions which is familiar to, probably,
every engineer in the country who has
seen much of the Howe truss, and of
some other forms of bridges, as frequent-
ly built before the present generation of
professional bridge builders effected a
revolution in that department of engi-
neering construction.
Suppose one of these bridges to have
been built with a span of 150 feet and to
have been given such proportions that,
with a weight of 1,200 pounds per run-
ning foot and a load of one ton per run-
ning foot, the maximum stress on end-
rods, or other members most strained, is
as high as 20,000 pounds per square inch
of section of metal. Suppose this bridge
to have its tension members composed
of a fair, but unrefined, iron, having an
elastic limit at about 17,000 pounds per
inch, and a tenacity of 45,000 to 48,000
pounds, and with an extensibility of
about 20 per cent.
Suppose this structure to break down
under a load exceeding that usually sus-
tained in ordinary work, and the cause
of the disaster to be " involved in mys-
tery."
Suppose portions of the several ten-
sion members to be subsequently re-
moved, and, a few days after the acci-
dent, to be carefully tested with the fol-
lowing results :
Elastic Limit.
Tenacity.
Sample No. 1.... 16, 500
46,000
" 2.... 18,000
48,000
" 3.... 30,000
48,000
" 4.... 22,500
50,000
" 5.... 25,000
52,000
" 6.... 27,500
52,000
" 7.... 28,000
52,000
" 8.... 30,000
52,000
" 9.... 32,000
53,000
" 10.... 34,000
53,000
And that the extensibility is found to
be as little as from ten to fifteen per
cent.
Suppose it to be found that the tension
members were straight bolts without up-
set ends, the threads being cut, as was
once common, in such a manner that the
section at the bottom of the thread is
one-third less than the sectional area of
the body of the bar. Suppose, finally,
that the location of the tested pieces in
the structure being noted, it is found
that the stronger metal, having also the
highest elastic limit, came from the
neighborhood of the point at which the
bridge gave way, and that the weakest
metal and that exhibiting the lowest
elastic limit came usually from points
more or less remote from the break. It
is not likely that in all cases the increase
in the altitude of the elastic limit and
the increase noted in the ultimate
strength of the samples would exhibit
a regular order coincident with the order
of the rods as to position in the struc-
ture; since the magnitude and the ar-
rangement of the bars would, to a certain
extent, determine the relative amounts
of strain thrown upon them by overload-
ing any one part of the truss. For pres-
ent purposes we may assume the order
of arrangement to be thus coincident.
On examination of the figures as above
given, the engineer would conclude :
First, that the original apparent elastic
limit of the iron used in this case must
have been not far from 17,000 pounds
per square inch, and that its tenacity was
between 46,000 and 48,000 pounds; sec-
ondly, that this primitive elastic limit
had been elevated, by subsequent loads
exceeding that 'amount, to the higher
figures given by the bars numbered from
3 to 10 inclusive; thirdly, that the ulti-
mate strength of the material had been,
in some examples given above, increased
by similarly intermitted strain.
It would be concluded that the ordi-
nary loads, such as had been carried pre-
viously to the entrance upon the bridge
of that which caused its destruction,
never exceeded, in their straining action,
16,500 pounds per square inch of section
of tension rod at the part of the truss
from which No. 1 had been taken, and
that the other rods tested had carried,
probably at the time of the accident,
loads approximately equal to those re-
quired to strain them to the extent
measured by their elastic limits at the
time of testing them.
It would be concluded that the rod
from which No. 1 0 was cut was either
that most strained by the load, and there-
fore nearest the point of fracture of the
OVERSTRAIN IN IRON AND OTHER METALS.
537
truss, or that it was very near that point,
and it would be made the basis of com-
parison in further studying the case.
As this elastic limit approaches most
nearly the breaking strength of the
metal, we may apply the formula for the
elevation of the elastic limit with time
after intermitted strain which has been
above given as derived from tests of a
metal of very similar quality. Taking
the time of intermission as one week,
the extent of the increase has a probable
value not far from E' — 5 log. 168 + 1.5
=nearly 12^ per cent. The magnitude
of the stress upon this piece at the time
of the accident was therefore 34,000 less
one-ninth of that value, or about 30,000
pounds per square inch of cross-section
of the bar. This corresponds to about
45,000 pounds per square inch at the
bottom of the thread, and is within five
per cent, of the primitive breaking
strength of the iron. The bar, if broken
at the screwed portion, has therefore
yielded either under a dead load which
was at least equal to its maximum resist-
ance, or under a smaller load acting so
suddenly as to have the effect of a real
4i live load." Or the slight difference
here noted may be due to a flaw at the
point of fracture. However that may
be, it is almost certain that the body of
the rod has sustained a stress of not far
from 30,000 pounds per square inch.
But it is found, on further investiga-
tion, that the load on the structure at
the time of the accident was but suffi-
cient to make the maximum stress on
these rods — if properly distributed —
20,000 pounds per square inch at the
threaded part of the piece; which piece,
it has been seen, has been broken by a
strain nearly double that figure. The
fact is at once inferable that the load
came upon these members with such
suddenness as to have at least the effect
of a live load (as taken in the text-books)
and giving a maximum stress equal to
twice that produced by the same load
gradually applied, i.e., the case in which
the load falls, through a height equal to
the extension of the piece strained by it,
the resistances being assumed to increase
directly as the extension up to the point
of rupture, — an assumption which is
approximately correct for brittle materi-
als like hard cast iron, but quite errone-
ous in the case of some ductile materials,
which latter sometimes give a " work of
ultimate resistance," amounting to three-
fourths or even five-sixths of the product
of maximum resistance by the extension.
This accident was therefore caused by
the entrance upon the bridge of a load
capable of straining the metal to about
one-half of its ultimate strength, if slowly
applied, but which, in consequence of
its sudden application, doubled that
stress..
This sudden action may have been a
consequence either of its coming upon
the structure at a very high speed, or a
result of the loosening of a nut, or of the
breaking of a part of either the bridge
floor or of one of the trucks of the train.
The latter occurrence, permiting the load
to fall even a very small distance, would
be sufficient.
This paper is not presented as a per-
fectly satisfactory statement of definite
facts from which absolutely reliable con-
clusions can be drawn. The whole sub-
ject is deserving, however, of very care-
ful and very extended experimental in-
vestigation, and the writer has been able
to obtain but a small amount of satis-
factory definite information in regard to
it as yet. The figures given do not ex-
| actly represent those obtained from any
I actual case. They do, however, fairly
| illustrate the limited experience of the
writer, and are nearly exact for at least
one case; they may serve to indicate the
possible value of the cautious application
of the method here outlined of studying
the causes of such accidents as are con-
sidered in the hypothetical case here
taken.
The same method may sometimes be
used to ascertain the probable cause of a
boiler explosion by determining whether
the metal has been subjected to over-
strain in consequence of overpressure.
The causes of accidents to machinery
may also be thus detected, and many
other applications will suggest themselves
to every engineer.
Bituminous coal has been discovered
near Aurora, in Nevada. It is but a few
feet below the surface, and the seam is
said to be about 7 ft. in thickness. If
this turns out to be true, it will, in con-
nection with the metalliferous discoveries
in Nevada, be of the greatest importance.
538
VAN nostrand's engineering magazine.
A NEW GRAPHICAL CONSTRUCTION FOR DETERMINING
THE MAXIMUM STRESSES IN THE WEB OF A BRIDGE TRUSS .
By WARD BALDWIN, University of Cincinnati.
Written for Van Nostrand's Magazine.
In Volume XVIII of this Magazine,
page 26, Professor Eddy has given a
graphical construction for finding the
maximum stresses in a bridge truss. The
determination of the maximum shearing
stresses, in the article referred to, con-
sists in successively subtracting the dif-
ference between the maximum shearing
stresses on two consecutive joints from
the total reaction of the pier when the
live load covers the entire bridge. As
thus constructed the errors are cumula-
tive.
It is the object of this paper to propose
a construction which will determine each
of the maximum shearing stresses in a
truss independently, and not as the sum
or ^ difference of several magnitudes.
This, it is believed, permits of greater
accuracy, than any construction hereto-
fore proposed.
Suppose the bridge to be a through
bridge. Let the live load consist of one
or more locomotives which, to begin with,
stand at n" of the joints x1 aj2, etc., at
the left hand end of the truss, together
with a uniform train of cars which
covers the remaining joints.
Let s^ s2, etc., be the maximum shear-
ing stresses at the joints jc,, aja, etc.
w=the dead load on one joint.
w'=ihe load, due to the train of cars,
on one joint.
(w' + w") =the load, due to the engines^
on one joint.
w= the number of the joint considered,
reckoning from A.
n'=zihe number of panels in the truss.
?i"=ihe number of joints loaded with
locomotives.
m=n'— nfl .
Now in the figure lay off ex^—r, the
reaction at the pier A when the live load
covers the entire bridge in the manner
above stated. The value of Exx-=r can
be readily found by the principle of the
lever. When the train moves off to the
right, so that no live load rests on the
joint £Cj and the locomotives stand on the
n" joints x„ sc3, &c, then the reaction of
the pier A has been diminished by the
nf \
amount j-(w' + w"). and it has been
increased by the amount —t -, w" \
as was proven in the article before re-
ferred to. Therefore the reaction of
the pier A has been diminished by the
difference of these quantities, that is to
say, by the amount — \in' —X)wf -\- n" w"\
Now the maximum shear at the joint sc2
is this reaction diminished by the load at
the joint xJt Therefore the maximum
shear at the joint x2 is
s2—r—w 7 \{n' — \)w' -\- n';w'f]
By similar reasoning the maximum shearl-
ing stress at the joint x% is found to be
&=<
— w r\{n' — 2)w' + n"w"\
n
Successive maximum shears may be com-
puted in a similar manner, and in general
the shear at the joint xn is^
= r-
n '
MAXIMUM STRESSES IN THE WEB OF A BRIDGE TRUSS.
539
-^[(n'-fyo' + n'w"]- . ..
-w — \[{ri-(n-1)]w' + n"v>"\
76
provided n is less than nf — (nn — 1) =
m + 1, as will be shown presently; and
sn has a maximum value provided
n'
Now if for convenience we let q=
[w + — } (n'—\)w' + n"w") ], then the
values of the maximum shearing stresses
may be expressed as follows :
s=r
s.=r-q.
$ =zr—q—q+ =r—\2q , I.
w' 2w' / 3w'\
and in general it is evident that
(/ x 1 + 2 + 3 + .. . + (w— 2)
sn =r- j (n-1) q ^^ ^— ± 1
*j=r-j(»-lfo ^
Now in the figure lay oft.BC=(n' — \)q
and join ca^ by the line *„ £,, etc. At xs,
x4, etc., lay off x3 fz=—„ *< f<=^7
xJf>—'—, •> etc., and in general, z« /n =
(n—l)(n — 2) , m
^t v> . Then the ordinates /2
^5/3 ^3) /I *4» etc., represent the amounts
to be subtracted from r to obtain the
maximum shearing stresses at the joints
x2, x3i x0 etc. For these ordinates are
3g ^r h etc.,
^-^n-\n{a)
equal to <?, -J 2q
i\- i
respectively; and these amounts must be
taken from r to obtain the maximum
shearing stresses at the joints xai x3, <e4,
etc., as is shown by formula (a). Lay
off these ordinates on ex^r, measuring
from e. Then the distances from xy to
the points thus found represent the
maximum shearing stresses at the joints
xi-> xzt etc.
From e and the points thus found
draw lines parallel to the inclined mem-
bers of the web, viz., al c„ a2 c3, etc.,
terminating in the horizontal through xx,.
Then these lines represent the maximum
stress on the members al clt a3 ca, etc.
From the points fvif2,fai etc., lay off
the vertical ordinates fle=r, f^e^ry
f% e3=r, etc. Then the ordinates tx eiy
ti ev h en etc., represent the maximum
shearing stresses at the joints xv a?2, xz.
etc. Then the point G shows where
the sign of the shear changes, and there-
fore how far counters are needed.
On BClaj off DC— in' — \)w and join
Bx1 by the line rlS ya, etc. Then the
ordinates rt el9 i\ e2, r3 e3, etc., represent
the reactions of the pier A as the train
moves towards the right and the live
load is removed from one joint after
another; for rx ^=0, r2 t2=w, r3 £3 = 2w,.
etc. . . . But 0, w, 2w, 3w>, etc., are the
amounts which must be taken from the
reactions of 1he pier A to obtain the
maximum shearing stresses at the joints
1) 2' 3? etc.
Now when the train has moved so far
to the right that the live load rests on
only n" joints, the live load consists of
engines alone; and, reckoning from Ay
the number of the first joint loaded with
the live load is {n'—n")—m. To find
the shearing stress at the next joint to
the right, that is at the joint xm+if the
live load is moved off of the joint xmy
and the reaction of the pier A is thu&
n"
diminished by the amount —rlw' + w")*
As the engine load on the joint next to
B is at the same time moved to the pier
B, the reaction of A is not affected by the
additional load on B. Therefore the shear-
ing stress at the joint xm+i is less than
the shearing stress at the joint xm by an
amount e'qual to «0+— (w; + w"). By
similar reasoning we can also at once
show that the shearing stress at the joint
JKm+2 is less than the shearing stress at
the joint xm+\ by an amount equal to
jo I
10 -\ 7— (w' + «/'), etc.
Now, for convenience, let the ordinate
n"
fmtm equal pr and also let 10 + — T (w' + w"}
equal h, then the shearing stresses at the
joints #m+], Xm+2, are evidently,
sm-i-l=r—(p + h)
sm-{-2=r- (p + [2A 7{w' + w")'])
sm+3=zr— (i? + [3A-— (w' + w")]), etc
540
VAN NOSTKAND7S ENGINEERING MAGAZINE.
which shearing stresses have evidently a
maximum value, provided the end of the
live load has not yet passed the center
of the bridge. This may be the case if
the span is short, or if the value of n" is
great. Finally, at the joint n\ the
shearing stress is
, , r „, l+2 + 3+....+ (rc"-l)
{w' + w")-\
(w + w)]);
=.r—{p\n"h-
n'\n"
2n'
and this is the reaction of the pier B due
to the dead load.
In the figure from the point (/"m draw a
line to E parallel to xxc. From E lay
off EH=n"h, and join fm to H. From
the points hlt A2, etc., lay off the ordinates
h1fm-\-2=-7(w, + w"), h2fm+2=-r
III IV
(wf + w"), etc.
Then will the ordinates fm-t-1, tm-\-l,
Jm+2, tm+2, etc., represent the amounts
to be taken from r to obtain the shearing
stresses at the joints xm-\-l, xm-\-2, etc.;
for these ordinates are equal to p + h,
p + lh r (w' + w"). etc. From the
n v
points /thus found lay off the distances
Jm-hl em-hl=r, fm-\-2 em-+-2 + r, etc.; then
tm-h-1 em-t-1, tm-\-2 em-+-2, etc., represent
the shearing stresses on the joints xm+1,
Xm-+-2, etc. ^
The ordinate en> tn> represents the
shear at B when the live load has passed
off of the bridge; therefore ent tn> is the
reaction of B due to the dead load. The
ordinate enirn> represents the reaction of
A when the live load has left the bridge,
as is shown above, and is, therefore, the
reaction at A due to the dead load.
Hence, evidently, en< should be equi-
distant from tnr and rn>.
If, instead of an unsymmetrically dis-
tributed live load, a uniform live load
covers the bridge and moves off to the
right, the construction used to determine
the shearing stresses after the live load
consisted entirely of engines is applicable
to the whole bridge, and p becomes zero.
If the bridge is a deck bridge instead
of a through bridge, the ordinates t1 e,
% e2i ^3 e3> etc«) represent the maximum
stresses on the ties cta2, c2a3, etc., instead
of on the ties c2a2, c3a3i etc. But the
maximum stresses on the inclined mem-
bers are the same in a deck as in a
through bridge, and therefore the num-
ber of counters is the same for both
forms of bridge.
The construction proposed may be
briefly stated as follows :
To determine the maximum shearing
stresses, lay off' BC= {nf — \) \w-\ ,
(n' — l) w/ + n"w")~\ = (n' — l)qi and draw
the line xxC; at the joints a?,,, cc3, etc.,
lay off distances equal to 0, — , — r etc;
then the ordinates between the points
thus found and the line xx C are to be
subtracted from x1e=r, to obtain the
maximum shearing stresses at the joints
Xtf ^3» XH e^C#
q may be found graphically by the
construction given by Professor Eddy,
as is shown in the figure, and the line
xx £2 be prolonged to c. Then B C will
equal {nf— 1)</. The quantities 0, — ,,
3io' 6w' . ^ , 7
— r, — , etc., are the terms of a regular
n' nf
series whose first differences are —r. w'y
n'
2 3
—r.w', —r.w\ etc., in regular numerical
n n
order, and they may therefore be calcu-
lated mentally and laid off at once.
Suppose, for example, that in the
figure the scale of lengths is 30 feet to
an inch, and the scale of weights is 40
tons to an inch. Then
6^=^=73.5 tons,
tu = Q tons,
to' = Q tons,
w"=3 tons,
^'=12, n" — Z and m=9.
Also BC=(n'-l)q-UX[Q+T\{QQ + 9)]
= 11 X 12.25 tons=134.75 tons,
*x/i=°> a. /,=<>, ^/3=0-5 ton, xj =
1.5 tons, xbfb=S tons, x6fe=5 tons.
And the maximum shears are, by meas-
urement,
3=73.5 tons, £3=61.25 tons, 3=49.5
tons, 3=38-25 tons, 3=27.5 tons.
The position of the point G shows that
only one counter is needed on each side
of the center. It is the practice to put
in one or two more counters on each side
of the center than is necessary for a
static load.
RIVER IMPROVEMENT WORKS.
541
ON THE EFFECT OF KLVER IMPROVEMENT WORKS.*
By JAMES DILLON, Mem. Inst. C.E.I.
From "Engineering."
The great floods, due to the unusual
rainfall of late years, have caused so
much damage and misery in different
countries that the subject is at present
engaging the serious attention of scien-
tific men.
It is known that in the great majority
of cases the discharging capacity of the
rivers and their tributaries is insufficient
to carry off the flood waters without
overflowing their banks, due in a measure
to the existence of numerous hard gravel
and rock shoals, mill-dams, badly con-
structed bridges, and insufficient sec-
tional areas, &c. To remove these de-
fects it has hitherto been the practice to
deal with a system of rivers, or at least
with the main and principal tributaries
belonging to one catchment basin (by
catchment basin is meant the entire dis-
trict of country unwatered by a river
and its tributaries, it may, therefore,
embrace mountains or lakes), and to
endeavor to borrow money from Govern-
ment or other parties to carry out the
works necessary for the removal of the
obstructions above referred to, com-
mencing upon the lower reaches of the
river system and carrying the works
upwards. Many useful works have been
carried out in different countries, partic-
ularly in Ireland, where the progress of
the arterial drainage works, under 5 and
6 Vict., c. 39, up to July 31, 1863, was
as follows : The total amount of loans
obtained and expended under the direction
•of Government, previous to 1863, on
river or arterial drainage works, equaled
£2,390,612 (exclusive of the coast of
Shannon), and the repayments in respect
thereof, including interest, amounted on
March 31, 1878, to £1,341,522. This
money was expended on various river
works extending over not less than 2000
miles of rivers and tributaries, the works
being designed so as to convey the flood
waters from 120 different catchment
basins of an aggregate area of 6,358,358
statute acres. The object of these works
was to relieve 266,736 statute acres of
_ — *
* Read before Section G of the British . Association :
Dublin meeting.
good land, at an average cost of £7 per
acre, adjoining the 2000 miles of river
banks and shores of lakes, from the inju-
rious effects of flood waters. Particular
attention should be paid to the fact that
the ground covered with water was only
4-J- per cent., or about -j^ of the entire
catchment basins, as this will have to be
dwelt upon hereafter. The above works
were executed by Drainage Commission-
ers appointed under 5 and 6 Vict., c. 89,.
and no doubt conferred great benefits on
the country, but both the country and
the Government concurred in thinking
the outlay was too great, and further action
as regards new works was suspended,
under the 5 and 6 Vict. Then, in 1863,.
owing to previous agitation in and out of
Parliament, the Government sanctioned
a general drainage act being passed for
Ireland authorizing private parties to
form drainage districts (see Act 26 and
27 Vict. c. 88, and Acts passed amend-
ing the same), provided that two-thirds
of the injured land in value are owned
by parties assenting to the project, and
if the two-thirds petition, the Govern-
ment will grant the necessary money to
to carry out the works, if satisfied with
the financial prospects of the undertak-
ing.
Progress of arterial drainage works in
Ireland, under 26 and 27 Vict., c. 88,
from 1863, to July 31, 1878, was as fol-
lows : Under this act the works for 37
districts have been sanctioned and are
now nearly completed. Their effect has
been to drain and free from floods not
less than 71,000 statute acres, at a cost of
! £389,000, equal to an average outlay of
! not less than £5 9s. per acre as compared
I with £7 per acre under the 5th and 6th
I Vict. Notwithstanding that the above
results as regards Ireland are so far sat-
isfactory, still it is a fact that year by
year such works are becoming more dif-
ficult of accomplishment, owing to the
impossibility of adjusting the conflicting
interests of the upland and lowland pro-
prietors. If the lowland proprietors pro-
mote a scheme for the improvement of
their larger and consequently more costly
542
VAN NOSTKAND7S ENGINEERING MAGAZINE.
sections of their rivers, they generally
try to tax the upland proprietors for
works that can confer no benefit upon
them, while if the upland proprietors try
to improve their smaller and less costly
rivers they are opposed by the lowland
proprietors, who contend that their floods
aVe made worse by the drainage of the
uplands, &c. The extent to which these
supposed conflicting interests interfere
with the carrying out of such works may
be judged from the fact that the Board
of Public Works in Ireland, in their
report for 1 87*7 -78, announce that from
Ireland last year there was only one
application for a new drainage district, so
that unless subsequent legislation proves
more successful, there will be few if any
useful works of this class carried out
when those already sanctioned are com-
pleted.
It has occurred to the author, who has
been entrusted with the expenditure of
some £157,000 on rivers, or nearly one-
half of the money expended on such
works since 1863, under 26 and 27 Vict.,
that the principal objection to the exten-
sion of such works can be proved to be
unfounded, viz., that the extension of
arterial drainage or river works up coun-
try increases the volume of river floods
sent down from the drained districts, to
the injury of the low-land proprietors.
The following are the particulars of
some arterial drainage works lately car-
ried out under the direction of the author,
which had not the effect of increasing
the flopd discharge. They are known as
the Upper Inny Drainage Works, and
were commenced in 1870. These works
extend over 82 miles of rivers and tribu-
taries, . the catchment basin or area of
country discharging its waters into this
system of rivers extends over an area of
273 square miles, and its centre is situa-
ted about 53 miles to the west of Dublin,
at a level of 211 feet above the sea, the
rock formation being limestone.
The whole of the river works were
designed so as to carry off the flood
waters about 4 feet below the surface of
land, which formerly saturated and cov-
ered with water 12,260 statute acres of
land, equal to 7 per cent, of the catch-
ment basin. During the progress of the
works it was necessary to carry out
extensive rock, gravel, and other excava-
tions, and to rebuild some 60 bridges,
the total cost of which will amount to
some £60,000. The works under the
author's charge were commenced near
Lough Iron, at the point where the
Lower Inny Works, carried out under
the care of the Drainage Commissioners
of Ireland, were suspended on account
of their excessive cost and want of funds,
&c, to proceed further up country. Pre-
vious to the commencement of the Upper
Inny Drainage Works, the average sum-
mer discharge in the river from the upper
district amounted to .0689 per acre per
minute, and the average flood discharge
to .4896 per acre per minute. After the
execution of the works the average sum-
mer discharge at the same place amounted
to .0827 per acre per minute, and the
flood discharge to .4827 per acre per
minute. Similar results have been ob-
tained by the author in other districts,
and it may be added that the Earl of
Ross and Mr. Forsyth, late engineer to
the Commissioners of Public Works of
Ireland, both concur in his views on the
subject.
It has been shown that in the above dis-
trict, while the total area of the catchment
basin amounted to 273 square miles or
175,000 acres, the ground covered with
water along the 82 miles of rivers and
tributaries amounted to only 12,250
acres, or about 7 per cent, of the whole
catchment basin, and, further, that the
average breadth of the flooded land
equaled 75 statute perches, or 1237 feet.
This is not an exceptional case, for it is
already stated in this paper that in the
other districts already executed, 120 in
number, the total amount of flood water
along the river flats covered only 4^ per
cent, of the catchment basin. From this
it follows that there is not less than 93 e
per cent, of the Upper Inny district sit-
uated above flood level, so that 93 per
cent, of the floods due to the rainfall
falling upon the entire district could flow
just as freely on to the 7 per cent,
flooded lands along the river banks be-
fore the execution of the works as they
could after the execution of said works.
It must not be forgotten that the
flooded 7 per cent, is always more or less
saturated with water, particularly in win-
ter, and that when so saturated it can
hold no additional water except the flood
water flowing over its surface.
It is believed by many that this flood
RIVER IMPROVEMENT WORKS.
543
water remains stationary, but this cannot
be, inasmuch as the river valley has
always (unless in very exceptional cases)
a very perceptible fall, otherwise suffi-
cient velocity would not have been given
to the waters of the country to have cut
any kind of river through its valley.
From this it follows that whether the
river banks are or are not flooded, the
whole of the flood waters in the river
valley are in motion until they rise to
what is known as the maximum flood
level. At this level the waters will only
remain so long, as the maximum yield
from the maximum rainfall in the dis-
trict can keep them up to it. So that as
long as the flood level remains stationary
no further ponding of the flood waters
can take place, and therefore the maxi-
mum flood due to the maximum rainfall
will flow along the river valley for days
and weeks without increasing in height,
spreading over the country where the
banks are low, and confining itself to the
river where there are cliffs or high banks,
but not exceeding the maximum flood
level even at these -points. If then the
flood waters do not increase in height
the whole flood discharge must be pass-
ing out of the district, and if this can
occur before a river is enlarged or im-
proved, enlarging a river channel can
neither increase the rainfall nor the flood
yield from same sent down to lowland
proprietors.
Having shown that the sheets of flood
waters spreading over a river valley are
in constant motion, it will be observed
that just as they commenced to rise be-
cause they could not get away before
the flood waters came pouring into the
river valley from the more distant por-
tions of the catchment basin, so after the
maximum floods have ceased to flow
from the last named places into the main
river valley these sheets of flood water
fall in level, and in doing so increase the
flood discharges towards the close of the
wet season by the volume of water cov-
ering the river valley which would not
have been there had the district been
drained. It will be said if the effect of
the arterial drainage works is to prevent
the accumulation of large sheets of flood
waters in a river valley, then the floods
must be increased by the passing away
of these waters.
The author believes this to be a mis-
take. He has already shown that the
flooded ground seldom averages 7 per
cent, of the catchment basins, and in the
Inny district above referred to it
equaled an average breadth of 1537
feet or 7 per cent. If then a number of
tributary rivers with catchment basins
some 2 miles in breadth, and some 8 or 10
miles in length, branch off at nearly right
angles to the main river, along "which
this 7 per cent, flooded land exists; then
if you divide these lateral catchment ba-
sins into 100 parts, allowing the 7 parts
near the river to be flooded, it will be
evident that the maximum flood due to
the maximum rainfall on the seven parts,
or 7 per cent, at the junction of the trib-
utaries with the main river, will have
passed away into the main river before
the maximum floods from the second,
third, or tenth miles, &c, could reach
the last named junctions, were the riv-
ers not dammed up with shoals, &c, so
that the time required to allow of the
river valleys being covered with water
before the execution of the works would,
if properly utilized, be more than suffi-
cient to allow of said water passing down
a properly constructed river channel be-
fore the maximum floods could reach the
main "river from the second, third, or
tenth mile back from the main river. If
this holds good in narrow tributary
catchment basins, so will it be applica-
ble to all forms of catchment basins, no
matter what their direction with regard
to the main channel. The author be-
lieves, then, that the effect of arterial
drainage works is to enable the floods
from the fractional 4, 7 or 8 per cent,
flooded lands near the main arteries to
pass off after execution of works many
hours or days sooner, according to the
magnitude and length of the rainfall and
district than before execution of works;
and that by securing a longer interval of
time for the discharge of a flood of given
magnitude, arterial drainage works can-
not increase the maximum flood dis-
charges of a district.
As this view of the case is confirmed
by the author's observations, he invites
discussion in order to test its accuracy.
When once it is established that the floods
in a river valley are not increased by the
enlargement or improvement of either
an upper or lower section of the river
passing through said valley, the author
544
VAN nostrand's engineering magazine.
believes that the public and the Govern-
ment would find it more practical to deal
with the improvement of rivers in the
following way :
Whenever any considerable portion of
a country is flooded by the overflow of a
river or its tributaries, and the parties
injuriously affected are desirous of ap-
plying to Government through the Com-
missioners of Public Works in England,
Ireland, or elsewhere, for a loan to im-
prove their land, they should be required
to furnish a section of the rivers to be
improved, taking care to extend the sec-
tions down the river until a sufficient out-
fall is obtained for the successful carry-
ing out of the proposed works. Should
the Board of Works report in favor of
the project, the treasury could advance
the necessary funds, thus enabling useful
works to be carried out under the super-
intendance of drainage boards acquainted
with the localities with which their inter-
ests are connected, instead of losing
many years in endeavoring to embrace
all the districts or tributary districts in
one large, costly and unmanageable
scheme. By this method the works
could be commenced in divisions corre-
sponding to the natural sub-outfalls of
the country, commencing at the fall near-
est to or furthest from the sea.
Should this method be sanctioned by
Government on any large scale, now that
it is proposed to grant loans for river
works, on a moiety of the proprietors
assenting to the project instead of re-
quiring two-thirds, as formerly, a great
impetus would be given to the extension
of such works, conferring great benefits
upon the country by increasing the value
of land, and giving at the same time ad-
ditional employment, and circulating
large sums of money among the work-
ing classes in the agricultural districts.
Although the facts thus briefly set forth
in this paper are now publicly brought
forward by the author for the first time,
still, in the case of the great Barrow
river scheme which embraces a country
of 625 square miles, he has succeeded in
overcoming hostile opposition (based
upon increased flooding) to its being ex-
ecuted in divisions instead of in one vast
unmanageable whole. Of this work two
divisions have already been sanctioned
by Parliament, and are now nearly com-
pleted.
The object of the author in bring-
ing forward these facts is that the prac-
ticability of dealing with large river
systems in divisions, instead of in one
whole, may become more universally
known and acted upon.
ON THE MANUFACTURE OF ARTIFICIAL FUEL.
BY E. F. L0ISEAU.
A Paper read before the American Institute of Mining Engineers.
Until June, 1868, it had not been
attempted, either in this country or
abroad, to manufacture, by mechanical
means, from anthracite coal-dust, artifi-
cial fuel for domestic use. Several at-
tempts had been made to utilize coal-
waste by converting it into a fuel for
manufacturing purposes, but none of the
processes were original, and they were
merely applications of the well-known
European processes and machinery,
slightly modified by American ingenuity
and mechanical skill. With one excep-
tion all those attempts have been failures.
The great difficulty in the application
of European processes and machinery
has always been the limited production
and the excessive cost of the manufac-
tured product, as compared with the cost
of mining and preparing the ordinary
anthracite coal for the market.
The only serious and intelligent at-
tempt to manufacture, on a large scale,
artificial fuel for manufacturing pur-
poses has been made by the Anthracite
Fuel Company, whose works are erected
at Fort Ewen, near Rondout, New York.
This company, organized under the aus-
pices of the Delaware and Hudson Canal
Company, had to go through the usual
course of difficulties, breakages and dis-
appointments, which seem to be- the lot
of every new industry. Thanks, how-
ever, to the energy and perseverence of
ON THE MANUFACTURE OF ARTIFICIAL FUEL.
545
Mr. L. L. Crounsse, a gentleman of
means, from Washington, D. C, the en-
terprise succeeded, and it is to-day estab-
lished on a permanent basis.
In order to increase the production,
and to reduce its cost, the Anthracite
Fuel Company was compelled to change
most of its plant, and to erect more pow-
erful machinery, producing lumps of a
larger size, almost twice the size of the
lumps made previously by the same com-
pany. This increase in the size of the
lumps has been resorted to in Europe as
well as in this country, in order to in-
crease the production; but the lumps, be-
ing large, require a strong draft for their
combustion, and consequently the use of
artificial fuel has been confined almost
exclusively to steamers and locomotives.
In order to manufacture a fuel which
could be used in all kinds of furnaces, it
was evident that the lumps should not
exceed a certain size, and machines for
this purpose were invented by Mr. Re-
vollier-Bietrix, of St. Etienne, France,
and by Messrs. Mazeline and Couillard,
of Havre; but the production of these
machines, in 24 hours, did not exceed 48
gross tons, in lumps weighing, each, one
kilogram, 2^0 grams. No better results
have been obtained in Europe to this
day, and no smaller lumps have been
manufactured there.
The compressing machines, above re-
ferred to, are constructed on the princi-
ple of Gard's brick machines in this
country. Circular horizontal tables, con-
taining either stationary or movable
molds, revolve under a pug mill, in the
center of which is a vertical shaft, with
knives placed at an angle. These knives
force the materials into the molds. The
bottom of the molds is formed by fol-
lowers, fitting exactly, which travel on
an inclined plane under the molding
table, gradually compressing the mate-
rials, and finally expelling the brick-
shaped lumps, which are afterwards re-
moved by hand, or pushed by a scraper
on a conveying belt.
The problem, therefore, was to obtain
a large production in lumps of a small
size, and my efforts for the last ten years
have been directed toward the solution
of that problem.
I devised and designed, to the best of
my ability, several machines which my
experience had told me were best
Vol. XIX.— No. 6—35
adapted to the continuous and automatic
production of lumps of a small size, the
main machine being the press. I had
previously made a good many experi-
ments, on a small scale, which had dem-
onstrated beyond a doubt the practica-
bility of the process. A good many
of our members will remember to have
witnessed in Mauch Chunk, in 1874, the
manufacture* of the fuel by a small
machine, which was the embryo of the
large one erected at Port Richmond. As
is usually the case, the large machine did
not work as well as the small one; it had
i to be modified several times, according
to what practical experience demonstra-
ted to be an absolute necessity. One
modification suggested another, until at
last, in spite of all the prophecies to the
contrary, I succeeded in getting the press
to work in a very satisfactory way. The
production is 137^- tons in 10 hours, the
lumps weighing but two ounces each.
I will give here a brief description of
the moulding press:
Two rollers, each 30 inches in diame-
ter, and 36 inches in length, contain on
their surface semi-oval cavities, con-
nected together by small channels, which
allow the escape of air and excess of
material, each cavity or recess commu-
nicating by four of those channels with
the surrounding ones. These cavities
extend in close proximity to each other,
in regular rows over the whole length of
the rollers, the recesses of every other
row being intermediately between those
of the adjoining row, in the nature of
the cells of a honeycomb, so that small
metallic contact surfaces are formed, and
the entire surface of the roller is utilized
for compressing the composition into
lumps of an egg-shaped form. The
shafts of the rollers are cast solid with
the rollers, and they are 10j inches in
diameter. Each roller weighs over a
ton. On top of these is a hopper, 36
inches long and 30 inches wide, in which
the materials to be compressed are dis-
charged from the mixer. In this hopper
a series of knives, screwed to a small
horizontal shaft, revolve rapidly, and
keep the materials in a granulated state.
When the materials to be compressed
happened to contain too much water
which was often the case, the mixture
was very plastic, and the lumps were
spongy and unfit for use. When the
M6
VAN nosteand's enoineeeing magazine.
mixture contained the required amount
of water, the rollers would spring, and
would deliver nothing but half-lumps.
Every means was resorted to in order to
prevent the springing of the rollers, and
to mold complete lumps. All sorts of
contrivances, suggested by able mechan-
ical engineers, were tried, without suc-
cess. Considerable time #was required,
and a large amount of money was ex-
pended to obtain the desired result. The
task had been given up by a good many
as a hopeless one, still I persevered. I
had observed that, when the hopper was
almost empty, the shaking of the rollers
stopped, and the half-lumps of the last
rows remained in the molds, instead of
being discharged on the conveyor below.
I concluded from this fact, that the
springing of the rollers was produced by
an excess of material above the com-
pressing point, and that if I could regu-
late the quantity of material a little
above that point, the springing of the
rollers would cease, and perfect lumps
would be produced. The thought was a
happy one. I devised several attach-
ments to regulate the delivery of the ma-
terials on both rollers, with only partial
success, until at last I concluded t6 muf-
fle one roller entirely with sheet iron,
and to deliver the materials on the other
one. In the centre, above the point of
contact of the two rollers, I placed an
iron gate, 36 inches long, 3 inches thick,
and 3 inches wide, guided at both ends
inside of the hopper, and working up
and down along those guides, by means
of two long bolts, threaded at one end,
passed through a stationary nut, fastened
in a wooden cross-piece above the hop-
per and worked by small hand-wheels.
By reducing or increasing the space be-
tween the bottom of the gate and the
roller, more or less material was carried
away by that roller. At the point of
contact between -the rollers, the materi-
als which have been delivered on one
roller are pushed into the cavities of the
other one, and perfect lumps are formed
and discharged on the conveyor below.
The difficulty is entirely overcome, and
the press has worked well ever since.
The coal dust accumulated in the yard
is on swampy ground; the tide- water
comes up to the middle of the lot, and
the capillary attraction draws the water
the coal-pile up as high as seven feet.
During dry weather we obtained from
the top of the pile coal sufficiently dry,
but when it rained the coal dust was so
wet that it clogged in the screen, in the
chutes under the chain elevators, in the
coal pocket and in the distributor. This
was remedied by erecting a gravel-dry-
ing apparatus, composed of two drums,
18 feet in length and 36 inches in diam-
eter, placed on an incline and heated un-
derneath. The drums revolve slowly;
the coal dust, as it comes from the yard,
is fed at one end of each drum; it trav-
els the entire length of the drums in five
minutes, while being kept stirred by sta-
tionary lifters, fastened inside of the
drums, and it is finally screened and dis-
charged at the other end perfectly dried.
In the drying oven we had the next
trouble. The first plan consisted in car-
rying the molded lumps through the
oven in 40 minutes, on five endless wire-
cloth belts, placed underneath each other,
and geared together, so as to travel in
opposite directions. The lumps falling
from the rollers on the upper belt were
conveyed into the oven at the speed of
12 feet in one minute, traveling the
whole length of the oven and falling
from one belt to another, until they
emerged from the oven on the lower belt,
to be discharged therefrom into the
waterproofing machine.
When the five wire -cloth belts were
loaded, the oven contained about six tons
of coal. Under the weight of the fuel
the belts would stretch, sag, and drop
the greatest part of the lumps on the
bottom of the oven, where they broke to
pieces. The belts were changed several
times, and replaced by others of smaller
mesh and stronger wire; additional roll-
ers were placed under the wire-cloth to
stop the sagging as much as possible,
but the belts would stretch in spite
of all, and the use of wire-cloth as con-
veyors had to be abandoned.
It was also ascertained that the fuel was
imperfectly dried, and that the contrac-
tion of the clay, used as a cement, could
not take place when the lumps remained
only 40 minutes in the oven. The solid-
ity of the lumps was found to depend
entirely upon the length of time during
which they remained in the oven, and
the following tests demonstrated this
fact to a certainty:
Three lumps which had been in the
ON THE MANUFACTURE OF ARTTFCIAL FUEL.
547
oven during 40 minutes supported a
weight of 99 pounds before being crushed.
Three lumps which remained in the
oven one hour and ten minutes stood a
weight of 148 pounds before being
crushed.
Three lumps which had remained in
the oven during six hours stood a weight
of 371 pounds before giving way.
Each one of these lumps came from
the same mixer, and contained the same
materials, and in the same proportions.
The problem then was not only to
modify the oven so that it would hold
sufficient fuel during six hours, but to
modify it in such a way that the fuel
could be discharged by its own gravity,
when sufficiently baked. To do this
seemed an insuperable difficulty. I
studied for weeks one plan after another,
until at last I conceived one which I
thought would answer the purpose. I
submitted the plan to competent author-
ity, and it was approved as a feasible
and practicable one.
The plan consisted in doing entirely
away with wire-cloth, in suppressing the
four lower conveyors, and in using for
the top conveyor sections of sheet iron
bolted to bridge links of malleable iron,
placed at regular intervals, in three end-
less link chains running in grooves and
moved by toothed wheels. The fuel was
to be removed from this top conveyor by
gates thrown slantingly across it, and it
would slide down iron chutes, forming
a, spiral, upon bars of wrought iron set
at an angle across the oven, and resting
upon cast-iron racks, placed at the lowest
point, 18 inches above the flue. Through
those bars and through the mass of the
fuel, the hot air was to pass and dry the
fuel.
When the fuel was baked it was to be
discharged by its own gravity, and
through a series of gates, on an outside
conveyor, placed alongside the oven, and
made of sections of sheet iron, bolted to
link chains like the top conveyor. This
outside conveyor was to dump the fuel
into an elevator, and from this elevator
the lumps were to be delivered into the
waterproofing machine.
The alterations described above were
made, and the whole oven became in this
way a kind of coal-bin, holding very near
one hundred tons of fuel.
When the oven, modified as stated,
was tried for the first time, it contained
nearly one hundred tons of good lumps.
It was heated to about 300° Fahrenheit,
and in about four hours the whole mass
of fuel was on fire. It required ten
men working two days and one night to
extinguish the fire. The fuel was en-
tirely spoiled, but no injury was done to
the w:il Is of the oven, or to the inside
fixtures of the same. In order to avoid
such an accident' in the future, the cast-
iron flues were covered with loose bricks.
Three times in succession the oven was
again filled, heated, and when it was sup-
posed that the lumps were sufficiently
baked, the discharge gates were opened,
and the fuel was found to be as moist as
when it entered the oven.
The oven was allowed to cool, and was
carefully examined by Dr. Charles M.
Cresson, of this city, and it was ascer-
tained by him that the openings for the
admission of air, and for the escape of
the evaporated moisture were much too
small. The fuel, as it seems, had simply
been submitted to a steam bath, instead
of being baked, and the defect could be
easily remedied, according to Dr. Cres-
son's opinion, by a false sheet-iron bot-
tom, which would bring the air in close
contact with the iron flues, and at the
same time prevent the fuel from catch-
ing fire by radiation from the flues. ' Dr.
Cresson advised larger openings for the
admission of air and for the outlet
of moisture. The sizes of those open-
ings have been carefully calculated, and
there is no doubt that when these alter-
ations shall have been made, the work-
ing of the oven will be as satisfactory
as that of the balance of the machin-
ery.
The waterproofing process has been
tried several times, and has been found
to work well. Instead of condensing
the vapors of the benzine, as was at first
intended, we were compelled, in order to
avoid accidents, to remove them by a
suction fan. These vapors pass through
a system of pipes; they are here mixed
with twenty times their volume of at-
mospheric air, so as to render them in-
nocuous, and they are then expelled
above the roof of the building.
It must not be forgotten that the pro-
cess applied, and the machines used,
were entirely novel, and considering all
the difficulties in the way of success, the
548
VAN nostrand's engineering magazine.
results obtained have been very satisfac- placed in a financial condition which has
tory. prevented the completion of the experi-
The large amount of money expended, , ment. In a few days, however, the finan-
the many disappointments which have ! cial difficulties will also be entirely over-
occurred, and, above all, the depressed ' come, a new company will be reorgan-
condition of the coal trade during the j ized, and I hope that in a few weeks the
last two years, have discouraged some of i works will be in successful operation,,
our stockholders, and we have thus been and the fuel will be in the market.
ON THE DISCHARGE OF SEWAGE INTO TIDAL RIVERS.*
By H. LAW.
From "Engineering."
The present paper is intended as a
contribution towards the important sub-
ject of the treatment and conservation
of rivers.
Mr. William Hope, whose name has
long been before the public in connec-
tion with this subject, in a recent letter
addressed to Engineering, makes the
startling assertion that the pollution of
the river Thames by the sewage is cumu-
lative; that is to say, in other words,
that there is no fixed limit to the per-
centage of sewage pollution, which must
go on in an ever-increasing ratio.
It is, therefore, of great importance to
examine this matter with some care, in
order to determine with exactness what
are the actual condition of tidal rivers
into which certain quantities of polluting
matter are discharged.
Now, a tidal river may be looked upon
as a reservoir of a very elongated form,
subject to the following conditions,
namely:
1. That it is supplied with water of
three different qualities, from three dif-
ferent sources, that is to say:
The water constantly draining off of
the surface of the basin forming the
watershed of the river, and that derived
from the land springs which find vent in
its bed; this we will designate river
water.
The water entering the mouth of the
river from the sea, under tidal influence,
which we will disgtinguish as sea water.
The polluted water discharged from
the sewers, which we will term sewage.
2. That the actual and relative quan-
* Read before Section G of the British Association :
Dublin meeting.
tities of these are not constant, but vary
within certain limits.
3. That the supply of sea water is not
constant, but intermittent, being poured
into the reservoir for a certain number of
hours, and then, for a certain period, the
reservoir being allowed to discharge a
proportion of its contents.
Now in the actual state of things the
river water may, and usually does, enter
the channel of the river by tributary
streams at various points, and the sew-
age may be discharged at many differ-
ent places, while the quantity of both the
river water and the sewage will vary ac-
cording to the amount of the rainfall
and other circumstances; but in inquir-
ing as to the ultimate degree of pollu-
tion of the river, we may simplify the
question under consideration, without in
any way invalidating the result, by as-
suming that the whole of the river water
enters by the upper extremity of the
channel, or elongated reservoir, and that
its flow is uniform and equal to the mean
quantity taken over a lengthened period;,
further, that the sewage is all collected
and discharged into the channel or reser-
voir at some intermediate point, and that
its flow is also uniform, and equal to the
mean quantity; furthermore, that the sea
water is poured in at the lower extremity
of the channel at regular intervals for a
certain period, and that the only dis-
charge of the contents of the channel or
reservoir is at its lower extremity, also
for a definite time, and in such a manner
that for a certain period in every twelve
hours the contents of the reservoir would
be accumulating, and, as a consequence,
the level of its surface rising, and that
THE DISCHARGE OF SEWAGE INTO TIDAL RIVERS.
549
then for a certain time, the contents
would be diminishing and the level of its
surface falling.
Xow, the subject of our inquiry is,
what, under the conditions assumed
above, will be the mean or average com-
position of the water contained in the
reservoir or river ?
In order to obtain a practical result,
let us investigate this question, adopting
the mean values for the several quanti-
ties which apply in the case of the river
Thames.
First, then, as to the extent and capac-
ity of the reservoir. The tidal portion
of the River Thames extends from Yant-
let Creek, where the jurisdiction of the
'Conservators commences, to Teddington
Lock, a total distance of 318,160 feet,
•or about 60^ miles; its breadth varies
from about 200 feet to 22,800 feet, or
about 4j miles at its mouth. Its super-
ficial area at high water is 58,182,380
square feet above London Bridge, and
1,054,362,660 square feet below the same,
making a total of 1,112,545,040 square
feet, or about 40 square miles. At low
water the superficial area above London
Bridge is 38,807,800 square feet, and
that below the same 681,786,610 square
feet, making a total of 720,594,410 square
feet, or nearly 26 square miles.
The mean range of the tide at the
mouth, that is, at Yantlet Creek, is 14
feet; at London Bridge 17 feet 4 inches,
and at Teddington Lock 3 feet.
The mean tidal capacity of the river,
that is to say, the difference in the quan-
tity of the water which is contained by
the river at high water and at low water,
with the above stated mean range of tide,
is 616,634,400 cubic feet above London
Bridge, and 13,562,903,900 cubic feet be-
low the same, making a total of 14,179,-
538,300 cubic feet.
Now, as has been already stated, this
body of water is derived from three
sources, viz., the sea, the land drainage,
the sewage: and it is necessary in the
next place to ascertain the relative quan-
tities furnished from each of these sources.
The downward flow of the Thames at
Seething Wells, near Kingston, a short
distance above Teddington Weir, and
beyond the influence of the tides, was
gauged daily for eleven years by Mr.
Taylor, and the result obtained was an
average annual discharge of 500,000
millions of gallons, which, reduced to a
mean daily flow, would equal 1,369,800,-
000 gallons. This is, however, the drain-
j age of only 3676 square miles, whereas
| the whole area of the Thames Valley is
; 5162 square miles; and if we assume, as
may very fairly be done, that the quan-
! tity discharged from the lower portion is
| in the same proportion, we shall have for
i the total mean daily discharge from the
drainage of the Thames Valley 1,923,-
: 626,000 gallons, a quantity which, we
may incidentally remark, is about one-
third of the rainfall.
From the above, however, must be de-
ducted 100,000,000 gallons, which is daily
abstracted from the river above Tedding-
ton Weir, for the supply of water to the
metropolis, leaving a total quantity of
1,823,626,000 gallons, or 291,780,160
cubic feet for the mean daily discharge,
being 145,890,080 cubic feet as the mean
quantity of river water contributed each
' tide.
The mean quantity of the sewage dis-
charged into the Thames from the two
1 outfalls at Barking and Crossness may
be taken at 120,000,000 gallons daily,
equivalent to 9,600,000 cubic feet every
! tide, making with the river water a total
of 155,490,080 cubic feet, which being
deducted from the mean quantity already
stated as that which enters the river
! every tide, we have 14,024,048,220 cubic
: feet as the mean quantity of sea water
which enters the Thames every tide.
It is difficult to form a true idea of
the relative values of such large numbers,
and, therefore, it is better to reduce them
1 to a percentage, when we obtain the fol-
lowing result namely, that the mean
composition of the Thames water is as
follows, namely:
Sea water 98.91
River water 1 .02
Sewage water 07
100.00
That is to say, the actual mean quan-
tity of sewage in the tidal portion of the
River Thames, extending fromTedding-
S ton to Yantlet Creek is only 0.07 per
cent., or otherwise expressed, only one
1477th part of its whole bulk.
Futhermore, it must be borne in mind
| that owing to the circumstance of the
i river water always being delivered at the
| upper end of the elongated reservoir, no
550
van nostrand's engineering magazine.
less than sixty miles in length, while the
ultimate discharge is wholly from the
lower extremity, the composition of the
water varies greatly, being always much
freer from sea water and sewage in the
upper portion than the lower. In point
of fact, it must be evident that in the
case of a stream which has a certain
quantity of river Water, that is, as we
have already defined it, water derived
from the rainfall and discharged into the
river by surface drainage and land
springs, there must always be a point,
even in the tidal portion, above which no
contamination can exist from sea water
or other matters which enter the river
near the lower portion of its course.
The foregoing is a statement of the
average result, the actual amount of con-
tamination by sewage at any given time
and place must depend upon the recent
past rainfall and upon the state and con-
dition of the tides, but at no time and
under no circumstances can the amount
of the sewage contained in the Thames
water be raised sufficiently above its av-
erage value of one 1477th part to pro-
dure any appreciable pollution, far less
to afford any ground for the statments
to which previous allusion has been made.
Generally, it is obvious that considera-
ble care should be taken in the selection
of the points of discharge of sewage
matter into tidal rivers, and of the times
and conditions of such discharge.
One of the most essential of these
conditions being that the sewage shall
be so discharged as to be carried into
the main stream, in such a manner that
it may be commingled with a sufficient
bulk of water; and that water traveling
with sufficient velocity to insure no de-
position by precipitation of any of the
contained matter being possible.
Again, the point selected should be
one where the course of the stream is
direct, and not subject to eddies, or sets
upon either of the shores; so as to in-
sure the thorough absorption and mix-
ture of the sewage with the main bulk
of the river, and to prevent any deposit
taking place upon the foreshores.
Where populous places exist upon the
banks of the river, it is, of course, nec-
essary that no sensible pollution of the
stream from sewage matter should be suf-
fered in the neighborhood of such place,,
and in most cases there are two modes of
obtaining this result, namely, by the re-
moval of the point of discharge to a suf-
ficient distance below the town, and by
the discharge of the sewage during only
a limited portion of the ebb tide. To
effect the first objed, it will be necessary
to construct sewers probably of a con-
siderable length, and to effect the second,,
to form tanks of sufficient capacity to,
permit the sewage to accumulate during
the intervals between the times of dis-
charge.
It is obvious, therefore, that there is
an ample field for the skill of the engi-
neer to be exercised, in so designing
works for the discharge of sewage into
tidal rivers, as to fulfil in a perfect man-
ner the foregoing essential conditions,,
and that it is under 8uch conditions only
that such discharge should be permitted.
THE INFLUENCE OF SILICON ON CAST STEEL
By M. POURCEL, of Terre Noire.
From "Iron.
The following note was communicated
to the Societe de 1'Industrie Minerale, at
the September meeting. " The writer
begged to recall the attention of mem-
bers to the subject of cast steels, homo-
geneous and free from blow-holes, which
was discussed at considerable length at
one of the Paris meetings, when differ-
ent opinions were advanced as to the
advantages and disadvantages of obtain-
ing these steels, more particularly with
reference to quality, either by mechan-
ical or chemical means. In the first
place, if the gas is prevented from escap-
ing from the steel, and consequently the
blow-hole from forming, we shut up the
wolf in the sheep fold — so M. Griiner
affirms (ou enferme le loiip dans la
THE INFLUENCE OF SILICON ON CAST STEEL.
551
bergerie) — which is certainly a disadvan-
tage.
But does this disadvantage really
exist ? The wolf is the oxygen, or
rather the carbonic acid, and when a
bath of steel has been previously deox-
idised by the addition of sufficient man-
ganese, and the perfect malleability of
the metal when hot, has been assured
before casting, by means of test samples,
it may be taken for granted that it no
longer contains oxide of iron, except the
merest trace. But nevertheless, at the
moment of solidification, the steel gives
off carbonic oxide gas; and whether this
gas exists in solution, or whether it
arises from the intermolecular reaction
of the carbide of iron of the steel on the
oxide of iron, which is formed during the
action of casting, it is not less the cause
of the silvery blow-holes so frequently
met with in blocks of steel."
The theory of these reactions put for-
ward by the writer, at the November
meeting, 1876, was based on most care-
fully observed facts, and no new fact has
come to light up to the present time to
contradict it. Whatever mechanical
means may be employed to prevent the
formation of the blow hole in the mass
of steel at the moment of its solidifica- 1
tion, if the metal has been deoxidised
before casting, and contains an excess of
.2 per cent, to .5 per cent, of manganese,
it is certain that the quality will in no
way be altered, and that the result will .
be most satisfactory. In the second
place, another opinion advanced by Mr.
Vicaire, gives the preference to mechan-
ical action over every chemical reaction,
as the former introduces no foreign ele-
ment into the steel. Mr. Vicaire is of
opinion, for instance, that the silicide of
manganese added as the chemical reagent
to prevent the formation of hlow-holes,
affects the qualitit-s of the metal, by
leaving in it a foreign element, namely,
silicon, although in very small propor-
tions, say .2 per cent, to .3 per cent. In
this case, let us examine to what extent
the metal is affected — if at all. The
writer sets aside the possibility of obtain-
ing practically a metal free from silicon,
a question of considerable interest, and j
upon which he touched in speaking of
the " influence of the nature of the pots
used in the manufacture of cast (crucible)
steel, of the chemical composition of the
steel," at the July meeting, 1877. It
may be mentioned :
(1) That the best brands of English
tool steel, made in crucibles from
cemented Swedish iron, rarely contain
less than .1 per cent, silicon, and gener-
ally from .1 per cent, to .3 per cent. (1)
That Krupp's cast steel, according to the
analyses of M. Boussingault, contains a
remarkable quantity of silicon, .3 per
| cent, to 5 per cent.; and (3) that French
I cast steels in no wise vary in this respect
from similar English steels; and lastly,
I that the metal which for so long was
I considered the ideal of steel, was never
j free from silicon.
We have, therefore, only to examine
i whether two steels, differing only in their
j chemical composition by one or two
| thousandths of silicon, really show any
j wide difference in their physical and
| mechanical qualities. All the experi-
! ments that have been made in various
| quarters to determine the action of sili-
i con in steel, have led to the same conclu-
i sion, namely, " that it plays the part of
! carbon, although less energetically,"
! Swedish chemists agree on this point,
and Mr. Akerman, whose opinion is
highly valued in Sweden, considers that,
in order to obtain steel of the mildest
description, the silicon as well as the
carbon ' should be eliminated. The
writer also holds this view. Only traces '
of silicon are allowed to remain in plate
steel manufactured at Terre Noire. An
examination of " Experiments on the
Qualities of Plates," published by the
" Jernkotoret " of Stockholm, will show
that Terre Noire Siemens-Martin steel
plate contains : Carbon, 0.20 per cent.;
silicon, 0.025 per cent.; phosphorus,
0-08 per cent.; manganese, 0.235 per
cent.; and sulphur, 0.02.
The action of silicon may be classed
with that of the hardening constituents
of steel — carbon and manganese; but
compared to that of carbon its influence
is slight.. Professor Mrazek, whose
work on this subject has been published
in the Bulletin tie V Industrie Minerale
concludes from his experiments that, as
far as manipulation in the hot state is
concerned, the effect of silicon is three or
four times less than that of carbon; and,
similarly, Mr. Mussy states in a commu-
nication to the Bulletin, that ingots had
been manufactured at his works contain-
552
VAN NOSTRAND's ENGINEERING MAGAZINE.
ing as much as 2 per cent, silicon, but
little carbon and manganese, and had
undergone, without difficulty, the neces-
sary hammering and rolling for plates
and similar articles. The writer must,
however, express surprise at Mr. Mussy's
statement that the steel in question con-
tained but little manganese: he can
hardly understand how a cast metal con-
taining I per cent, of silicon only, even
with very little carbon, can stand the
work of the hammer, unless it contains
.6 to .8 per cent, of manganese.
Assuredly a metal containing 2 per
cent, of carbon would act very different-
ly. Consequently, under ordinary cir-
cumstances, when the percentage of car-
bon permits of easy manipulation when
hot, i.e., when this percentage of car-
bon remains between .1 per cent, to .9
j^er cent., or even 1 per cent., the pres-
ence of an additional .1 per cent, or .2
per cent, of silicon cannot affect to any
extent the malleability of the metal in
the hot state.
But is there any necessity for examin-
ing the behavior in the hot state of a
metal destined for the production of
castings which have to undergo no ham-
mering, but simply finishing in the lathe
or planing machine ? It appears rather
that the question should be confined to
determining whether the presence of
silicon within the specified limits of .2
per cent, or .3 per cent, influences the
mechanical properties of the metal, its
resistance to shock, tensile strain, crush-
ing strain, etc. Professor Mrazek, who
has made experiments to determine the
tenacity of the metal cold, admits that
T4¥ths per cent, of silicon do not diminish
the tenacity more than -^th per cent, of
carbon. Amongst the thousands of tests
for tensile strains and resistence to shock
made at Terre Noire, on cast steels con-
taining at least .1 per cent, of silicon,
and at most .4 per cent., one fact has
been established,. namely, that two steels
containing equal quantities or nearly so
of carbon, manganese, and phosphorus,
both being equally pure, and differing
only by .1 per cent, to .3 per cent, of
silicon, give mechanical results differing
but slightly. That containing most sili-
con shows rather less elongation but
higher tensile strain, and behaves as if
it were slightly more carburized. With-
out attempting to fix an exact law, it
has been observed that the increase of
tensile strain given by .1 per cent, of
carbon amounts to 6 kilos per square
millimetre on the average; whilst the
increase due to .1 per cent, silicon
scarcely exceeds 1 kilo, and that the
difference in resistance to shock is
scarcely appreciable with variations of
.1 per cent, to .3 per cent, of silicon.
It remains to be examined whether the
properties of annealing and tempering
are influenced by the presence of silicon.
The researches of Colonel Caron, on the
behavior of silicon in steels, has proved
the property of this body to displace, at
a red heat, the carbon from its combina-
tion with iron.
Colonel Caron has come to the conclu-
sion that in steels containing silicon — he
does not say how much — the carbon,
after several heatings, passes into the
graphitic form, and that the metal, con-
sequently, loses the property of temper-
ing-
Silicon, as shown by Mrazek, affects
the tempering property but very slightly,
its influence in this respect, as compared
with carbon and manganese, is hardly
appreciable. This is a very favorable
property, and entirely precludes the fear
of the metal being rendered fragile on
tempering by the incorporation of a few
thousandths of silicon. As regards the
effect of silicon in diminishing the tem-
pering properties of the steel after
repeated heatings, its influence might, no
doubt, be injurious in tool steel.
A tool will lose its hardness more or
less rapidly in its work, and one of the
chief qualities of tool steel is the faculty
which permits of its being tempered and
softened almost indefinitely. But this
objection almost vanishes when we come
to consider the steel required for castings
of large dimensions, which require no
hammering. It is a matter of slight
importance that this metal should have a
tendency to lose its tempering power
after a certain number of heatings;
besides, the proof of this tendency is
still wanting.
In fact, it must be borne in mind that
the conclusions arrived at by Colonel
Caron were deduced from a limited
number of tests made on a particular
metal, where carbon and silicon were in-
corporated alone in the presence of each
other, in the absence of manganese.
THE CONTINUOUS GIRDER WITH EXAMPLES.
553
Now, in steel castings of large size, man-
ganese is always present, and its pres-
ence modifies the tendency of silicon to
diminish the amount of carbon combined
with the iron. The writer adduces, as
an instance, a pig-iron containing 3 per
cent, silicon, 2 per cent, carbon, and .1
per cent, to .2 per cent, manganese,
which showed a grey fracture with the
carbon in the graphitic state, and a sud-
den cooling, failed to effect the solution
of the carbon. Cast into an iron mold,
it took no chill. As soon, however, as
the amount of manganese is increased,
the effect of the silicon is partly neutral-
ized, and when the proportion of these
two bodies is that of the equivalents
qt-, the grey specks in the fracture dis-
ol
appear and it becomes perfectly white.
As a rule, pig-iron containing silicon and
manganese in the specified proportions,
takes chill "in proportion to the per-
centage of carbon," as an ordinary pig-
iron free from these bodies. If the same
observation be applied to the case of
steel, it will be readily understood why
a metal containing at the same time sili-
con and manganese, in definite propor-
tion, may show results differing from
those obtained by Colonel Caron, and
may acquire by tempering all the quali-
ties of superior metal.
As regards the proportion of manga-
nese to be left in the steel, it will vary
from .2 per cent, to .5 per cent, for .01
per cent, to .35 per cent, of silicon.
This law is equally applicable to phos-
phorus. A good idea of the changes of
| grain of solid cast steels, under the in-
i fluence of tempering, may be obtained
! from the fractures exhibited in the Terre
j Noire Pavilion at the Exhibition; the
, detailed catalogue of each sample gives
all the figures of the results obtained
from mechanical tests before and after
tempering, as well as the chemical com-
! position.
We may, therefore, reasonably con-
1 elude that the presence of silicon to the
extent of .1 per cent, to .3 per cent, in
solid cast steel obtained by chemical
j reaction, affects neither its physical nor
i mechanical qualities. Recourse must be
| had to infinitely small quantities {/aire
1 valoir des infiniments petits) to deter-
1 mine the difference existing between
| this steel and steel obtained without the
i addition of silicide of manganese by any
! mechanical process whatever.
A DISCUSSION OF THE CONTINUOUS GIRDER WITH
EXAMPLES.
By M. S. HUDGINS.
Written for Van Nostrand's Magazine.
In the year 1825 Navier first an-
nounced the now well-known principle,
that the extension and compression of
the fibers of a beam on both sides of the
neutral axis, or more correctly, the neu-
tral plane were proportional to their
distances from the neutral plane. From
this he deduced the equation of the
elastic line, and applied it to the con-
tinuous girder of special form.
In 185 7 Clapeyron made known his
celebrated theorem of the three moments;
that is, the consideration of the moments
over the piers, and the formation of an
equation between the moments over any
three consecutive piers. He applied it
only to uniform loads over a whole
girder or span. The theory of continu-
ous girders is considered to be due main-
ly to Clapeyron. This publication at-
tracted the attention of the mathema-
ticians to the subject, and it has since
been greatly improved, but Clapeyron
may be considered as having made the
foundation for them all.
In 1862 Winkler gave a general theory,
and in the same year a like work was
given by Bresse. Winkler, in 1867, put
forth a general theory with suitable
analytical formulae thus extending his
former work. Weyrauch, in 1873 pub-
lished the fullest and most complete
work on the subject, leaving little to be
added or desired. The French and Ger-
554
VAN NOSTRAND'S ENGINEERING MAGAZINE.
man mathematicians have done most of
the work in this department of applied
mathematics, very little having been
done by any others.
Before going into our subject we will
introduce without demonstration the
simple formulae for curvature, slope and
deflection, as they will come in farther
on in the discussion. Their proof can
be found in the ordinary books on ap-
plied mechanics. Let r be the radius of
curvature of the beam, M the moment of
resistance at any cross-section, and I the
moment of inertia. Then we will have
1 M
-=_,._, E being the modulus of elasticity.
The maximum value of r can be found
for any particular load by the substitu-
tion for M of its value for such load, and
then applying the maximum and mini-
mum test. Let i be the slope of the
beam at any point, and i0 its slope at the
/x'dx
— . If there is
o V
/x'dx
— -'.(I). The
steepest slope under a given load W is
M'"vW
i. — t, . T 7 , found from (1) by intesrra-
tion and proper substitution. W is a
factor depending upon the distribution
of the load, manner of support, and form
of cross-section, c—l or 21 as the beam is
supported at one or both ends, n' =
-— (I/*), b the breadth and h the depth
of the circumscribing rectangle. The
mode of calculation of m" will be given
in the examples.
/%'
idx (2) under a
n'"Wcz
given load W, v= -^—-y-? (2') as found
from equation (2). n1' depends upon
the distribution of the load, mode of
support and form of section. It will be
calculated in the examples. There is
much similarity between these formulae
for slope and deflection.
In discontinuous beams the calculation
of the shearing force, bending moment,
curvature, slope and deflection are direct
processes, going step by step from the
calculation of one of these quantities to
that of another. In continuous beams
the process is one of elimination between
these quantities. A beam is in the state
of a continuous beam when a pair of
equal and opposite couples act on it in
the vertical, longitudinal, sectional planes
at its points of support, of such magni-
tude as to maintain its longitudinal axis
horizontal there. In the figure let CC
represent a beam supported at C and C
and so fixed as to have its longitudinal
axis horizontal at those points instead of
having the slope i which it would have
were it not fixed or continuous.
At each of the points C and C there
is a uniformly-varying horizontal stress,.
a thrust below and pull above the neutral
plane; the moment of this couple is
equal and opposite to the moment of the
couple maintaining the beam horizontal
at C; knowing that moment we can find
the stress on the material ; then the
effect on the curvature, slope, deflection
and strength of the beam.
To do this we proceed as follows: —
Determine the slorje i, which the beam
would have at C were it not held hori-
zontal there under the constant moment
M„t/= / - dx— I ■=Tr1dx=-~-1 and
° ' J 0 r J 0EI EI
Eft
M^— — \ This value of Mr is the
moment of the stresses in the beam at
the point C. Since it tends to produce
convexity upward we call it — M^ The
load on the beam will tend to produce
convexity downwards. Let M be the
moment of flexure at any point of the
beam were it simply supported at C and
C. The actual moment at any point
will now be M— Ma. The substitution
of this value for M in the formula? for
curvature, slope and deflection will show
the change in these quantities produced
by making the beam horizontal over the
points of support or making it continu-
ous. Where M is greater than M, the
beam will be convex downwards, where
less, convex upwards; where M=M1 the
moment of flexure, and consequently the
curvature vanishes; these are called,
points of contrary flexure; at these points
thebeam is subject to shearing force
only.
(Ex. 1). Let us apply these principles-
to a beam of uniform section symmetri-
THE CONTINUOUS GIRDER WITH EXAMPLES.
555'
cally loaded. Our formula for the slope
. m'"Wc2 2m"mWc* „,. .
gives i.= ^ ,773 .= „ ,. .-=- ,m' 'being
= 2m"m, where m=M0-rW/(3)M0 being
the maximum bending moment in a free
beam. We have found M = — l=
c
alW>h\ . T ,.., , .. ,
since L=n oh see eq. (1 ), sub-
stituting for i1 its value, M] = 2ra"raWc
=m"mWJ=ra"M0 from eq. (3).
"We have now to determine m". The
value of » the slope may be written
«*=/
MI0 M
mWI /*c MI
-°C?SC:
Ew'M
,/
IM
Clx:
M0 />MI(
EI/ IM(
m~Wl
— n
En'bh9
dx
I0 being the max. moment of inertia,
MI
=r~- is a numerical ratio, and m" is the
IM0
sum of the various values of this ratio,
or m"c--
f
MI,
.IM,
dx. In this case M=
W. M.
cW
and the beam being
of uniform cross-section ~ = 1, and jjy
1 JM„
1-
a;
1, ^
<\
:M.-rWZ=
1
dx=ic .*. m"
w= j,
2mm" =J. Let M/ be the actual bending
moment at D. Then M0/ = M0— M1 = M0
— tw//M0 = (1— m") M0. The greatest
moment of flexure must be either at D
or C, or at both if they are equal, but
for a uniform section, m" is never less
than \ .'. the greatest moment may be at
C or at 0 and D together, but never at
D alone.
The deflection is found by subtracting
that due to the uniform moment M.1 from
that which the beam would have were it
simply supported at C and C. We pro-
ceed thus : The deflection as found in
eq. (2') is
n"'Wc' 2»m"Wc'i
v =
En'bh9
Eiib/i'
M,
the deflection the beam would
EI
have were it simply supported at C and
0. This must be diminished by the de-
flections due to the uniform moment M2.
The curvature due to that moment is
1 M, , . . p*dx r
r=m •'• the slope 1S t=v ~v=«/
o EI
dx=^~, and the deflection v'= / i dx-
EI' *s o
/>cMx , M.c2
/ ^ dX:
EI
2EI
n" being taken equal 2mn" where m has
been explained, and n" will be found
farther on. mWl = M0 and oifbhz—l
n"MJ , -f M,
but Mn=— rr .'. V = —r.
EI
Now the true deflection of the beam
equals v — v =vl=-l —, — $ \^T~ equals,
(since M, =1/1" M0), \n"-~ \
M/
EI
From this we see that by fixing the
ends or making the beam continuous it
is made stiflier in the ratio n" to
in" r, n" is obtained as follows,
v=fi dx which from equation (4) can be
/• /-MI0 M0 _ 2 mWl
written v=J J ^-. ^ dx*=
MI
IM0 EI(
MI0 _ a mWl
idx =^ ,, ..wc
MX
E?i'bh3
En'bh*
, ^dx*. Now in this case, as has been
Ml '
V. MIo 1
shown, g-j°=l
= /./.
H\
\--\- dx'
3°
and as
2?n?i", but m has been shown equal
to ^ in this case .'. n'
flexure is
c—x
The actual moment of
M--M]=M-m,/M0=M-iM0=M
_W(c-2x) 1_M _ W(c—2x) _
4Wc- - --gj- 4EI r~
4EI 1 _. . ,rt, .
I he point at which ?• is a
W ' c—2x
maximum can be
#-
8EI 1
dr
dx
found thus ;
2, putting it equal to o we
W (c— 2x)
get x=^c. The point at which r is a
maximum and, consequently, the curva-
ture a minimum. The points of contrary
flexure are found by solving the equation
M— M=o or W — |Wc=o whence
1 2 4
x—\c^ therefore as we should have ex-
556
VAN NOSTRAND'S ENGINEERING MAGAZINE.
4EI( )'-
pected the points of flexure are points of
minimum curvature. The slope i= I
~7~J 0 4EI
We will now determine the equation
of the elastic line and apply it to this
particular case. We have for the radius
of curvature -=-==, or EI-=M (5) but
r El r v '
from the formula for the radius of curva-
ture we have r=-{ 1 + [—- ) \-2 . but the
cPy
dx'
V
curvature being very small •] ~
be neglected in comparison with unity
1 1 d*y , . .
•"' rT. IS) or r~dx2 substltutmg tms
dx*
value of - in equation (5) we get EI
d*y
~ t = M. The equation of the elastic
line in cartesian coordinates. The value
of M for this case as has been shown is
Wc Wcc
— — . Substituting this in the eq.
of the elastic line we have EI^h(=
dx* 4
Wx d2y 1 (Wc Wx) .
~ °r d^=M\ T ~ — l ^grating
%_J[_jWc _W
daf~El ( 4 X ~~T
^ dy . . ,
^i-j tne tangent of the angle made
dy_ 1_
dx~m
( Wc W*2 )
1 4* 4~j + '» integrating again 2/=
1 j Wc 2 W 3 )
-gr 1 — -I — + r -M^ a construc-
tion which disappears by making y=o
when x—o.
If now the beam is horizontal at the
origin, or perfectly continuous, t^o and
the
found. Placing
— o we find =
4 2
+ C0 making x=o
o or &= —
dx
d*y
by the tangent at the origin
eq. of the elastic line is Y=
EI
W. Let us now find the
j(3^ X* )
points of inflection of this curve and see
if they agree with the points already
co and does
d ?y
not apply. Now substituting in f
respectively-^ — +h >-and-j — — h >• we find
it changes sign .*. at x—— there is a point
of inflection as has been shown by the
solution of the eq. M— Mx = o. Solving
dy ,
the eq. -f-~° %=c .'. the point or max.
deflection is at the center as would be
expected. After having found the
points of inflection A and A, the beam
can be treated as though it were com-
posed of three simple beams. First, as
a beam CA fastened at 0 and loaded at
A. Second, as a beam ADA supported
at both ends A and A. Third, as a
beam AC fastened at C and loaded at A.
And the slope, curve and deflection may
be found by the solution of these cases
of simple beams. In the same way if
the beam extended on over other piers it
could be revolved into simple beams, and
discussed as in the corresponding cases
of simple beams.
We now come to the fundamental the-
ory of continuous girders known as the
theorem of the Three Moments, with the
load distributed in any manner what-
ever.
Let x=o, y=o and x=l, y=o be the
co-ordinates of two adjacent points of
support, x being taken horizontal. Let
the vertical forces be positive down-
wards, at any point x between these two
points of support let to be the intensity
of the loading per unit of span, and EI
as before the product of the modulus of
elasticity and moment of inertia, all of
which may be uniform or variable, con-
tinuous or discontinuous.
The following double and quadruple
integrals will come in for which we will
use the following symbols, viz.,
J J wdx =mJ J m=nJ J kT?
Let the lower limit be x=o. When
the integration extends over the whole
THE CONTINUOUS GIRDER WITH EXAMPLES.
557
span, denote it by affixing 1 as nl9 q^.
Let — F be the upward shearing force
near the point of support (x=o), M0 the
bending moment, and T the tangent of
the inclination at the point of support.
At any point x of the span, let M be the
moment.
Now the sum of the moments of all
the forces acting on the beam must be
or. 2(ms) = ihsLt sum=o = M0-F + M-M.
.-. M=M0— F»+«i (6)
To find the deflection y, we have from
the equation of the elastic line
(Ty 1 ,_ 1 _ 1
a?=iaM«-MI"+HTO
integrating between o and a,
dy fxclx f*xdx
dx 0J 0EI J 0 EI
integrating again —
ujxfxdx'
we get-
mdx
f
y-
oEI
Ei
rr
mdx*
+ T,
or using the symbols above given,
y-M0n-Yq + v+Ta (7)
Now let Mj be the moment at the far-
ther end of the span, then substituting
it for M in eq. (6),
F= M.-M, + "», (8)
And since at the farther end y^o
_ Fq^—m^-
l
{!-?}=
MA-£
by t the tangent of the angle made by
the neutral layers when the continuity
is not perfect, there will result,
0 = M0 [qp+ £_! r-nfln) -n-ilT) -
-M_! q-i r + m&F + nd ?_i P—Vfln
-y^vr-trr (n)
which is the general theorem of the three
moments. As it is an eq. expressing the
relation between the moments over three
adjacent piers, M0 being the moment over (
the pier at the origin, and Mx and M_i
| being the moments over the adjacent
piers on the right and left.
A continuous girder of n spans has
(n — l) such equations and (n— 1) un-
known moments, the moments at the
endmost piers being zero, hence, we can
T by elimination, find the value of all
+ I these unknown moments. When the
number of spans is large the elimination
would be tedious in practice. But
Clapeyron has introduced a system of
1 multipliers called the Clapeyronian num-
bers which makes the elimination com-
paratively easy. They are such numbers
that the eqs. when multiplied by them
and added, all terms containing the
moments disappear except one, which
can be found directly, then by the same
process the other moments can be foundo
Having found the moments, the inclina-
tion T can be found by eq. (9). The
shearing force at the origin by eq. (8).
The deflection by eq. (7) and the moment
at any point in the span by eq. (6). The
points of max moment can be found by
solving the eq. 7- =o and of max. de-
(9)
£
"*" r \v
Consider now an adjacent span extend-
ing from the origin (x=o) to x— — i in
the opposite direction to the first.
Let the definite integrals for this span
be designated by affixing —1, as ra_i,
n—\. Let — T' be the slope of this span
at the point of support, then will be ob-
tained just as before,
1 wL_i ) M_!^_i
T'- Jg"1 n~1 j -
1 "°| r v f
m__i q_i
Adding equations (9) and
clearing of fractions, also denoting T— T'
(10) and
dx
flection from the
dy
e* dx=°>
and in the
same way the other points of max. or
min. change of any of the functions may
be found.
(Ex. 2). The application of these
formulae to a continuous girder of any
number of spans of equal lengths, alter-
nate spans being heavily loaded i. e.,
(bearing a load besides the weight of the
bridge) will illustrate their use, M=
wx
X
V:
EI
6EI •-24E1, — ^iDg taken
2x>
constant for the whole girder,
for a complete span x=l, for heavily
558
VAN NOSTRAND'S ENGINEERING MAGAZINE.
loaded span w=w0 + wl9 lightly loaded
w=w0, n and q are the same for both
heavily and lightly loaded spans. Notic-
ing these points we now proceed to the
solution of our eq. (ll), and on account
of similarity of circumstances over each
pier,- the moments over them all are
equal or M0=Mx=M_i and so for the
others.
Reducing eq. (11), q1 and q—\ cancel
being taken between +1 and — £, and
since m11 = 2VJ and rnq_\ q—\ =2V_i l.t
The result is 0= — 2M0«]+V1 + V-i —tl,
or
M
_V1 + V_i -tl
24EL
2nl
24EI
(w9 + wy i EL-tj =2H«l±!£iE_+?ei
24
EI
If now we suppose the girder perfectly
continuous t—o and M0 = — °- l- F (12).
For simplicity t will be regarded as zero
or the beam perfectly continuous in the
remainder of the calculations.
The shearing force F:
M0— Mj + jw,
For lightly loaded span M=2™°**V--
w.lx wnx* .
~ — I — — , max. moment at the center^
2i 2
I ^F° [ p- The defleotion y=M0«-
Fq+y+Tx=2w°±?>lV
Wn + W.
48EI
w
I
6EI
l_x <Ml_ 2^o+^ »_
48E1 ' efr 24EI
_ xr= -°J or (^0 + wi)o ^or ^gnt an(^ heavy
loads. The slope T:
F^-M^—V,
I
"jl2Er~48ET 24EI j ' * "
EI 24EI j
w /
48EP
w0l* 2w0
12EI 48EI
f
-z-l= l^j. agreeing with the supposi-
48E1
tionT + (-T.)=^I+)-^} =
o. Moment at any point in heavily load-
ed span =M=M0-F* + m=2^*V-
w.
f7M
' dx
wn 4- w,
* +
+ 24EI ^
iir*8 + isir* +48Er0'*=2 sat,s-
fies the eq. and we know from other con-
ditions that the max. deflection is at the
center, hence we need not discuss the
cubic eq. but substituting »=-- in the
z
value ,of y there is obtained the max. de-
flection for heavily loaded span. To find
the same for lightly loaded span we
have only to replace w0 -f wx by wQ.
In this case we will apply the principle
used in the first example for finding the
moment over the piers to see if the two
results agree. The actual moment ==M,
— Mj, M being the moment were the
beam free, and Mx the constant moment
over the piers. Take the origin at the
center of the span, c=—. Let x be the
abscissa of a heavily loaded span, and »'
of a lightly loaded one.
M=^+3(c8_a!,
for heavy load, and
w,
(c*-v'2) for light load. .*. The actual
moment for heavy load^M7:
(C2_V)_M1? and for light
!^(^_^)_M1 slope i=y^-d^=
w, + wl
{w0+ W,) X = OX:
The maximum mo-
ment is at the center; substituting this
value of x in the equation of the mo-
,, 2wn + «>,„,
ment, the max. moment JM= — —t — 7 —
24 m
w. + 2w,
24
\>-
ii I !Eir2lV'-T) M^ \ (heavy) and
m I f ^'"S ~M^ \ for light load-
The beam being continuous i1 for x=c
and x=—c, should be the same, equating
the two values, we have
THE CONTINUOUS GIRDER WITH EXAMPLES.
559
or — °-^— 1c3=2M1c, Mx= — ^--'c2
o D
which agrees with the value of Mt ob-
tained from the general formula. Points
of inflection can be found by solving
cPy . „ .
-r^=o or oo , or by means or the equation
M— M=o, in either case there will result
a quadratic equation giving two points
in each span.
(Ex. 3)
A0 A/ A^
ln- 2
Aa_i
at a2
Qo Q, Q2
an— 1 &n
Qn— 2 Qn— 1 Qn
Let A0An be a continuous girder, A0A1
etc., points of support or subject to the
action of isolated loads, Q^ etc., posi-
tive upward action of piers or negative
downward action of loads. Consider a
section normal to the elastic curve in the
span An_x An_i ax a2 . . . the lengths of
the divisions j30 (5x . . . the angles made
by the girder at the piers with the
horizontal line, w the intensity of the
loading. Then the eq. of the elastic line
EI g- = M becomes EI g = J (a, + a2
+ . . . . +an_i + x)\o — (a1 + a2 + . . . +
«n_i +x) Q0 — (aa + «3. . . +«n_i + #) Qa
— # — («n-l +3?) Qn-2 — «Qn-l, *
being the distance of the section from
An_i ; reducing these results,
+ ...+«n_i) ivx + livx*— aaQ0— a2(Q0 + Q,)
-«,(Qo + Qi + Q9)- -«n-i(Q0 + Q1 + -
+ Qn-a)-*(Q0 + Ql + ... Qn-l).
Integrating EI j ~ —tan. /?n_i f = J («,
+ fl,..+«n-l)2ra + |(fl1 + a + 2 + ...+fln-l)
^2 + iio^-[a1Q0 + a2(Q0 + Q1)+a3(Q,+
Q, + Q2) + + On-l(Q0 + Qx + Q. + •••• +
Q,_2)]^-KQo + Qx..» + Qn-i)*2.
Integrating again and noting that when
x—°i y—y^— 1» there results
EI(y — 2/n-i— tan./?n_i«)=i(ai + «2 + . . . +
.an_i)2w«3 + \(clx + a9-j |- «n_i) w«3 + ^w*c4
-4KQ. + «t(Q. + Qi)+«,(Qo + QO+Q9)
E^=| (ax + «„ + .... + <arn-i) V + ^ + a,
+ . . . . + an_1(Q0 + Qi+Q2+ +
Qn-s)F-KQo + Q^ • • • • *Qn-lK.
The integral equation of the elastic line
between An_i -and An in the last two
equations, making #=an, y=yn, and
tan. fin, they become
EI(tan./?u— tan.^n-iJzzii^ + ^-f
4-«n-l)^6/n + -J («,+«„ + .... +«n-l)
w a\ + ±wa\ — KQ, +a2 (Q0 + Qx) + a3
(Q. + Qx + Qa)+ • • • • +«n-i(Q0 + Q1 + Q5
+ . . . +Qn-2)]«n— J(Qo + Qi+ • • • +
Qu_i)a2n . The last one becomes EI
^J^_tan./fe_i[=i(ai.+ aJ+ . . .
+ an_i) Wn -|- %{a\ + es2 4- . . . + fln_i)wa2n
+ -gV *0«3n - | [>i Q0 + a9 (Q0 + Qi) + az
(Q. + Q, + Q,) + +an-i(Q. + Qi+.
Q2+ .. .. +Qn-2K-|(Q0 + Qi + Q2 +
. . . . +Qu-l)«2n.
These equations taken in conjunction
with the two general equations of equili-
brium given below are sufficient to solve
the problem, (al + a2 + a3 + .... )w=Q0
4-Q, + Q2+ ... and «1Qn + «2(Q0 + Q1) +
«3(Q0 + Qx + Q2)+ =4(«x + tf2 + a3 +
)2w, being the general equations.
The eqs. deduced are true for all indices
w=l, 2, 3, &c. This method of treat-
ment is the one given by Schemer; it
first becomes applicable when the num-
ber of spans exceeds three. The number
of equations for any example may be
reduced one half when the conditions on
each side of the center of the girder are
identical. If the points of support and
isolated loaded points are in the same
horizontal line yn> yn-i, &G-> disappear.
The method of using and determining
the Clapeyronian numbers will now be
given. These numbers play an import-
ant part in the solution of continuous
girders. Let the number of moments be
(n-\- 1), the moments at the two abut-
ments M and Mn+i equal zero. The
equations involve these moments and
constants, depending upon the length of
the spans, intensity and distribution of
the loading, they will be of the type
aiM2 + 6i.M3=Ai
aJVI2 + 62M3 + d2M4=A2
a3M3 + 53M4 + ^M5=A3
an_i Mn_i 4- £n_i Mn = An_i.
560
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Multiplying the first by c8, the second
by c3 and so on, we will get,
a,c,Ma + £2c3M3 + tf2c3M4=c3A2
«3c4M3 + 63c4M4 + d3c4M5=c4 A3
an_i cn Mn_i + bn-i cn Mn = cn An_i
Adding these equations we get
(aic„ + aac3)M3 + (6ica + 62c3 + «3c4) M3 + (<£a
es + *sc« + . . .)M4 + +(...+
&n-i cn)Mn=A1c2 + A2c3+ + cu An_!
This equation involves all the moments
with only known and arbitrary con-
stants. These are arbitrary constants;:
c2, c3, c4 &c, which are the Clapeyronian
numbers, may be so chosen as to make
the coefficients of all the moments disap-
pear except one,
known. In the same
moments may be obtained. By placing
the coefficients of the moments we wish
to disappear equal to zero/ the relation
between the Clapeyronian numbers is-
easily seen.
which will then be
way the other
ON A NEW DYNAMOMETER FOR LOCOMOTIVES.
By H. KILLICHES.
From " Die Eisenbahn," Abstracts published by the Institution of Civil Engineers.
This dynamometer is intended to an-
swer the same purpose for locomotives as
the friction brake dynamometer for or-
dinary engines. The instrument is fixed
between the engine and the first carriage
and records, by means of a 'pointer mov-
ing over a face like that of a gas meter,
the number of hectometer-tonnes per-
formed by the engine in any given time.
For this purpose the revolutions of one
pair of wheels are measured by means of
a worm fixed on the axle, engaging with
a small worm wheel which is mounted
on a long spindle reaching from the axle
to the recording apparatus between the
engine and the carriage. Here the
motion is transferred, by means of a pair
of bevel wheels, to another small shaft,
which carries a large disk. Against the
face of this disk presses a small wheel,
connected with a spiral spring, which
through a system of levers, is extended
by and in proportion to the strain on
the draw-bar. When this strain is zero,
the wheels rest exactly on the center of
the disk; but when the strain has any
other value, the wheel is pushed out-
ward towards the circumference of the
disk through a proportionate distance and
it then revolves by friction with the same
velocity as the portion of the disk at
that particular distance from the center.
Thus, it will be seen that when the speed
of the axle is constant, the revolutions
of the small wheel are proportional to
the pull on the draw-bar, and when the
pull is constant; the revolutions of
the small wheel are proportional to
the speed of the axle or to the dis-
tance run by the train; therefore,
when both vary, the revolutions of
the small wheel are proportional to
the product of these two (the pull on the
drawbar and the distance run by the
train), i. e., in other words, to the work
done by the engine. All that remains
is to connect this wheel to the pointer
by a train of clock-work, and the latter
will then record the work done. Vari-
ous devices and precautious are described
for rendering the principle efficient, "and
an account is given of experiments
made with the apparatus on the Arch-
duke Albert railway, in Austria. It was
found, for instance, that the greatest va-
riations in the resistance to tractionrtook
place in April and May, on account of
the changeable weather; and, again, that
the traction was less towards evening,
because the weather is then generally
finer, and there is less wind. The appa-
ratus applied, either to ascertain the
average work done during a long trip, or
the total work at some special part of
the line. In the latter case, the record
must be noted at short intervals, and the
speed observed independently. The fol-
lowing important points, among others,
may be determined by the use of this
dynamometer :
THE USE OF ZINC IN STEAM BOILEES.
561
1. The actual power of an engine, and
the proportional consumption of fuel
may now, for the first time, be accurately
ascertained.
2. The tables of maximum load on in-
clines, &c, may be corrected and veri-
fied. The maximum loads should be va-
ried according to the season of the year,
by an amount which will be fixed by the
use of the dynamometer.
3. In cases where trains are delayed,
&c, the dynamometer will show whether
this was due to an increase in the tract-
ive force or to the fault of those in
charge of the train.
4. It enables the amount of fuel con-
sumed, in proportion to the work done,
to be accurately known, and the prizes
for economy given to the drivers to be
placed on a rational basis. It must, of
course be remembered that it does not
give the work done in moving the engine
itself, but this can be easily ascertained
by other means, and is not subject to
much variation from differences of wind
and weather.
THE USE OF ZINC IN STEAM BOILERS.
From "Engineering."
The employment of zinc in steam
boilers, like that of soda, has been adopt-
ed for two distinct objects, (1) to prevent
corrosion, and (2) to prevent and remove
incrustation. To attain the first object
it has been used chiefly in marine boilers,
and for the second chiefly in boilers fed
with fresh water. We purpose dealing
with each head separately in the above
order, and in as popular a manner as the
subject will allow.
The suggestion to use zinc for the pro-
tection Of the copper sheathing of ves-
sels by Sir H. Davy, and his develop-
ment of this principle in 1824, appears
to have suggested to Professor E. Davy,
about ten years later, the application of
zinc for the protection of the iron buoys
in Kingstown Harbor. This is probably
the first application of the principle to
protect iron against the corrosive agency
in sea-water. The application of the
same principle to protect the interior of
steam boilers against corrosion does not
appear to have been attempted before
the year 1850. It was not, however, till
the introduction of surface condensation
for marine engines that zinc can be said
to have been extensively used to prevent
the corrosion of the iron plates and tubes,
which were no longer protected to the
same extent by the scale that formed
upon them when jet condensers were
used.
Zinc has been applied in various ways
in marine boilers, viz., by suspending it
in plates of various size and number
Vol. XIX.— No. 6—36
from the stays, and more rarely amongst
the tubes where practicable. The zinc
plates or bars have been placed in boxes
in various parts of the boiler, sometimes
for the feed to pass through, and in
other cases the zinc has been arranged
for the feed to deliver upon it as it
enters the boiler. As may be imagined,
these various ways of applying the zinc
led to very different results. In a great
many cases its use was not attended with
any apparent advantage, and it was con-
sequently discontinued. In other cases,
however, where its application had been
made in a more judicious manner, it was
more successful, and its use has been con-
tinued with very favorable results up to
the present time.
It is evident, from the manner in which
zinc has been employed in the great
majority of cases to prevent corrosion,
that the principle of its action has been
assumed to be simply chemical; that it
had a greater affinity than the iron for
the oxygen and acids in the water. In
order that this supposed simple chemical
action should take place efficiently, and
that the corrosive agents throughout the
whole body of water should be neutral-
ized, it would be necessary that they
should all be brought in contact with the
zinc before they could come in contact
with the plates and tubes. Were the
zinc soluble in water, this condition
might be carried out, but as zinc is not
soluble, and cannot reach all the corro-
sive ingredients in solution, or held in
562
VAN NOSTRAND'S ENGINEERING MAGAZINE.
suspension and diffused throughout the
water, it follows that all the particles of
water must be brought and kept in con-
tact with the zinc for a time in order
that it may be really efficacious. That
this is likely to take place in a large
boiler with a few pieces of zinc cannot
be maintained. Were the simple chemi-
cal action alone relied upon for the pro-
tective action of the zinc, the plates and
tubes should be nearly covered with it in
order that this action should be effective,
since the iron would share with the zinc
the corrosive action of the water, in pro-
portion to the surface of each metal ex-
posed. We must then look for some
other explanation of the success which
has attended the introduction of a few
bars of zinc into a large boiler.
The remarkable protection that zinc
has afforded in many authenticated
cases, can only be explained by ascrib-
ing it to galvanic action. When a metal
like iron, which is acted upon more or
less by a liquid, is brought into contact
with another metal like zinc, which has a
much stronger affinity for the oxygen of
the liquid, or for the acids of the salts
contained in solution, the zinc or
positive electrode is dissolved and im-
parts a negative tendency to the iron,
which preserves it by preventing the
oxygen or acids from acting upon it.
In most cases where zinc is employed
with advantage to prevent corrosion in
boilers, the water is a weak solution of
salts. This solution is decomposed by
the galvanic current in such a manner
that the oxygen and acids are liberated
at the positive pole ( + zinc), and the
hydrogen of the water and metal of the
salt at the negative pole (—iron). The
decomposition of the water, or electroly-
sis as it is called, takes place in such a
manner that the oxygen of one molecule
of water in contact with the zinc is sepa-
rated, and the liberated hydrogen com-
bines with the oxygen of a neighboring
molecule, whose oxygen in its turn
combines with the hydrogen of the next
molecule, and so the action goes on till
the hydrogen of the water in contact
with the iron at a considerable distance is
liberated, without the hydrogen and
oxygen having to cross the water as free
gases. It is in consequence of this action
that a piece of zinc placed in the middle
of a plate of iron has the valuable prop-
erty of exercising a protective influence
over a large surface of which it is the
center. The extent of the range of its
action will depend .upon the purity of
the zinc, the nature of the salts in solu-
tion, the temperature of the water, and
the condition of the surfaces of the zinc
and iron. In order that the protective
action may take place effectively, it is
necessary that the zinc and iron should
be in perfect metallic contact. It is
extremely probable that the fulfillment
or not of this last condition has deter-
mined the efficacy or non-efficacy of the
application of zinc in the numerous cases
where it has been tried with such differ-
ent degrees of success. Zinc " bottoms "
should not be used, nor indeed is some of
the spelter in the market sufficiently pure
to act to the best advantage. But, as a
rule, good commercial English or Belgian
zinc may be considered as l^eing sufficient
for the purpose. A high temperature is
favorable for the setting up of the gal-
vanic current, and therefore for the pro-
tection afforded by the zinc.
Besides having the zinc and iron in
perfect metallic contact, it is necessary
for the maintenance of the galvanic cur-
rent, upon which the success of the ap-
plication of the zinc depends, that the
surface of the zinc exposed to the water
should be kept clean and free from any
non-conducting coating that may be .
formed by the chemical action that en-
sues on the liberation of the oxygen and
acids at the surface of the zinc. This
brings us to a very important considera-
tion that is liable to be overlooked.
When the oxygen and acids are set
free at the surface of the zinc, oxide of
zinc is formed, and this combines with
the acids to form salts. These salts are
either soluble or insoluble in the water.
If soluble they become diffused through
the water, the zinc is kept clean, and the
galvanic action is sustained at the ex-
pense of the zinc. If insoluble the salts
tend to collect upon the zinc, which in
time becomes coated with them. As
this coating is a non-conductor, the gal-
vanic action is gradually arrested, and,
in time, ceases altogether, the presence
of the zinc being consequently no longer
efficacious.
With sea-water the sulphuric and
hydrochloric acids liberated from the
contained sulphates and chlorides, com-
REPORTS OF ENGINEERING SOCIETIES.
Trine with the oxide of zinc, and from
sulphate and chloride of zinc, which are
very soluble, hence the successful appli-
cation of zinc in marine boilers. But in
boilers fed with fresh water where the
acids liberated are too small in quantity
to combine with all the oxide of zinc to
form soluble salts, the film of oxide that
forms on the surface of the zinc, in time,
puts an end to its useful effect.
It is well known that the galvanic cur-
rent has no effect on the oxygen in solu-
tion in the water, and that it is only the
oxygen chemically combined with the
hydrogen in the water, and in the bases
of the salts, that are liberated at the
surface of the zinc. The question then
arises, how can the zinc protect the iron
from the oxygen in solution in the water
which may be in contact with the plates ?
The answer is, by a secondary and chem-
ical process, viz., the hydrogen liberated
at the surface of the iron combines with
the oxygen in solution and forms water,
or the metals liberated from the salts at
the surface of the iron unite with this
free oxygen and form bases. In fact
these metals have such an affinity for
oxygen that they attract it from the
water and residuary hydrogen is evolved.
We have been led to this length in ex-
plaining the principles upon which the
success or non-success of zinc depends, as
it is likely to be largely employed since
the Admiralty Boiler Committee have
spoken so strongly in favor of the use of
zinc for preventing corrosion. The por-
tions of the Boiler Committee's report
treating of the use of zinc, are very
valuable, and we shall deal with them in
a future article, when we shall also have
something to say on the use of zinc for
preventing incrustation.
REPORTS OF ENGINEERING SOCIETIES.
American Society of Civil Engineers. —
At the recent annual meeting the fol-
lowing persons were elected officers of the
American Society of Civil Engineers for the
year beginning November 6th, 1878: President
— W. Milnor Roberts; Vice-Presidents — Albert
Fink, James B. Francis ; Secretary — John
Bogart; Treasurer — J. J. R. Croes; Directoi's —
George S. Greene, William H. Paine, C. Van-
dervoort Smith, T. C. Clarke, Theo. G. Ellis.
Engineers' Club op Philadelphia. — At
the last meeting of the Club, Professor
Lewis M. Haupt, President, read a paper on
"The Scales of Maps and Drawings," giving
some simple rules for the removing of ambi-
guities at present existing. It is evidently
incorrect to indicate the scale of a map as so
many inches to the mile, or of a drawing, as so
many feet to the inch, when the intention is a
certain number of miles or feet to the inch of
paper. The paper also referred to the great
number of scales in use, and the great incon-
venience caused thereby, urged the necessity
for some measures which should reduce or
overcome this defect, and closed by presenting
two tables of map equivalents, showing the
number of miles, kilometers, chains, poles,
meters, yards and feet which are equal to one
inch of map, for any scale, and reciprocally
the number of square inches of map required
to represent one or more units of the above
denominations.
Mr. I. W. Morris read a letter from Mr.
' C. F. Conrad, which gave the following in-
I teresting information in regard to the " Butler
Mine Fire Cut-off:"
"Before locating the line of the cutoff, I
learned of the first fire which they had in the
same vein (14 feet thick) in 1856-57, and after
careful inquiry learned its position and made
my location for the through cut to pass as near
; as possible through the center of the "old fire."
i This was done, hoping to find all combustible
! matter, coal, "gob" and carbonaceous slate
I burnt to ashes, in which case it would have
I saved many thousand yards of excavation, as it
I would have presented an impassable barrier to
! the progress of the present fire.
This cut- off afforded an opportunity rarely,
i if ever, equalled to learn truly and fully the
| work of a fire in a coal mine. It was found
the slate above and surrounding the coal and
all the " gobb " was burned either to ashes or
i into slag, resembling ordinary furnace slag,
! while the pillars of solid coal were perfectly
1 sound and bright. About the middle of the
1 14-feet vein of coal is an 8-inch line of slate,
j and this was found burned to a white ash,'
j while the coal above and below were perfectly
| bright. When the fire reached the end of the
j workings it made no further progress, but,
I after burning the fallen rock to ashes or slag, it
I entered the face of the coal two or three inches
i and then went out.
Mr. Conrad concludes by saying that he is
! led to believe that solid coal cannot be burnt in
; place; that slate rock found in coal veins con-
! tains more gas than the coal ; that fires in coal
i mines are fed and live on the "gob "(refuse
j slate, &c), and gases, and that "gob" is an
! excellent reservoir for gas. Ventilation will
carry off free gas, but "gob" holds gas as a
sponge does water.
Mr. Edward R. Andrews, of Boston, proprie-
tor of the Hayford Creosote Wood Preserving
Works, gave a full description of the apparatus
employed in his process and of the results
obtained by the use of creosoted wood. Decay
in wood is due primarily to the fermentation
of the albumen of the sap, which commences
as soon as the necessary conditions, heat and
moisture, are supplied. The aim of all wood
preservatives has been to overcome this
fermentation by coagulating the albumen.
Experiments to produce this result were made
as early as 1700.
564
VAN NO STRAND'S ENGINEERING MAGAZINE.
Bethel, 1837, introduced dead oils as wood
preservatives, and to show the success which
has attended this process, it is only necessary
to state that it is used by every railway in
England, where nearly all timbers used In
construction are impregnated with creosote.
The Hayford process differs from that of
Bethel in this particular; the latter can only
be applied to seasoned timber, while in the
former process timber can be taken as it comes
from the saw mill and creosoted in a few
hours.
The cost of creosoting railroad ties is from
25 to 30 cents per tie. Paving blocks have
recently been treated for the Broadway
Bridge, Boston at a cost of $12 per thousand
feet, cord measure.
A section of a railroad tie was shown which
had been in use in Scotland for over twenty
years, and seemed to be in perfect condition;
the rail has not cut it, and there are no signs of
rot in the spike holes. There is every reason
for believing that creosoted ties will last here
for twenty years as well as in Europe Already
several railroads are using them. In 1875 the
Central Kailroad of New Jersey laid ten
thousand creosoted ties near Bound Brook,
which, thus far, show no signs of decay.
In addition to protecting from decay, creo-
soting is equally a specific against destruction
of wood by marine worms. Experiments are
being tried on ship timber in the U. S. steamer
Vandalia, now in the Mediterranean. This
vessel was built at the navy yard in Charleston
during 1872. All the timber except ihe live
oak ribs, both inside and out, were creosoted
by the Hayford process. The vessel went to
sea in 1874, and is expected home next year,
when the result of the experiment will be
known.
When we take into consideration the enor-
mous drain which is being made on our supply
of timber, stripping the forests altogether from
many parts of our country, it would seem that
we ought to be alive to the importance of pre-
serving timber.
Mr. Percival Roberts, Jr., read a very able
paper on the " Strength of wrought iron in
structures." He called attention to the great
need for more accurate knowledge in regard to
the strength of wrought iron, and criticised, in
a terse and interesting manner, some of the
testing machines and specifications of the
present da3r.
IRON AND STEEL NOTES-
In speaking of the Birmingham wire gauge,
the warden of the Standards in his last re-
port says that there is no standard wire gauge,
or common agreement amongst those interested
as to what are the dimensions in parts of an
inch of the several slots or sizes of the true
B.W.G. Its sizes are not geometrically or
arithmetically progressive, and consequently
bear no definite relation to each other. Its
origin is obscure, and it would appear that the
several slots or sizes arose from time to time
as a new wire or a new plate was introduced,
and as the exigencies of a particular trade de-
manded. In Germany, gauges for wire or
sheet iron have not yet been officially controlled*
The Birmingham gauge, commonly called the
" English gauge," is mostly in use in Northern:
Germany for measuring sheet iron, wire, and
hoop iron. In Southern Germany, the B.W.G.
is also used, and for the measurement of wires
the French gauge, which is a progressive scale
of tenths of a millimeter (1 millimeter—
0.0393709 inch) is also used. For sheet iron
the "Dillingen gauge," which is a scale of
Paris lines (1 line=0. 08881377 inch) is also used
in Southern Germany. The wire factories in
Westphalia use a particular gauge called the
"Bergish, or Westphalian." For sometime
past the question of establishing a uniform
wire gauge and a uniform numbering of wires
has been energetically agitated in Germany.
The manufacturers in Russia use different
gauges of English, German and French pat-
terns. In Canada only one gauge is known to
mechanics — the Birmingham wire gauge —
made by Stubbs, of Warrington. In France
measurements are made by the scale of one-
tenth of a millimeter as well as by the Bir-
mingham and Dillingen arbitrary guages. In
America the B.W.G. is extensively used, but a
special committee recently recommended the
expression sizes in thousandths of an inch, or
in fractions of a millimeter. An international
standard gauge is much wanted. Meanwhile,
it should be remembered that in anv contract,
bargain, sale, or dealing, the sizes of wire and
metal plates are legally expressed only in Im-
perial measures or in parts of an inch.
DIFFERENT QUALITIES OF IRON AND STEEL. —
By C. Grauhan. — The Author describes
at full length the characteristics of the different
species of steel and iron. Of steels he men-
tions puddled, Bessemer, Martin, and cast
steel, pointing out that generally the first has
the coarsest and the last the finest grain; pud-
dled steel generally shows some traces of
having been formed of several pieces, while
Bessemer and the other qualities, being cast in
blocks, are homogeneous. But Bessemer
metal is frequently porous, and when worked
up for railway axles or similar purposes, the
bubbles are first closed by forging, but show
themselves again in the form of longitudinal
cracks when taken out of the lathe. These
bubbles occur seldom in Martin steel, never in
cast steel. And a further difference between
Martin and Bessemer steel is, that the former
contains less silica.
According to the Author, the quality of steel
cannot be fairly tested unless it is first harden-
ed, as otherwise a bar which was rolled rather
hotter than another would show quite a differ-
ent texture, although of the same metal. The
steel should be heated, forged to bars of a uni-
form size, and then hardened in water, which
process eliminates any chance differences. If
a bar thus prepared be broken, the texture,
color, and general appearance of the fracture
will give a very close approximation to the
quality. Of course, although fine-grained
steel is better than coarse grained, the former
cannot be used for every purpose. Rails and
axles, for instance, require coarsegrained,
porous, and soft metal. If after sudden im-
KAILWAY N"OTES.
565
mersion in water the grain is as coarse as be-
fore, the steel is not fit for hardening and ap-
proximates to wrought iroD. The finer the
grain the harder is the metal and the more car-
bon does it contain. If the fracture shows a
coarse grain and a whitish reflection there is a
good deal of phosphorus and silica in the steel,
which is, of course, injurious. If it shines
blue instead of white the metal is burnt and
contains too little carbon.
As a rule, the hardness of steel depends on
the amount of carbon it contains, and the
quantity of carbon resulting from analysis is
used as a measure of its hardness.
Herr Grauhan mentions the different methods
of testing iron, of which he prefers the chemi-
cal mode, and gives the following results of the
analyses of various sorts of iron :
1. WESTPHALIAN BESSEMER IRON.
Per cent.
Iron 86.912
Carbon 3.200
Silicium...- 3.140
Manganese 6.180
Phosphorus 0.120
Sulphur 0.070
Copper 0.380
2. WELSH IRON (WHITE).
Iron 94.400
Carbon 2.400
Silicium 0.800
Sulphur 0 . 700
Phosphorus 1 . 500
Manganese 0 . 200
3. SPIEGEL IRON FROM MUSEST.
Iron 82.860
Carbon 4.323
Silicium 0.997
Manganese 10. 707
Phosphorus 0 . 059
Sulphur 0.014
Copper 0.066
4. BESSEMER RAIL FROM A WESTPHALIAN
WORKS, WHICH BROKE IN UNLOADING.
Carbon 0.370
Manganese 0 . 650
Silicium 0.223
Sulphur 0.040
Phosphorus 0.084
5. [ CAST-STEEL AXLE FROM A WESTPHALIAN
WORKS.
Carbon 0.221
Silicium 0 . 061
Phosphorus 0 . 052
Sulphur 0.072
Manganese 0 . 276
Copper 0.072
8. RETORT-STEEL TIRE OF A WESTPHALIAN
WORKS.
Carbon 0.5800
Sulphur 0.0380
Silicium 0.1010
Phosphorus 0.0407
Manganese 0.6080
N.B. — The tenacity of this tire was 71 to 74
kilogrammes per millimeter, or about 43 tons
to the square inch. — Abstracts of Institution of
Civil Engineers.
/Chromium augments the hardness and tensile
\J resistance of iron alloys; but it has no
" s'teelifying " properties, and cannot take the
place of carbon. Boussingault fused chromic
oxide with cast iron in such proportions as to
burn all the carbon of the latter with the
oxygen of the former; but the non-carbonifer-
ous alloy of iron and chromium thus obtained
would not temper. Berthier is the real dis-
coverer of the acier chrome, or chromised
j steel. As long ago as 1821, he indicated the
I means of introducing chromium into cast steel,
i and announced that the compound thus formed
! possessed properties which might render it
I precious for many purposes. It is now manu-
I factured, says M. Holland in his "Note sur
I F Acier Chrome," just published in Paris; at
| Brooklyn, N.Y.; Sheffield, England; and in
j France at Unieux, in the department of the
I Loire. A sample of ferro-chrome from Brook-
lyn, analysed by Boussingault, showed 4.29
I per cent, of combined carbon and 48.70 of
chromium. The ferro-chrome of Unieux con-
j tains about 5.4 per cent, of combined carbon
j and up to 67.2 per cent, of chromium. Chrome
I steel is made at Unieux, as at Brooklyn, by
j fusing in crucibles, in a Siemens furnace,
fragments of wrought iron or steel of the first
i quality, with an addition of ferro-chrome cal-
: culated for the degree of acieration and hard-
i ness required. The steels of Unieux vary in
i their contents of chromium from 0.5 to 0.9 per
cent. Boussingault found in a hard steel from
i Brooklyn 1.1 per cent, of combined carbon and
0.44 of chromium. Concerning the properties
of chrome steel, and the peculiar manipulation
required in working and tempering it, M. Rol-
land gives substantially the same statements as
the circulars of the Chrome Steel Company, of
Brooklyn. The directions ma}' be summed up
in two : For working — except punching, which
may be done, it is said, at a moderate tempera-
ture— the heat should be high — nearly white at
first; for tempering and hardening, a low
cherry heat is the best. M. Rolland says, in
conclusion, that chrome steel is as yet but little
known, and much restricted in its applications.
M
RAILWAY NOTES.
R. A. C. Franklin, of Brighton, is bringing
out a tram-car motor in which a central
wheel is used for propulsion on the common
road, no reliance being placed upon the ad-
hesion of the wheels upon the rails. Com-
pressed air is to be employed in long cylinders,
in which pistons reciprocate and work racks
geared upon pinions upon the driving wheel
j axle, arrangements being made for producing
j revolution in one or both directions, whichever
| way the pistons are moving. Some practical
trials will probably be made.
The employment of wheels larger than those
commonly used on American stock has
lately occupied much attention. A trial having
been made of the value of 33 inch and 42 inch
| car wheels upon long-distance express trains,
l the Boston and Albany Railway is preparing
{ to place the larger size under all its New York
I through passenger cars. The life of the usual
TAN NOSTRAND'S ENGINEERING MAGAZINE.
cast iron 33 inch wheel on these long running
trains is about four years, but of late the steel-
tired wheel has been run a very much longer
time. The new wheels will be of the steel- tire
pattern, and made by a Hartford, Conn., com-
pany, and the change in all its incidentals will
involve an outlay of over £5000. The superin-
tendent expects to secure not only a stronger
wheel but one less liable to catch at the joints
and pound the rail ends, much less friction in
the journals, and less danger from hot boxes.
6 * fPo whom are we indebted for the Railway
1 Ticket System," is the title of a small
pamphlet, in which Mr. J. B. Edmonson gives
an account of the origin, invention, and rise of
the railway ticket system, as now adopted by
almost every railway company throughout the
world. The invention and system are due to
the labors of one Thomas Edmonson, who was
born in 1792, became connected with railways
in 1844, and seeing the disadvantage connected
with the paper voucher written arid supplied to
passengers, contrived a rude method of print-
ing cards, arrangements for numbering them,
and cases in which the tickets thus made could
be arranged and kept for issue. The printing
apparatus was at first very crude, but the
arrangement of the ticket cases and tubes are
now very much the same as when Edmonson
contrived them. He subsequently designed
very complete machinery for printing, number-
ing, and checking the numbers of the tickets,
and designed arrangements of color and
number for purposes of checking the receipts.
The pamphlet is published by H. Blacklock &
Co., Manchester.
Some interesting information is conveyed by
the recent report of the Board of Trade on
the railways of the United Kingdom during
1877. These reports are not usually very
attractive reading, but having overcome one's
mental inertia, we are enabled to learn from
them something that is not the less useful
because it is somewhat discomforting. With
all our railway improvements, our working
expenses grow rather than decrease, though a
few lines must be excepted. Thus in 1870 the
maintenance of way cost 5.89d. per train mile,
in 1877 this was increased by 1.63d., locomotive
power costl.07d. more, traffic expenses 2.24d.,
and other items 0.86d. more. The ratio of
expenditure to traffic receipts, though rather
less than in 1876, was 54.1 per cent. For the
last five years the proportions have been : 1873,
54 per cent,; 1874, 55.6 per cent.; 1875, 54.6
per cent.; 1876, 54.2 per cent. 4 and 1877, 54.1
per cent. In 1870 it was but 48.8 per cent.
Now as the difference of a penn}^ per train
mile amounts to about a million sterling, and
of 1 per cent, in the proportion of expenditure
to receipts,to about £600,000, there would be-
an enormous addition to the net earnings of the
comganies if they could get back to anything
like the workmg'expenses of 1870.
Railways are in course of construction in
Russia in Asia, Contractors' trains are
now, it is said, running over the Ural Moun-
tains to the city of Ekaterinereburg, just on
the Asiatic side. This place is in about lati-
tude 57 and in longitude 60 deg. east of Green-
wich, that is, about 100 miles further north and
800 miles further east than Moscow — as far
north as Aberdeen and as far east as the head
of the Indian Ocean. There is now on the
Eastern Continent a continuous line of railroad
from longitude 10 west to 60 degrees east of
Greenwich, the western terminus being south
of latitude 40, and the eastern about latitude
57. This exceeds the extent of the North
American system from about 46 west of Green-
wich— Halifax — to 105 west — San Francisco^
The European system covers 70, the North
American 59 degrees of longitude. The rail-
road enters Ekaterinereburg from Perm, which
is about 190 miles north-west, by a high level
line, and in that inland and elevated district
must have a very severe winter. It is not
quite so far north as St. Petersburg and the
Finland railroads, but the latter have the
winters somewhat modified by the nearness of
the Baltic Sea; while Perm has no sea nearer
than 800 miles, and that is the arctic, and the
Ural range is close by. The road from Perm
to Ekaterinereburg, 3*10 miles, was to be opened
to the public September 1st, and a good deal of
work has been done on an extension of the
road into Siberia.
The final result of English railway working
in 1877 may be stated as follows: The
extent of the system increased 1.2 per cent.,
the double mileage 0.7 per cent. The capital
increased 2.4 per cent., and the capital per
mile open increased 1.2 per cent. The ordinary
capital increased more slowly than the total
capital, or only 1 . 2 per cent. The gross receipts
increased 1.2 percent., or rather less than the
rate of increase of capital; but the working
expenditure increased only 1.0 per cent, so
that the increase of net earnings is 1.5 per cent.
The receipts, expenditure, and net earnings per
train mile have all decreased slightly. The
result is (1) a slight diminution of the percent-
age of net earnings on the whole capital, viz.,
from 4.36 to 4.32 per cent,, and (2) a slight
diminution of the dividend paid on the ordinary
capital, viz., from 4.52 to 4.51 per cent, These
are the results in a year in which the increase of
traffic was at a lower rate than at any time since
1858, the average rate having been in that period
4.65 per cent,., while last year it was only 1.21
per cent. They are also the results at a time
when the rate of working expenses is at a high,
level compared with the whole period prior to
1872. The result to railway capitalists cannot
be deemed unfavorable, though the average is
composed in part of some unfavorable
extremes. As regards the public use of rail-
ways, the increase of third- class traffic, as well
as of minerals and goods conveyed, would
appear to show that that use has been increased
in 1877 in a greater degree than the return to
the owners of the railway system.— Engineer.
The use of chilled cast iron wheels is, accord-
ing to a correspondent of the American
Railroad Gazette, slowly but steadily getting
into favor in Europe, especially on the Austro-
Hungarian railroads, which have for many
years been using them with the best results.
In the year 1844, Mr. A. Ganz, a Swiss citizen,
established in Buda a foundry; and in 1854,
ENGINEERING STRUCTURES.
567
being induced by some railroad engineers, lie
began to experiment in chilling cast iron; and,
having on hand Hungarian ores of superior
quality, he was able, in 1857, to execute some
important orders for chilled wheels for the
Austrian and Hungarian railroads. The high-
est number of wheels produced by this estab-
lishment in a year was 36,000, in the year 1872;
but owing to the industrial crisis of 1873 it has
fallen off, and only during the last two years
has been increasing again, amounting now to
22,000 wheels a vear. In 1867, 100,000 had
been cast, 200,000" in 1871, 300,000 in 1874, and
400,000 will probably have been cast by the
beginning of next year. The wheels were
furnished to thirty different railroad compan-
ies. The manufacture of railway crossings
from the material is also an increasing industry.
The depth of the chill of the wheel tread is
from f inch to nearly f inch. Specimens of
wheel sections are exhibited in the Paris Exhi-
bition, and some old wheels, among which,
one No. 423, has run 128,987£ miles, and
another, No. 3684, has run 340, 446-^- miles, as
certified to by the Mohacs-Fiinfkirchen Rail-
road Company. They are both from under
cars in light service, and hardly show any
wear. Baron M. M. von Weber, in his report
to the Government (Vienna, May 31, 1874),
recommended diilled wheels for luggage
trucks, as being more economical and safe; he
states that there is but one-tenth as many
accidents from the breaking of chilled wheels
as from others.
The long talked of project of a railway across
the island of Newfoundland has been re-
vived by an Act of the Legislative Assembly
proposing to grant an annual subsidy of
£24,000 to any company which shall cod struct
and maintain a railway across the island, in
addition to granting liberal concessions of
Crown lands. The argument is that such a
road would not only open up immense deposits
of copper, iron, coal; nickel, lead and other
minerals, great pine and spruce forests, and
vast tracts of rich land, capable of producing
in abundance the finest quality of wheat, but
would virtually bring America almost a
thousand miles nearer Europe by making
practicable the establishment of a line of
steamers from St. John's, a point nearer to
Great Britain than New York by almost that
distance, while also avoiding the dangerous
part of the voyage between New York and
Cape Race. That a railway across Newfound-
land would .develope a large traffic is, says the
Railway Age, unquestionable; that it would
result in a considerable diversion of ocean
travel from New York to St. John's is some
what doubtful.
ENGINEERING STRUCTURES.
(^ost of Maintenance of Highways in and
J around Paris.— From a late number of
Annales des Ponts et Cbaussees we make the
following abstract of the report of M. Graeff,
Inspector General of Bridges and Roads.
The government appropriation for this de-
partment for 1878 having been fixed at three
million francs, M. Graeff calls attention to the
fact that as the total estimate called for
7,578,471 francs there would remain a requisi-
tion upon the city for upwards of four and a
half millions if the projected plans were exe-
cuted.
The estimates of cost of this and former
years show a gradual increase of cost of re-
pairing each of the three kinds of road surface
now in use : viz., pavement, asphalt and
broken stone.
The cost of maintaining paving was from
1872 to 1875, Of. 48 per square meter, in 1876 it
was Of. 51 and the estimate for 1878 is Of. 53.
For asphalt the cost from 1872 to 1875 was
l.f20 in 1876 l.f30 and estimated for 1878 at
l.f27 per square meter.
For broken stone (macadamized) roads from
j 1872 to 1875 the cost was If. 80 in 1876 it was
2f.ll and is estimated for 1878 at 2 francs per
square meter.
These figures show an advance in cost over
previous years, except for the year 1876 in
which the prices for asphalt and broken stone
were slightly above the current estimates. It ap-
pears that the advanced prices are due to in-
creased expense of both materials and labor.
The above estimates lead to the suggestion
that pavement bo substituted for the macada-
mized surfaces except in streets used mainly
by pleasure carriages, but it is added it does
not seem practicable to restrict the use of
broken stone any further at present. Economy
in this direction'is only to be accomplished by
securing the most durable road material.
In the meantime many of the streets need re-
pairing. They are in general only in fair con-
dition, and some are actually bad. It is esti-
mated that keep the thoroughfares in normal
condition -^ of their total surface should be
renewed, and it is to be regretted that the ap-
propriation for the current year will allow a
renewal of only ^ of their entire surface.
Wire Rope Conveyance. —By M. Korting. —
A system of aerial transit on suspended
wire ropes, designed by Messrs. Bleichert and
Otto, of Leipzig, has been established to con-
nect the gasworks at Hanover with the neigh-
boring 2oal station on the Hanover- Altenbeck
railway, for the supply of coal to the works.
The line crosses the Limmerstrasse and the
river lhme, and is about 625 yards in length.
There are two iron-wire ropes, placed 5 feet
10 inches apart, and employed respectively for
the carriage of loaded and of empty wagons.
They cross the Limmerstrasse at a height of
23* feet, and the river at about 30 feet. The
cables are respectively 1.12 inch and 1 inch in
diameter, and are constructed of wire of 4
millimeters, about ^ inch, in diameter. They
are supported on pulleys at intervals of 24
yards, except in crossing the river, on a span of
57 yards. Resting on pulleys, they are free
to expand or contract. They are kept taut by
weights of 5 tons and 4 tons respectively.
The wagons are drawn by means of a"T96 inch
endless wire rope, supported on rollers at in-
tervals of 60 yards, and driven by a six-horse
steam engine at a speed of three miles per
hour. The wagons are constructed of sheet-
568
VAN NOSTRAND'S ENGINEERING MAGAZINE.
iron, and are capable of holding three hecto-
liters, or 106 cubic feet of coal ; they are sus-
pended from the carrying ropes on two grooved
wheels, one in advance of the other, between
which the attachment of the wagon is made.
The bodies of the wagons are swivelled, so
that they may be easily emptied. They follow
each other at intervals of about 60 yards. Al-
lowing for delays, the quantity of coal carried
at no time exceeds 180 tons per day of ten
hours, and is frequently less, the average de-
livery being only 135 tons. The working
charges are :
£. s. d,
Seventeen men at 2s. 6d 2 2 6
One carpenter 0 3 5
Coal for the engine , 0 6 4
Oil, waste, &c 0 0 5
the increase in the traffic is not the main cause
of the increased wear of the roads. That the
more rapid wear has noticeably taken place
since the adoption of the steam rollers does not
offer any argument against the use of the latter,
inasmuch as the increase of traffic in the same
time has in more districts been remarkable.
There is reason, however, for believing that
the use of more finely broken road metalling
would, especially if mixed with a small quan-
tity of, say, Northamptonshire blast furnace
slag broken to a small size, when well rolled
and compacted under the steam road roller,
make a more durable road than is now made(
with large metalling and gravelly sand.
Per day £2 12 8
being at the rate of 4.67d per ton of coal con-
veyed. The total first cost of the system
amounted to £3,580, and the charge for inter-
est, depreciation, and 15 per cent, for mainten-
ance, is reckoned at 5.13d. per ton, making a
total charge of 9.8d. per ton, the former cost
being 1*. per ton.
Macadamized Roads. — Attention is being di-
rected to the condition and mode of con-
struction of macadamized roads in London.
It is stated, and there seems reason for the
statement, that the streets paved in this way de-
teriorate much more rapidly since the date of
the adoption of the steam road roller than they
did formerly. The reason for this is sought in
the difference in the size of the pieces of stone
now used and those used by M'Adam. M.'
Adam employed road material consisting of
pieces not larger than would pass through a
ring under 2 inches in diameter, but a large
proportion of those now used are not less than
double the weight of the pieces so measured.
The stone was formerly broken by hand, but
machinery does the work, so that the cost of
breaking should not be the explanation of the
increase in size, more especially as sand and
gravel is now employed during the rolling of
the newly laid metal for binding it together.
This binding, it is argued, is only required
in consequence of the increased size of metal-
ling, and that is soon washed away, leaving
the large stones loosened and easily removable.
Hence it is said that the roads are soon now in
holes because the metalling is too large. On
the other hand it is argued that, as the roads
are now pressed by the heavy steam roller in
place of the wheels of ordinary vehicles and
comparatively light rollers, larger stones are
admissible. It, however, remains to be learned
by roadmaking engineers who have the oppor-
tunity of observation, whether the roadway is
really as solid after the steam roller, as is
usually imagined, or whether the circular
rollers do not leave it in a condition somewhat
loose at least near the surface. It has also to
be learned whether the alteration in the size of
the metalling is attended with inferior results
and whether breaking the stone so small
originally is not simply helping the ultimate
disintegration. It has also to be proved that
ORDNANCE AND NAVAL.
Telescopic Artillery Sights. — We under-
stand that the French Government, being
satisfied with the preliminary trials with the
telescopic sights invented by Captain Scott,
RE., have purchased three instruments to
enable them to carry out exhaustive trials.
The object of his invention is: — (1) To enable
the gunner to take aim at distances equal to
the full range of the gun. (2) To dispense
with the errors of fire due to the inclination of
sights when the gun wheels are out of level.
(3) To enable the gunner to correct errors in
range and direction by infallible mechanical
adjustments, instead of calculations based
upon guesswork — good or bad according to the
experience of the firer.
The Expenditure op Ammunition. — The
Russian Invalide adds some facts to those
published in the Moscow Gazette, concerning
the expenditure of ammunition by the Rus-
sians. According to this account the Russian
artillery used 204,923 charges, and the infantry
and cavalry 10,057,764 cartridges, which are
distributed as follows: — Field Artillery — 1288
guns, 114,879 shells, 43,029 shrapnels, 1091
cases of grape shot; together, 158,999 charges,
or 123.46 per gun. Siege Artillery — 151 guns,
23,995 shells, 24,095 bombs, 4174 cases of grape
shot; together, 52,264 charges, or 346.12 per
gun. Small arms — 65,000 Berdan rifles;
3,625,364 cartridges, or 45.75 each; 37,000
cavalry carbines; 1,251,764 or 33.72 each;
217,000 Kruka rifles, 5,692,120 or 26.22 each;
16,000 revolvers, 88,516 cartridges or 5.42 each;
together, 335,000 small-arms of all descriptions,
which discharged 10,057,764 cartridges, or 30
each. According to the Russian Invalide, the
number of troops engaged in actual fighting
was 282,000 infantry, 37,000 cavalry, or 319,000
men, with 1288 field guns, making 3.9 guns to
1000 men. The large number of cartridges,
viz., 1,251,764 from 37,000 rifles, expended by
the cavalry, demonstrates the important part
played by the cavalry during marches, and in
its employment as infantry on fields of battle.
The Turks are reported to have lost, in Europe
and Asia, nearly 150,000 dead or wounded,
which would indicate that about sixty-seven
cartridges were required to place one man
hors de combat, taking no account of artillery.
The proportion of rifle firing to artillery fire
is as 49 to 1.
ORDNANCE AND NAVAL.
569
Pallisek on Projectiles. — Sir W. Palliser
has written a letter, suggested by the
artillery experiments which have recently been
carried out, in which he says that they up-
hold, to the satisfaction of all, the principles
advocated by him during the last fifteen years
in connection with iron plate penetration.
These are: — (1) That the form of the projectile
should be such that the pressure of the plate
should be brought to bear gradually on the
projectile: and (2), that the projectile should
be composed of a substance which offers a
great resistance to pressure. These principles
sound childlike in their simplicity; still they
were opposed to the received opinions of the
day. In advocacy of the principles the writer
says: "I applied them by making a pointed
(technically an ogival-headed) projectile of
common cast iron of a hard nature, which is
further hardened and compressed by casting
in a peculiar mold. The results of my inven-
tion were so great that the Government of the
day ordered that these projectiles should be
officially designated the 'Palliser Projectiles.'
All that now remains to me of them is their
name. I trust the writer of your article does
not wish to rob me of that too, for he makes
no allusion to it in connection with them. If
by any process it were possible to impart to
ogival-headed projectiles of steel, or of silver,
or of gold, the same property of resisting
pressure imparted to the cast iron in my pro-
jectiles, then a Palliser projectile of steel,
silver, or gold would be produced which
would, no doubt, give as good results as those
of cast iron. Experience has shown that it is
very difficult to impart this property with any
certainty into steel in large masses, and that its
existence caimot be proved excepting by trial
in the same manner as the Austrian soldier-
servant tried his master's lucifer matches and
found them all good, to the officer's great dis-
gust when he wished to light his candle in the
night. It is possible that similar difficulties
might be met with in the construction of silver
or gold projectiles. But why should public
money be wasted in this way when thoroughly
reliable projectiles cau be produced from cheap
cast iron which do all that can be required of
them — viz. , which will penetrate as far as the
gun has power to drive them ? Moreover, these
projectiles possess the valuable quality of sep-
arating themselves into many pieces in planes,
as a rule parallel with, and at right angles to,
the axis of the projectile." Notwithstanding
the progress in artillery since these principles
were first enunciated by Sir "W. Palliser, he
believes firmly in the superiority of his projec-
tiles for penetrating iron plates, and holds that,
provided his first principles be true, nothing
will ever be produced to surpass them.
BOOK NOTICES.
A Descriptive Treatise of Mathematical
Drawing Instruments. Fifth Edition.
By Wm. Ford Stanley. New York : E & F.
N. Spon. Price $2.00. For sale by D. Van
Nostrand.
A full description of all the implements em-
ployed by the draughtsman is certainly a use-
ful book. Four editions of the book are in
the hands of students in different parts of the
world.
Histoire Nationale de la Marine. Par
Jules Trousset. Paris : Libraire, M.
Dreyfous. Price $4.00. For sale by D. Van
Nostrand.
This voluminous history of the navies of
Europe is quite fully illustrated with portraits
and naval battle scenes. The pictures are
of medium quality only. The typography is
good enough and there is a good deal of it —
nearly 800 pages of large royal octavo size.
HANDBOOK OF MODERN CHEMISTRY, ORGANIC
and Inorganic By Dr. Meymott
Tidy. London : J. & A. Churchill. Price
$5.00. For sale by D Van Nostrand.
This large work is divided into three parts :
non-metallic elements, metallic elements, and
! organic bodies.
It may be regarded as a compend of chemical
I reactions and of the resulting compounds. It
I is not a book for a student, but will prove of
j good service to the working chemist or to the
I instructor.
It is well printed, contains 776 pages of mat-
ter, but no illustrations.
Experimental Researches in Pure, Ap
Hi plied and Physical Chemistry. By E.
Frankland, D.C.L. ; F.R.S. London: John
Van Voorst. For sale by D. Van Nostrand.
| Price $15.00.
The eminence of the author will insure a
j cordial reception for this work. A portion of
j this volume has already found a place in
i standard scientific works, having been publish-
j ed in the chemical journals in separate memoirs
during the past thirty years.
This book of 1030 pages presents the record
i of this author's labors down to the present
: time.
The typography, especially of the chemical
j formulas, is excellent.
i rPHE Artisan. By Robert Riddell. Phila-
i 1 delphia: Claxton, Remsen & Haffelfinger.
Price $5.00.
This is in an instruction book for the use of
I students. It is mainly a set of illustrative ex-
! amples beginning with practical geometrical
| problems and leading up to designs for timber
I constructions of various kinds. There are
| forty full page plates of quarto size, and a page
of text facing each plate.
Among other examples of a practical kind
we find : Finding bevel cuts for splayed work ;
Butt-joints for acute Angles ; Construction of
High-Root's ; Construction of Niches ; Platform
Stairs ; Hand-Railing, ets., etc.
The typography and plates are exceedingly
good.
PROCEEDINGS OF THE INSTITUTION OF ClVIL
Engineers. Excerpt Minutes. Edited by
James Forrest, A.I.C.E., Secretary.
We have received through the kindness of
Mr. Forrest the following papers of the Insti-
tution:
The Construction of Steam Boilers, adapted
for very High Pressures, by James Fortescue
Flannery.
570
van nostrand' s engineering magazine.
Portland Cement Concrete, by John Watt
Sandeman, M.I.C.E.
Portland Cement Concrete in Arches and
Portland Cement Mortar, by Charles Colson,
A.J.C.E.
A Skeleton Pontoon Bridge, by Bagot Wil-
liam Blood, M.J.C.E.
Annual Report upon the Survey op the
Northern and Northwestern Lakes,
and the Mississippi River. In charge of
Gen'l C. B. Comstock. Washington: Gov't
Printing Office.
This is an Appendix to the Report of the
Chief of Engineers for 1877. It contains four
folding plates representing the systems of trian-
gles about the great lakes, also four plates
exhibiting by curves the changes of water level
in the lakes separately.
Some detai]ed accounts of the measurements
of a base line and of astronomical work will be
especially interesting and instructive to stu-
dents of geodetic surveying.
The Physical System op the Universe —
An Outline of Physiography. By Syd-
ney B. J. Skertchly, F.G.S. London:
Daldy, Isbister & Co. For sale by D. Van
Nostrand. Price $c?.00.
The writer sums up in a careful way the evi-
dence bearing upon the theories of Geology
and Physical Geography.
The topics taken in order are, as presented
by the author in chapters, arc: I, Introduction;
II, Matter and Motion; III, Light; IV, The
Sidereal System; V, VI, and VII, The Solar
System; VIII, The Sun; IX, X, The Earth's
Internal Heat; XI, and XII, The Earth's
External Heat; XIII. Climate; XIV, Life;
XV, The Nebular Hypothesis.
Examples of Modern Steam, Air and Gas
JDi Engines. By John Bourne, C.E. Lon-
don: Longmans, Green & Dyer. For sale by
D. Van Nostrand. Price $30.00.
This work was begun some few years since
and issued in parts, each part being a quarto
with generally a folding plate and several large
wood cuts interspersed in the text. After a
long interruption to the publication, the final
parts have appeared, and the work as com-
pleted is a large quarto with fifty plates and
about 400 wood cuts.
The illustrations are so complete as to de-
tails that the explanatory text is scarcely
necessary. The plates are in most cases
" working drawings," and all moderm im-
provements are discussed.
Dictionnaire de Chimie. Pure et Appli-
quee. Par Ad. Wurtz. Paris: Li-
braire Hachette et Cie. For sale by D. Van
Nostrand.
This Dictionary is now complete. It in-
cludes Organic and Inorganic Chemistry; their
applications to manufactures, agriculture, and
the arts; also their bearing upon Physics,
Mineralogy and upon Physical and Chemical
research.
No pains have been spared to present topics
with a proper degree of fullness and pictorial
illustration.
References to the sources from whence the
articles have been condensed are given with
satisfactory completeness. •
In these days of rapid advance in Applied
Chemistry, such a compend of Chemical Pro-
cesses is to the Analyst or Manufacturing
Chemist indispensable.
Report on Bridging of the River Missis-
sippi between Saint Paul, Minn., and
St. Louis, Mo. — By Brevet Major General G.
K. Warren,— Major of Engineers. 232 pp.
8vo., with many maps. Washington, 1878.
For sale by D. Van Nostrand.
The report on bridging the Mississippi
River between St, Paul, Minn., and St. Louis
Mo., by Gen. G. K. Warren, is a very valuable
contribution upon the subject of bridging navi-
gable waters. Ordinarily, bridges have been
constructed for highways and railroads, onlv
in the interest of the companies building them,
and with little or no attention to the interests
of navigation. In all cases where there has
been a considerable amount of water traffic, it
is true that the companies have been compelled
to build draws, but these have often been very
badly situated and of difficult and dangerous
passing, and it was only when the navigation
interests of a great public highway like the
Mississippi became involved that sufficient in-
fluence was brought to bear upon the question
to protect the navigation from unnecessary ob-
struction by the bridges that must inevitably
be built. The matter was brought before
Congress, and General Warren was appointed
to make the necessary examinations, and re-
port. The interests involved in the construc-
tion of railway bridges over the Mississippi
and other large navigable channels are dia-
metrically in opposition. On the one side, the
railway companies desire to build bridges on
the grade of their road, in the best line for
them across the stream, and wish the most
economical spans ; and almost invariably pre-
fer a low structure with a draw, rather than
construct a high bridge under which steam-
boats can pass. On the other side, the river
traffic demands bridges at right-angles to the
current, with piers in its exact direction, wide
spans, and a superstructure which any boat
navigating the river can pass under at high
water. It was chiefly with a view to determine
how these conflicting interests could be recon-
ciled, that the investigations conducted by
General Warren were ordered by Congress.
The duty assigned to him has been admirably
performed. He appears to have impartially
considered the rights of all parties, and to
have brought a vast amount of keen observa-
tion and practical good sense to bear upon the
questions involved. He appears to have con-
sidered the subject in all its engineering, com-
mercial, financial and legal bearings, and to
have collected data and documents to support
his deductions, so that any one reading his re-
port can see the reasons upon which he bases
his conclusions.
Gen. Warren commences by stating the ori-
gin and nature of the investigation, and gives
a general description of the Mississippi valley
in connection with that of the Minnesota river.
He considers the geographical structure of the
BOOK NOTICES.
571
region embraced by the report, and advances
the hypothesis, previously more fully set forth
in his report upon the Minnesota River (Report
of Chief of Engineers, 1875) that the water
from Lake Winnipeg once flowed southward
into the Mississippi through the Minnesota
valley. There seems from his statements no
good reason to doubt the correctness of his
theory. He next gives a general presentation
of the requirements and advantages of western
river navigation, the necessity for wide spans
and high bridges, and a discussion of the data
for determining the headway required. He
then gives a description, with maps and dia-
grams showing the location and character of
the several bridges that have been constructed
between St. Louis and St. Paul ; likewise
showing the direction of the river current
through the openings between the piers. A
comparison of these in the different bridges is
very interesting. One of the bridges described,
the new bridge at Rockland, was designed and
located, as well as partially constructed under
his immediate direction. He then goes on to
give a general history of bridging the navigable
western rivers, in its relations to the laws, to
the decisions of the United States Courts, and
the debates in Congress. He also gives the
opinions of many eminent engineers with rela-
tion to the length of spans practicable and
other points of interest. He concludes with
an acccount of the manner in which his exam-
inations have been made. The whole report
shows the utmost attention to facts and details
of value for future reference, and represents
the immense amount of work performed by
General Warren and his assistants.
As an engineering essay upon the location
and general character of bridges .over large
navigable streams it is of great value to the
profession, both on account of the numerous
examples given with their advantages and de-
fects, and the plain statement of the principles
involved and which are as applicable to other
streams as to those described.
Graphical Statics. By A. Jay DuBois.
(A communication from the author.)
Dear Sir: — I notice in the November No.
of the Magazine a criticism upon the first
edition of my "Graphical Statics," translated
from the Zeitschrifl des Ver. Deuisch, Ing.
The extract is but a partial one, and it seems,
to me, at least, somewhat unjust that the few
surly and grudging words of commendation
which the author of the critique felt obliged
to give me for a work of great labor, evidently
much against his will, should have been
entirely omitted by your translator, and only
his animadversion given to the public.
With an honestly written and intended
criticism, whether complimentary or the re-
verse, I have not, however, and never shall
have, fault to find, and certainly shall not
take it upon me to answer. The same holds
good for the malicious attacks of personal
hostility. Witness: A criticism which ap-
peared in your own columns in February of
this year, the tone and tenor of which were so
personal and malicious that it was beneath
contempt, and formed its own best reply.
Small wonder that it went begging acceptance
of respectable journals until it finally found a
lodgment in your columns. If my work is
not its own best defense from such palpable
attacks, little that I could say, even were I
willing to say it, would have any effect.
When, however, a specific charge of dishon-
esty is made, I consider it my duty to meet it
squarely and brand it as slander.
The charge is as follows: "The American
reader is led to infer from DuBois' method of
reference that only one page of his Introduc-
tion is taken from Weyrauch ; when, in fact,
as I find after a thorough examination, there
are twenty-seven pages of close translation."
This I brand as a slander, and I wish to call
public attention to its entire lack of founda-
tion, and the source from whence it emanates.
I will do its author the justice to suppose that
it is unintentional and due more to ignorance
of the English language, or, perhaps, to natural
stupidity, rather than to real malevolence. If
not malevolent, however, it is certainly very
stupid and very conceited. If, instead of the
words "American reader," the critic had
spoken for himself alone, he would at least not
have been guilty of the conceit of supposing
the American reader as stupid as himself.
It is, at best, a very stupid error, and con-
sidering the gravity of the charge, an unpar-
donable one. No acknowledgment could
possibly be fuller than that which I have
made. I state in the Preface that I am in-
debted for the Introduction, with few altera-
tions, to Prof. Weyrauch, and I give the full
title of the brochure translated. That the
astute critic cannot find any alterations does
not prove their non-existence, but rather
illustrates still more forcibly his cast iron
"dumbness.'" Not content with this acknowl-
edgment in the Preface, which certainly covers
the Introduction sufficiently, I have, upon the
first page of the Introduction, refreshed the
memory of the reader by a foot-note again
referring to the original. This is the " method
of reference " which misleads, according to
our wiseacre, American readers !
Again, the "first page," which seems to
bother him so, closes as follows: "We have,
therefore, to ask of the reader who wishes to
obtain a just and accurate estimate of this new,
and, as we venture to think, highly important
subject, patience for the following general con-
sideration." Then follows in succeeding
pages these considerations. It has remained
for our sagacious German critic to make the
discovery that all this acknowledgment refers
only to the "first page," in spite^of the con-
text as given above !
It is much to his credit that no one else has
ever been accurate enough to make this aston-
ishing discovery, not even the " American
reader," who will even find difficulty in seeing
it when pointed out. As to Prof. Weyrauch,
who ought certainly to be the best judge of
what is due himself — he has expressed himself
as highly pleased and gratified. But then he
is not an "American reader," or rather, he is a
much better one than our critic. My intimacy
with him justifies me in the promise that he
will himself answer in my behalf, over his own
572
VAN NOSTRAND7S ENGINEERING MAGAZINE.
name, this accusation in the Journal, where it
originated, when, of course, you, Mr. Editor,
wiil be only too delighted to translate it also
for the benefit of the much enduring "Ameri-
can reader."
When I add that Prof. Weyrauch's little
pamphlet is of popular interest, that it was
received by me while the book itself was in
press and inserted by way of a popular intro-
duction, and that it is entirely separate and
apart from the body of the work, with which
it has nothing whatever to do, I am sure
this same "American reader" will be lost in
admiration at the amiable temper of our critic,
and will wonder at the acuteness which discov-
ered so much — which has no connection what-
ever with the book proper, to growl about.
I have stated in my Preface, and wish to
repeat here, once for all, that I have indicated
fully all obligations, and have been glad to do
so, as much for my own credit as for the ad-
vantage of the student. Such references are
not as frequent in many works of higher pre-
tensions as they might or ought to be. I have
yet to learn of any dissatisfaction with my
" method of reference " from those concerned.
On the contrary, the kind expressions I have
received are a sufficient answer to any such
imaginary charges from incompetent sources.
The critic's incompetency peeps out in many
places. For instance, he insinuates doubt as
to the thoroughness of my study of " Favaro
and others." Considering that Favaro ap-
peared later and has studied and acknowledged
indebtedness to me, I am inclined to the same
suspicion as regards our German friend.
The sum total is, that, with considerable labor
and a pretty fair knowledge of my subject, I
have produced a work which', whatever its
demerits, can at least lay claim to honest in-
tention and execution, and which is not devoid
of original merit. I would, therefore, state,
once for all, that any imputations upon my
honesty must not be based upon my work, or
it will be at the risk of the accuser, and may
possibly end in putting him in an unenviable
situation as regards his own honesty of pur-
pose. A. J. Du Bois.
MISCELLANEOUS.
The Population of the Earth. — The fifth
publication of Behni and "Wagner's well-
known "Bevolkerung der Erde," is just out,
giving some elaborate statistics on this subject.
Since the last publication of these statistics
the population of the earth shows a total
increase of 15 millions, partly arising from
natural growth and partly the outcome of new
and more exact censuses. The total popula-
tion is now set down at 1,439,145,300, divided
among the Continents as follows : — Europe,
312,398,480; Asia, 831 millions; Africa, 205,-
219,500; Australia and Polynesia, 4,411,300;
America, 88,116,000. The following table
gives the latest results for the chief countries
in the world : —
EUROPE.
Germany, 1875 42,727,360
Austria- Hungary, 1876 37,350,000
Liechtenstein, 1876 8,664
Switzerland, 1876 2,759,854
Netherlands, 1876 3,865,456
Luxembourg, 1875 205,158
European Russia, 1872 72,392,770
Finland, 1875 1,912, 647
Sweden, 1876 4,429,713
Norway, 1875 1,807,555
Denmark, 1876 1,903,000
Belgium, 1876 5,336,185
France, 1876 36,905,788
Great Britain, 1878. 34,242,966
Faroes, 1876 10,600
Iceland, 1876 71,300
Spain (without Canaries), 1871 16,526,511
Andorra 12,000
Gibraltar, 1873 - 25,143
Portugal (with Azores), 1875 4,319,284
Italy, 1876 27,769,475
European Turkey (before division). 9,573,000
Roumania, 1873 5,073,000
Servia, 1876 1,366,923
Montenegro 185,000
Greece, 1870 1,457,894
Malta, 1873 145,604
ASIA.
Siberia, 1873 3,440,362
Russian Central Asia 4,505,876
Turcoman Region 175,000
Khiva 700,000
Bokhara 2,030,000
Karategin 100,000
Caucasia, 1876... = ... 5,391,744
Asiatic Turkey 17,880,000
Samos, 1877 35,878
Arabia (independent) 3,700,000
Aden, 1872 22,707
Persia 6,000, 000
Afghanistan 4,000,000
Kafiristan 300,000
Beloochistan 350,000
China proper 405,000,000
Chinese border lands, including
Eastern Turkestan & Djungaria. 29,580,000
Hongkong, 1876 ' 139,144
Macao, 1871 71,834
Japan, 1874 33,623,373
British India within British Bur-
mah, 1872 188,421,264
Native States. . . ; 48,110,200
Himalaya States 3,300,000
French Settlements, 1875 271,460
Portuguese do. do 444,617
Ceylon, 1875 2,459,542
Laccadives and Maldives 156,800
British Burmah, 1871 2,747,148
Manipur. . . .' 126,000
Burmah 4, 000, 000
Siam 5, 750,000
Annam 21 ,000,000
French Cochin China, 1875 1,600,000
Cambodia 890,000
Malacca (independent) 290,000
Straits Settlements 308,097
East Indian Islands 34,051,900
AUSTRALIA, &C.
New South Wales, 1876 630,843
Victoria, 1876 841,938
South Australia, 1876 229,630
Queensland, 1876... 187,100
West Australia, 1876 27,321
Tasmania, 1876 105,484
New Zealand and Chatham, 1876 . . 444,545
Rest of Polynesia 1,896,090
VAN NOSTRAND'S ENGINEERING MAGAZINE. 97
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Rose, M. E. With 250 illustrations. Crown 8vo, cloth, $2.50.
THE ANEROID BAROMETER: Its Construction and Use. Compiled from Several
Sources. 18mo, boards, 50c; full roan, $1.00.
MATTER AND MOTION. By J. Clerk Maxwell, M. A., LL.D. 18mo, boards, 50c.
ENGINEERS, CONTRACTORS AND SURVEYORS' POCKET TABLE BOOK. By J. M.
Scribner. Tenth edition, revised. Pocket form, full roan, $1.50.
ENGINEERS AND MECHANICS' COMPANION. Eighteenth edition, revised, Pocket
form, full roan, $1.50.
THE STAR FINDER, or Planisphere with a Movable Horizon, and the Names and Magni-
tudes of the Stars and Names of the Constellations, made in accordance with Proctor's
Star Atlas. Printed in colors on fine card board. Price $1.00.
HAND-BOOK OF ELECTRICAL DIAGRAMS AND CONNECTIONS. By C H. Davis,
and Frank B. Rae. Illustrated with 32 full-page illustrations. Second edition, oblong
8vo, extra cloth, $2.00.
%* Copies sent free by mail on receipt of price.
^f° My new catalogue of American and Foreign Scientific Books, 96 pages 8vo, sent to any address, on re-
ceipt of 10 cents.
One Volume, Crown 8vo, Cloth. 350 pp. 250 illustrations. Price, $2.50.
THE
Pattern Maker's Assistant,
EMBRACING LATHE WORK, BRANCH WORK, CORE WORK,
" SWEEP WORK, AND
PRACTICAL GEAR CONSTRUCTION;
THE
IPrepetxa/tiori. and Use of Tools;
TOGETH;. WITH A LARGE COLLECTION OF
USEFUL AND VALUABLE TABLES.
BY
JOSHUA ROSE, M. E.,
AUTHOR OF "COMPLETE PRACTICAL MACHINIST."
COUTE1TTS.
CHAPTER I. — General Remarks ; Selection of Wood ; Warping of Wood ; Drying of Wood ;
Plane-irons ; Grinding Plane-irons ; Descriptions of Planes ; Chisels ; Gouges ; Compasses ; Squares ;
Gages ; Trammels ; Winding-strips ; Screw-driver ; Mallet ; Calipers. Chapter II. — Lathe ;
Lathe Hand-rest ; Lathe Head ; Lathe Tail-stock ; Lathe Fork ; Lathe Chucks ; Gouge ; Skew-
chisel ; Turning Tools. Chapter III. — Molding Flask ; How a Pattern is Molded; Snap Flask.
Chapter IV.— Description of Cores ; Core-boxes ; Examples of Cores ; Swept Core for Pipes, etc.
Chapter V — Solid Gland Pattern ; Molding Solid Gland Pattern; Gland Pattern without Core-
print ; Gland Pattern made in Halves ; Bearing or Brass Pattern ; Rapping Patterns ; Example in
Turning ; Sand-papering ; Pattern Pegs ; Pattern Dog, or Staple ; Varnishing ; Hexagon Gage ;
Scriber. Chapter VI. — Example in T -joints, or Branch Pipes ; Example in Angular Branch Pipes ;
Core Box for Brnch Pipes. Chapter VII. — Double-flanged Pulley; Molding Double-flange
Pulley; Building up Patterns; Shooting-board; Jointing Spokes. Chapter VIII. — Pipe Bend;
Core-Box for pipe Bend; Swept Core for Pipe Bend; Staving or Lagging ; .Lagging Steam
Pipes. Chapter IX. — Goble Valve; Chucking Globe Valve; Core-boxes for Globe
Valve. Chapter X. — Bench-aid Bench-stop; Bench-hook; Mortise and Tenon; Half-lap
Joint; Dovetail Joint; Mitre Box ; Pillow Block. Chapter XI. — Square Column; Block for
Square Column ; Ornaments for Square Column ; Cores for Square Columns ; Patterns for Round
Columns. Chapter XII. — Thin Work; Window Sill; Blocks for Window Sill. Chapter XIII. —
Sweep and Loam-work ; Sweeping up a Boiler ; Sweep Spindle ; Sweeping up an Engine Cylinder.
Chapter XIV. — Gar- wheels ; Construction of Pinion ; Construction of Wheel-teeth ; Gage for
Wheel-teeth ; Bevel Wheels ; Building up Bevel-wheels ; Worm Patterns ; Turning Screw of
Worm Pattern; Cutting Worm by Hand ; Wheel Scale. Chapter XV. — Patterns for Pulleys;
Section Patterns. Chapter XVI. — Cogging; Wood Used for Cogging; Templates for Cog
Teeth ; Sawing out Cogged Teeth ; Boring Cogged Teeth. Chapter XVII.— Machine Tools for
Pattern Making ; Face Lathe ; Jig Saw ; Band Saw ; Circular Saw ; Planing Machine ; Glue Pot.
Chapter XVIII. — Shrinkage of Solid Cylinders; Shrinkage of Globes ; Shrinkage of Disks;
Shrinkage of Round Square Bars ; Shrinkage of Rectangular Tubes ; Shrinkage of U-shaped Cast-
ings ; Shrinkage of Wedge-shaped Casting ; Shrinkage of Ribs on Plates ; General Laws of Shrink-
age ; Table of Shrinkage ; Calculating Thickness of Thin Pipes ; Calculating Thickness of Cylinders
for Hydraulic Presses • Calculating Rims of Flywheels.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Streets, New York.
*#* Copies sent by mail on receipt of price.
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Van NostrancTs Science Series,— No. 36.
16mo, Boards, Illustrated. 216 pp. Price, 50 Cents.
MATTER & MOTION
BY
J. CLERK MAXWELL,
Professor of Experimental Physics in the University of Cambridge.
CONTENTS.
Chapter I — Nature of Physical Science ; Definition of a Material System ; Definition of Internal and
External; Definition of Configuration ; Diagrams; A Material Particle ; Relative Position of two Material
Particles; Vectors; System of three Particles; Addition of Vectors; Subtraction of one Vector from
another ; Origin of Vectors ; Relative Position of Two Systems ; Three Data for the Comparison of Two
Systems ; On the Idea of Space ; Error of Descartes ; On the Idea of Time ; Absolute Space ; Statement
ot the General Maxim of Physical Science. Chapter II., On Motion.— Definition of Displacement ; Diagram
of Displacement; Relative Displacement; Uniform Displacement: On Motion; On the Continuity of
Motion ; On Constant Velocity ; On the Measurement of Velocity when Variable ; Diagram of Veloci-
ties; Properties of the Diagram of Velocities; Meaning of the Phrase "at Rest;" On Change of Velocity;
On Acceleration ; On the Rate of Acceleration ; Diagram of Acceleration ; Acceleration a Relative Term.
Chapter III., On Force. — Kinematics and Kinetics ; Mutual Action between Two Bodies— Stress ; External
Force ; Different Aspects of the same Phenomenon ; Newton's Laws of Motion ; The First Law of Motion ;
On the Equilibrium of Forces ; Definition of Equal Times ; The Second Law of Motion ; Definition of
Equal Masses and of Equal Forces ; Measurement of Mass ; Numerical Measurement of Force ; Simulta-
neous Action of Forces on a Body ; On Impulse ; Relation between Force and Mass ; On Momentum ;
Statement of the Second Law of Motion in Terms of Impulse and Momentum ; Addition of Forces ; The
Third Law of Motion ; Action and Reaction are the Partial Aspects of a Stress; Attraction and Repulsion;
The Third Law True of Action at a Distance ; Newton's Proof not Experimental. Chapter IV., On the
Properties of the Centre of Mass of a Material System.— Definition of a Mass-Vector ; Centre of Mass of
Two Particles ; Centre of Mass of a System ; Momentum Represented at the Rate of Change of a Mass
Vector; Effect of External Forces on the Motion of the Centre of Mass; The Motion of the Centre of Mam
of a System is not affected by the Mutual Action of the Parts of the System; First and Second Laws of
Motion ; Method of Treating Systems ot Molecules; By the Introduction of the Idea of Mass we pass from
Point-Vectors, Point Displacements, Velocities, Total Accelerations, and Rates of Acceleration, to Mass-
Vectors, Mass Displacements, Momenta, Impulse and Moving Forces ; Definition of a Mass-Area ; Angular
Momentum; Moment of a Force about a Point: Conservation of Angular Momentum. Chapter V., On
Work and Energy— Definitions ; Principle of Conservation of Energy ; General Statement of the Prin-
ciple of the Conservation of Energy ; Measurement of Work ; PotentialEnergy ; Kinetic Energy ; Oblique
Forces; Kinetic Energy of Two Panicles Referred to its Centre of Mass ; Available Kinetic Energy ; Poten
tial Energy ; Elasticity ; Action at a Distance ; Theory of a Potential Energy more Complicated than that
of Kinetic Energy; Application of the Method of Energy to the Calculation of Forces ; Specification of
the Direction of Forces ; Application to a System in Motion ; Application of the Method of Energy to the
Investigation of Real Bodies ; Variables on which the Energy Depends ; Energy in Terms of the Variables ;
Theory of Heat ; Heat a Form of Energy ; Energy Measured as Heat ; Scientific Work to be Done ; History
of the Doctrine of Energy ; On the Different Forms of Energy. Chapter VI., Recapitulation.- Retrospect
of Abstract Dynamics ; Kinematics ; Force ; Stress ; Relativity of Dynamical Knowledge ; Relativity of
Force; Rotation; Newton's Determination of the Absolute Velocity of Rotation ; Foucault's Pendulum;
Matter and Energy; Test of a Material Substance ; Energy not Capable of Identification ; Absolute Value
of the Energy of a Body Unknown ; Latent Energy ; A Complete Discussion of Energy would include the
whole of Physical Science. Chapter VII. , The Pendulum and Gravity. — On Uniform Motion in a Circle;
Centrifugal Force ; Periodic Time ; On Simple Harmonic Vibrations ; On the Force Acting on the Vibrating
Body ; Isochronous Vibrations ; Potential Energy of the Vibrating Body ; The Simple Pendulum ; A Rigid
Pendulum ; Inversion of the Pendulum ; Illustrations of Kater's Pendulum ; Determination of the Intensity
of Gravity ; Method of Observation; Estimation of Error. Chapter V 'III., Universal Gravitation. — New-
ton's Method ; Kepler's Laws; Angular Velocity : Motion about the Centre of Mass; The Orbit; The
Hodograph ; Kepler's Second Law; Force on a Planet ; Interpretation of Kepler's Third Lawj Law of
Gravitation ; Amended Form of Kepler's Third Law; Potential Energy due to Gravitation ; Kinetic Energy
of the System; Potential Energy of the System; The Moon is a Heavy Body; Cavendish's Experiment;
The Torsion Balance ; Method of the Experiment ; Universal Gravitation ; Cause of Gravitation ; Appli-
cation of Newton's Method of Investigation ; Methods of Molecular Investigations ; Importance of General
and Elementary Properties.
D. VAN NOSTRAND, Publisher,
23 Murray, and 27 Warren Sts.,
NEW YOUK.
*#* Copies sent by mail on receipt of price.
100 VAN NOSTRAS D'S ENGINEERING MAGAZINE.
One Vol., 8vo., with upwards of two hundred and fifty Illustrations. Cloth. $1.50.
WOOD AND ITS USES.
A HAND-BOOK
FOR THE USE OF
CONTRACTORS, BUILDERS, ARCHITECTS, ENGINEERS,
LUMBER MERCHANTS, Etc.
WITH INFORMATION FOR
DRAWING TJJ? DfCiSIGrVS AND ESTIMATES.
BY
P. B. EASSIE,
Member of the Institution of Mechanical Engineers.
D. TAN NOSTRAND, Publisher, 23 Murray & 27 Warren Sts., N. Y.
*#* Copies sent by mail on receipt cf price.
JEERING ,
MINING
OF NEW YORK AND DENVER COLORADO.
An Illustrated Weekly devoted to
3IIIVI1VO, MJ3T,\.IiL.UR«V JLiSTI> IE1VOITV EEF&IIVO.
28 Pages and Numerous Supplements .
CONDUCTED BY
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ROSSITER W. RAYMOND, Ph.D., Late U. S. Commissioner of Mines.
The Engineering and Mining Journal is the recognized highest authority
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The absolute independence of its financial and other reports, and the accuracy
of its statements, make it of great value to those who are or propose becoming
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VAN NOSTRAND'S ENGINEERING MAGAZINE. 101
THE AMERICAN CHEMIST.
A MONTHLY JOURNAL
OF
Theoretical, Analytical and Technical Chemistry.
EDITED BY
C. F. CHANDLER, P. D., F. C. S,
Professor of Analytical and Applied Chemistry, School of Mines, Columbia College, N. Y. ,and
W. H. CHANDLER, F. C. S.,
Professor of Analytical Chemistry , Lehigh University, Pennsylvania.
This Journal is the medium of communication for the chemists of the country ; not only those who are engaged
in theoretical investigation, hut also those who are devoted to the practical application of Chemistry to the Arts.
The American Chemist is published in monthly numbers, each number containing forty double column quarto
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It contains original articles ; reprints and translations of the most important articles published in this and
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lished in other Journals, and in the Transactions of Learned Societies; Notices of Books; Lists of Chemical
Patents granted at Washington ; Current News relating to Chemists and to Chemistry; Questions from, and
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It is the intention of the Editors to place before its readers everything that will be of interest to Chemists and
those who are engaged in Chemical pursuits.
To this end arrangements have been made by which over one hundred different Journals are now received
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THE
Journal of the Franklin Institute,
! DEVOTED TO SCIENCE AND THE MECHANIC ABTS.
ESTABLISHED IN 1826.
The only Technological Journal published in the United States,
without private pecuniary interest.
Its object is to encourage original research, and disseminate useful knowledge in all
matters relating to the practical application of science, but more especially to engineering
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The Journal is issued in monthly numbers, of seventy-two pages each, largely illus-
trated, forming two volumes annually. The number for June, 1877, completes the One
Hundred and Third volume.
Hereafter its value will be greatly increased by its containing more original matter : by
more attention and space being given to the publication of articles condensed from foreign
and domestic scientific and technical periodicals, with ample references.
More space will also be given to the transactions of the Institute, thus rendering it of
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102
VAN NOSTRAND'S ENGINEERING MAGAZINE.
Just J?ut>lisliecl :
THIRD EDITION OF DR. DAWSON'S WORK
ON THE
L
m
m
if
n J)
OF THE DOMINION
Acadian Geology. The Geological Structure, Organic Remains, and Mineral
Resources of Nova Scotia, New Brunswick, and Prince Edward Island. Third
edition ; with a Geological Map and numerous illustrations. By J. W. Dawson, F.
R.S., F.G.S., Principal of McGill College. Pp. 818; royal 8vo, Cloth, $6.00.
This third edition of Dr. Dawson's important work is brought down to the most
recent date by a Supplement containing all that has been discovered or established,
since the publication of the Second edition, concerning the Geological Structure,
Fossil Remains and Mineral Resources of the Eastern Provinces. The work from
the extent of its scope and the fulness of its detail is absolutely necessary to every one
who may be interested in the development of the resources of these Provinces.
The map is colored geologically, and there are besides in the book over 400 illustra-
tions. The labors of a life time of Scientific research have been expended upon
the elucidation of the Geology of these most interesting provinces, and the results
have been embodied by Principal Dawson in this handsome volume now reaching
to 818 pages of octavo. The Supplement may be had separately by purchasers of the
previous edition; Price, $1.25.
NOTICES OF THE PRESS:
"It requires only a glance at the work to perceive that there is here one of the most important of
modern contributions to the science of Palseontological Botany." — Geological Magazine. London,
Eng.
"The economic geology of the region is kept well to the fore, also its physical geography and
agricultural charateristics are dependant upon its geological structure. Many subjects of great
interest in general geology, are illustrared or described in this volume ; especially the nature of
coal, the flora of coal, preservation of erect trees, origin of gypsum, life in seas, estuaries, etc. , trails,
rain marks and foot prints, albertite, gold, primeval man, etc. Upwards of 270 woodcuts, mostly
excellent in character, a good geological map, and lastly, several lists of contents, special subjects
and illustrations, a valuable appendix and useful index complete this satisfactory, well-written and
well-printed work, on the geology and geological resources of Acadia." — Annals and Magazine of
Natural History. London, Eng.
" The general reader will find many pages of pleasant and lucid description, amplified from the
former work, while the political economist will obtain from it a full description of the mineral
resources of the Acadian Provinces, and statistics of their development during the last decade." — New
York Evening Post.
"It is altogether a work of which the Colony may very justly be proud, for it is not merely a
valuable digest of the geology and palaeontology of Acadia, but an important contribution to the
literature of these sciences." — Pall Mall Gazette. London.
D. VJlJST JSTOSTItJLJSrJD, JPuLbUsUer,
23 Murray & 27 Warren Sts , New York,
*** Copies sent by mail on receipt of price.
One Volume, Quarto, with five full page Views and twelve Folding Plates,
Cloth, $6.00.
the:
KANSAS CITY BRIDGE,
WITH AN ACCOUNT OF THE REG-IMEN OF THE
MISSOURI RIVER,
AND A
Description of Methods used in Pounding in that river.
BY
O. CHANUTE, Chief Engineer,
AND
GEO. MORISON, Assistant Engineer.
TABLE OF CONTENTS.
Chapter I. — History of the Project. Chap. II. — Character of the Work.
Chap. III. — Foundations. Chap. IV. — Masonry. Chap. V. — Superstructure.
Chap. VI.— Outfit. Chap. VII.— Calculated Strength. Chap. VIII— Cost of the
Work. Appendix. — Charters Traffic, July 13, 1869 to February 28, 1870. — Tables
relating to Pier No. 4. Tables of Strains in the Fixed Spans. Tables of Strains in
the Draw. Lists of persons employed.
VIEWS AND PLATES.
View of Kansas City Bridge, August 2, 1869. Lowering Caisson No. 1 into posi-
tion. Caisson for Pier No. 4 brought into position. View of Foundation Works Pier
4. Pier No. 1. Map, showing location of Bridge. Water Record. Cross Sections
of River. Profile or Crossing. Pontoon Protection. Water Decadence. Caisson
No. 2. Foundation Works, Pier No. 3. Foundation Works, Pier No. 4. Caisson
No. 5. Sheet Piling at Pier No. 6. Details of Dredges. Pile Shoe. Beton Box
Masonry. Draw Projection. False Works between Piers 3 and 4. Floating
Derricks. General Elevation, 176 feet span. 248 feet span. Plans of Draw.
Strain Diagrams.
D. VAN NOSTRAND, Publisher,
23 Murray, and 27 Warren Street, New York,
*#* Copies sent by mail on receipt of price.
104 VAN nostrand's engineering magazine.
One Volume, 8vo, cloth, 310 pp, illustrated by 69 lithographic engravings. Price, $6.50 cloth.
$8. 50 half russia binding.
MILITARY BRIDGES
WITH
$u^e$tior\$ of ]^[ew E<xj)ediei\t^ kqd doi^tihidtioi}^
lot dfo^ii}^ j3trekm$ ki\d Ci\k^ir^
INCLUDING ALSO
DESIGNS FOR TRESTLE AND TRUSS BRIDGES, &c.
CONTENTS.
Introduction — Bridges for Military Railroads — Military Railroad Trestle
Bridges — Organization for the construction of the Potomac Creek Viaduct — Military
Truss Bridges — False Works — Transportation and Distribution of Material — Truss
Bridges of Long Spans constructed of Round Sticks — Floating Railway Bridge —
Portable Railway Trusses — Wooden Piers for Military Truss Bridges — Trestle
Bridges for Ordinary Military Railroads — Pile Bridges — Small Truss Bridges —
Suspension Bridges — Military Board Suspension Bridges supported on Trestles —
Floating Bridges — Blanket Boats — Floating Docks, Warehouses and Transports —
Suggestions as to the most expeditious mode of destroying Bridges and Locomotive
Engines — Instructions for the use of Torpedoes — Wire Military Suspension Bridge
— U. S. Pontoon Bridges — India Rubber Pontoon Bridge — Military Bridges in
Europe — Flying Bridges — Bridges on Rafts, Casks, Inflated Skins, etc. — Expedients
for crossing Streams — Substitutes for Anchors — Bridges on Trestles, on Piles and
on Carriages — Simple Trusses — Suspension Bridges — Report to Gen. Halleck on
Blanket Boats.
D. VA-JST JVOSTttJLJSTI), JPizmisTier,
23 Murray and 27 Warren Streets, New York.
*#* Copies sent by mail, postpaid, on receipt of price.
193
RECENT WORKS
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D. VAN NOSTRAND,
23 ^Enrray sund. 27 "Warren Streets,
NEW YORK.
A MANUAL OF RULES, TABLES and DATA for Mechanical Engineers. Based on the
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diagrams. 1012 pages, 8vo., cloth, $7.50 ; half morocco, $10.00.
A PRACTICAL TREATISE OX CHEMISTRY. Qualitative and Quantitative Analysis,
Stoichiometry, Blow-Pipe Analysis, Mineralogy, Assaying, Pharmaceutical Preparations,
Human Secretions. Specific Gravities, Weights and Measures, &c, &c. By Henry A.
Mott, Jr., E.M., Ph.D. 650 pages, 8vo, cloth, $6.00.
QUALITATIVE CHEMICAL ANALYSIS. A Guide in the Practical Study of Chemistry
and in the work of Analysis. By S. H. Douglas and A. B. Prescott, Professors of
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LEGAL CHEMISTRY. A Guide to the Detection of Poisons, Falsifications of Writings,
Adulteration of Alimentary and Pharmaceutical Substances ; Analysis of Ashes, and
Examination of Hair, Coins, Fire- Arms, and Stains, as applied to Chemical Jurispru-
dence. Translated from the French of A. Naquet. By J. P. Battersrajll, Ph.D.
Illustrated. 12mo, cloth, $2.00.
HEATING AND VENTILATION, in their Practical Application for the Use of Engineers
and Architects; embracing a Series of Tables, and Formulas for Dimensions of Heat-
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Schumann, C. E. With Illustrations. 12mo. full roan, $1.50.
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By Edouard Jannettaz. Translated from the French by Prof. George W. Plymp-
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NOTES ON ENGINEERING CONSTRUCTION. Embracing Discussions of the Principles
involved and Descriptions of the Material employed. Bv J. E. Shields, C. E. 12mo,
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THE PATTERN-MAKER'S ASSISTANT. Embracing Lathe Work, Bench Work, Core
Work, Sweep Work, and Practical Gear Construction. The Preparation and Use of
Tools, together with a large collection of Usef ul and Valuable Tables. By Joshua
Rose, M. E. With 250 illustrations. Crown 8vo, cloth, $2.50.
THE ANEROID BAROMETER: Its Construction and Use. Compiled from Several
Sources. 18mo, boards, 50c. ; full roan, $1.00.
MATTER AND MOTION. By J. Clerk Maxwell, M. A., LL.D. 18mo, boards, 50c.
ENGINEERS, CONTRACTORS AND SURVEYORS' POCKET TABLE BOOK. By J. M.
Scribner. Tenth edition, revised. Pocket form, full roan, $1.50.
ENGINEERS AND MECHANICS' COMPANION. Eighteenth edition, revised, Pocket
form, full roan, $1.50.
THE STAR FINDER, or Planisphere with a Movable Horizon, and the Names and Magni*
tudes of the Stars and Names of the Constellations, made in accordance with Proctor's
Star Atlas. Printed in colors on fine card board. Price $1.00.
HAND-BOOK OF ELECTRICAL DIAGRAMS AND CONNECTIONS. By C H. Davis,
and Frank B. Rae. Illustrated with 32 full-page illustrations. Second edition, oblong
8vo, extra cloth, $2.00.
%* Copies sent free by mail on receipt of price.
My new catalogue of American and Foreign Scientific Books, 96 pages 8vo, sent to any address, on re-
ceipt of 10 cents.
One Volume, Crown 8vo, Cloth. 350 pp. 250 illustrations. Price, $2.50.
THE
Pattei^n Maker's Assistant,
EMBRACING LATHE WORK, BRANCH WORK, CORE WORK,
SWEEP WORK, AND
PRACTICAL GEAR CONSTRUCTION;
THE
Preparation, and Use of" Tools;
TOGETHER WITH A LARGE COLLECTION OF
USEFUL AND VALUABLE TABLES.
JOSHUA ROSE, M. E.,
AUTHOR OF "COMPLETE PRACTICAL MACHINIST.'
COITTEITTS.
Chapter I. — General Remarks ; Selection of Wood ; Warping of Wood ; Drying of Wood ;
Plane-irons ; Grinding Plane-irons ; Descriptions of Planes ; Chisels ; Gouges ; Compasses ; Squares ;
Gages; Trammels; Winding-strips; Screw -d river ; Mallet; Calipers. Chapter II. — Lathe;
Lathe Hand-rest ; Lathe Head ; Lathe Tail-stock ; Lathe Fork ; Lathe Chucks ; Gouge ; Skew-
chisel ; Turning Tools. Chapter III. — Molding Flask ; How a Pattern is Molded ; Snap Flask.
Chapter IV.— Description of Cores ; Core-boxes ; Examples of Cores ; Swept Core for Pipes, etc.
Chapter V. — Solid Gland Pattern ; Molding Solid Gland Pattern; Gland Pattern without Core-
print ; Gland Pattern made in Halves ; Bearing or Brass Pattern ; Rapping Patterns ; Example in
Turning ; Sand-papering ; Pattern Pegs ; Pattern Dog, or Staple ; Varnishing ; Hexagon Gage ;
Scriber. Chapter VI. — Example in T -joints, or Branch Pipes ; Example in Angular Branch Pipes ;
Core Box for Br inch Pipes. Chapter VII. — Double-flanged Pulley; Molding Double-flange
Pulley ; Building up Patterns ; Shooting-board ; Jointing Spokes. Chapter VIII. — Pipe Bend ;
Core-Box for pipe Bend; Swept Core for Pipe Bend; Staving or Lagging; Lagging Steam
Pipes. Chapter IX. — Goble Valve; Chucking Globe Valve; Core-boxes for Globe
Valve. ChapTer X. — Bench-aid Bench-stop; Bench-hook; Mortise and Tenon; Half-lap
Joint; Dovetail Joint; Mitre Box ; Pillow Block. Chapter XT. — Square Column; Block for
Square Column ; Ornaments for Square Column ; Cores for Square Columns ; Patterns for Round
Columns. Chapter XII. — Thin Work; Window Sill; Blocks for Window Sill. Chapter XIII. —
Sweep and Loam-work ; Sweeping up a Boiler ; Sweep Spindle ; Sweeping up an Engine Cylinder.
Chapter XIV. — Gar-wheels; Construction of Pinion ; Construction of Wheel-teeth ; Gage for
Wheel- teeth ; Bevel Wheels ; Building up Bevel -wheels ; Worm Patterns ; Turning Screw of
Worm Pattern ; Cutting Worm by Hand ; Wheel Scale. Chapter XV. — Patterns for Pulleys ;
Section Patterns. Chapter XVI. — Cogging; Wood Used for Cogging; Templates for Cog
Teeth ; Sawing out Cogged Teeth ; Boring Cogged Teeth. Chapter XVII. — Machine Tools for
Pattern Making ; Face Lathe ; Jig Saw ; Band Saw ; Circular Saw ; Planing Machine ; Glue Pot.
Chapter XVIII. — Shrinkage of Solid Cylinders; Shrinkage of Globes ; Shrinkage of Disks;
Shrinkage of Round Square Bars ; Shrinkage of Rectangular Tubes ; Shrinkage of U-shaped Cast-
ings ; Shrinkage of Wedge-shaped Casting ; Shrinkage of Ribs on Plates ; General Laws of Shrink-
age ; Table of Shrinkage ; Calculating Thickness of Thin Pipes ; Calculating Thickness of Cylinders
for Hydraulic Presses • Calculating Rims of F1-- wheels.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Streets, New York.
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VAN NOSTRAND'S ENGINEERING MAGAZINE. 195
GEOLOGICAL COMMISSION OF BRAZIL,
PROFESSOR CH. FRED. HARTT, CHIEF.
One Volume, i8mo, boards. 175 pp. Price 50 cents. (Forming No. 37 Van Nostrand's Science
Series.)
GEOGRAPHICAL SURVEYING,
ITS USES, METHODS AND RESULTS,
BY
FRANK DE YEAUX CARPENTER, C. E.,
Geographer to the Commission.
PREFACE.
Charles Frederic Hartt, Professor of Geology in the Cornell University,
and Chief of the Geological Commission of Brazil, died on the eighteenth of March
last, in Rio de Janeiro, where he was engaged in preparing the reports of his Survey.
His death and the dissolution of the Commission, of which he was the founder
and director, have prevented the realization in Brazil of the plan of surveying pro-
posed in the accompanying pages.
F. D. Y. C.
New York, July, 1878.
LATE NUMBERS IN THE SERIES.
24. A Practical Treatise on the Teeth of Wheels, with the Theory and the Use of Robinson's
Odontograph. By S. W. Robinson, Professor of Mechanical Engineering, Illinois Indus-
trial University. Illustrated.
25. On the Theory and Calculation of Continuous Bridges. By Mansfield Merriman, Ph. D.
Illustrated.
26. Practical Treatise on the Properties of Continuous Bridges. By Charles Bender, C. E.
Illustrated.
27. On Boiler Incrustation and Corrosion. By F. J. Rowan.
28. Transmission of Power by Wire Ropes. By Albert W. Stahl, U. S. N. Illustrated.
29. Steam Injectors ; Their Theory and Use. From the French of Leon Pochet.
30. The Magnetism of Iron Vessels, with a Short Treatise on Terrestrial Magnetism. By Fair-
man Rogers.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33. The Mechanics of Ventilation. By Geo. W. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon-Harcourt.
35. The Aneroid, and How to Use it. Compiled by George W. Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Maxwell.
Maximum Stresses in Framed Bridges. By Prof. Wm. Cain. {In Press.}
A Hand Book of the Electro-Magnetic Telegraph. By A. E. Loring. {In Press.)
Price, 50 Cents Each.
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196 van nostrand's engineering magazine.
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WOOD. AND ITS USES.
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FOR THE USE OF
CONTRACTORS, BUILDERS, ARCHITECTS, ENGINEERS,
LUMBER MERCHANTS, Etc.
WITH INFORMATION FOR
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P. B. EASSIE,
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D. VAN NOSTRAND, Publisher, 28 Murray & 27 Warren Sts., N. Y.
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THE AMERICAN CHEMIST.
A MONTHLY JOURNAL
OF
Theoretical, Analytical and Technical Chemistry.
EDITED BY
C. F. CHANDLER, P. D., F. C. S.,
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W. H. CHANDLER, F. C. S.,
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Jixst Pulblislied :
THIRD EDITION OF DR. DAWSON'S WORK
T
J
OF THE DOMINION
Acadian Geology. The Geological Structure, Organic Remains, and Mineral
Resources of Nova Scotia, New Brunswick, and Prince Edward Island. Third
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The map is colored geologically, and there are besides in the book over 400 illustra-
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agricultural charateristics are dependant upon its geological structure. Many subjects of great
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coal, the flora of coal, preservation of erect trees, origin of gypsum, life in seas, estuaries, etc., trails,
rain marks and foot prints, albertite, gold, primeval man, etc. Upwards of 270 woodcuts, mostly
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Natural History. London, Eng.
" The general reader will find many pages of pleasant and lucid description, amplified from the
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valuable digest of the geology and palaeontology of Acadia, but an important contribution to the
literature of these sciences. " — Pall Mall Gazette. London.
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CONTENTS.
Introduction — Bridges for Military Railroads — Military Railroad Trestle
Bridges — Organization for the construction of the Potomac Creek Viaduct — Military
Truss Bridges — False Works — Transportation and Distribution of Material — Truss
Bridges of Long Spans constructed of Round Sticks — Floating Railway Bridge —
Portable Railway Trusses — Wooden Piers for Military Truss Bridges — Trestle
Bridges for Ordinary Military Railroads — Pile Bridges — Small Truss Bridges —
Suspension Bridges — Military Board Suspension Bridges supported on Trestles —
Floating Bridges — Blanket Boats — Floating Docks, Warehouses and Transports —
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— U. S. Pontoon Bridges — India Rubber Pontoon Bridge — Military Bridges in
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for crossing Streams — Substitutes for Anchors — Bridges on Trestles, on Piles and
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American Jourhal of Mathematics,
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Hopkins University.
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numbers, appearing quarterly. First volume
now being published.
Editor in Chiefs J. J. Sylvester, LL.D., F. R. S., Corr. Mem. Inst, of France ; Associate
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the American Ephemeris, and H. A. Rowland, C. E., of the Johns Hopkins University.
Contents of the first and second numbers (already published) of Vol, I.
Note on a Class of Transformations which Surfaces may undergo in Space of more than Three Dimensions. By
Simon Newcomb. Researches in the Lunar Theory. I and II. By G. W. Hill, Nyack Turnpike, N. Y. The
Theorem of Three Moments. By Henry T. Eddy, University of Cincinnati. Solution of the Irreducible Case.
By Guido Weichold, Zittau, Saxony. Desiderata and Suggestions. By Professor Cayley, Cambridge , Eng-
land. No. i — The Theory of Groups. No. 2 — The Theory of Groups; Graphical Representation. Note on the
Theory of Electric Absorption. By H. A. Rowland. Esposizione del Metodo dei Minimi Quadrati. Per Anni-
bale Ferrero, Tenente Colonnello di Stato Maggiore , ec . Firenze, 1876. By Charles S. Peirce, New York.
On an application of the New Atomic Theory to the Graphical Representation of the Invariants and Covariants of
Binary Quantics. By J. J. Sylvester. Appendix 1. On Differentiants Expressed in Terms of the Differences of
the Roots of their Parent Quantics. Appendix 2. On M. Hermite's Law of Reciprocity. Appendix 3. On
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Extract of a Letter to Mr. Sylvester from Professor Clifford of University College, London. Bipunctual Coordinates.
By F. Franklin, Fellow of the Johns Hopkins University. On the Elastic Potential of Crystals. By William
E. Story. Theorie des Fonctions Numeriques Simplement Periodiques. (To be continued.) Par Edouard
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VAN NOSTRAND S ENGINEERING MAGAZINE.
289
RECENT WORKS
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T HE
T attef^n Maker's Assistant,
EMBRACING LATHE WORK, BRANCH WORK, CORE WORK,
SWEEP WORK, AND
PRACTICAL GEAR CONSTRUCTION;
THE
IPrepaxa/tiozi. and Use of 'Tools;
togethk;. with a large collection of
USEFUL AND VALUABLE TABLES.
BY
JOSHUA ROSE, M. E.,
AUTHOR OP "COMPLETE PRACTICAL MACHINIST."
CO^TTEITTS.
Chapter I. — General Remarks ; Selection of Wood ; Warping of Wood ; Drying of Wood ;
Plane-irons ; Grinding Plane-irons ; Descriptions of Planes ; Chisels ; Gouges ; Compasses ; Squares ;
Gages; Trammels; Winding-strips; Screw-driver; Mallet; Calipers. Chapter II. — Lathe;
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chisel ; Turning Tools. Chapter III.— Molding Flask ; How a Pattern is Molded ; Snap Flask.
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Chapter V. — Solid Gland Pattern ; Molding Solid Gland Pattern; Gland Pattern without Core-
print ; Gland Pattern made in Halves ; Bearing or Brass Pattern ; Rapping Patterns ; Example in
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Scriber. Chapter VI. — Example in T -joints, or Branch Pipes ; Example in Angular Branch Pipes ;
Core Box for Branch Pipes. Chapter VII. — Double-flanged Pulley; Molding Double- flange
Pulley ; Building up Patterns ; Shooting-board ; Jointing Spokes. Chapter VIII. — Pipe Bend ;
Core-Box for pipe Bend ; Swept Core for Pipe Bend ; Staving or Lagging ; Lagging Steam
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Joint; Dovetail Joint; Mitre Box ; Pillow Block. Chapter XL — Square Column; Block for
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Columns. Chapter XII. —Thin Work; Window Sill; Blocks for Window Sill. Chapter XIII. —
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Chapter XIV. — Gar-wheels; Construction of Pinion ; Construction of Wheel-teeth ; Gage for
Wheel- teeth ; Bevel Wheels ; Building up Bevel -wheels ; Worm Patterns ; Turning Screw of
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Chapter XVIII. — Shrinkage of Solid Cylinders; Shrinkage of Globes ; Shrinkage of Disks;
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age ; Table of Shrinkage ; Calculating Thickness of Thin Pipes ; Calculating Thickness of Cylinders
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VAN NOSTRAND'S ENGINEERING MAGAZINE. 291
GEOLOGICAL COMMISSION OF BRAZIL,
PROFESSOR CH. FRED. HARTT, CHIEF.
One Volume, i8mo, boards. 175 pp. Price 50 cents. (Forming No. 37 Van Nostrand's Science
Series.) •
GEOGRAPHICAL SURVEYING,
ITS USES, METHODS AND RESULTS,
BY
FRANK DE YEAUX CARPENTER, C. E.,
Geographer to the Commission.
PEEFACE.
Charles Frederic Hartt, Professor of Geology in the Cornell University,
and Chief of the Geological Commission of Brazil, died on the eighteenth of March
last, in Rio de Janeiro, where he was engaged in preparing the reports of his Survey.
His death and the dissolution of the Commission, of which he was the founder
and director, have prevented the realization in Brazil of the plan of surveying pro-
posed in the accompanying pages.
F. D. Y. C.
New York, July, 1878.
LATE NUMBERS IN THE SERIES.
24. A Practical Treatise on the Teeth of Wheels, with the Theory and the Use of Robinson's
Odontograph. By S. W. Robinson, Professor of Mechanical Engineering, Illinois Indus-
trial University. Illustrated.
25. On the Theory and Calculation of Continuous Bridges. By Mansfield Merriman, Ph. D.
Illustrated.
26. Practical Treatise on the Properties of Continuous Bridges. By Charles Bender, C. E.
Illustrated.
27. On Boiler Incrustation and Corrosion. By F. J. Rowan.
28. Transmission of Power by Wire Ropes. By Albert W. Stahl, U. S. N. Illustrated.
29. Steam Injectors ; Their Theory and Use. From the French of Leon Pochet.
30. The Magnetism of Iron Vessels, with a Short Treatise on Terrestrial Magnetism. By Fair-
man Rogers.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33. The Mechanics of Ventilation. By Geo. W. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon-Harcourt.
35. The Aneroid, and How to Use it. Compiled by George W. Plympton. Illustrated.
36. Matter and Motion By J. Clerk Maxwell.
Maximum Stresses in Framed Bridges. By Prof. Wm. Cain, (hi Press.)
A Hand Book of the Electro-Magnetic Telegraph. By A. E. Loring. (In Press.)
Price, 50 Cents Each.
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292 van nostrand's engineering magazine.
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WOOD AND ITS USES.
A. HAND-BOOK
FOR THE USE OF
CONTRACTORS, BUILDERS, ARCHITECTS, ENGINEERS,
LUMBER MERCHANTS, Etc.
WITH INFORMATION FOR
J3RAWJ1XG- TJJ? DESIGNS AND ESTI31ATES.
BY
P. B. EASSIE,
Member of the Institution of Mechanical Engineers.
D. VAN NOSTRAND, Publisher, 28 Murray & 27 Warren Sts., N. Y.
*#* Copies sent by mail on receipt of price.
THE^Gl_rDj0UftNAL
MINING
OF NEW YORK, AND DENVER, COLORADO.
An Illustrated Weekly devoted to
MINING, METALLURGY AND ENGINEERING.
28 Pages and Numerous Supplements.
CONDUCTED BY
RICHARD P. ROTHWELL, Mining Engineer.
ROSSITER W. RAYMOND, Ph.D., Late U. S. Commissioner of Mines.
The Engineering and Mining Journal is the recognized highest authority
in America on all questions of Mining, Metallurgy, and Engineering, and has the
largest circulation and greatest influence of any newspaper in the United States,
devoted to these subjects.
It gives full and reliable information on all subjects connected .with the Mining,
and Marketing of Coal.
Its statistics of Coal Production are accepted by the United States Government
as the only accurate reports published.
The gold and silver mining interests of the West are fully represented, the Jour-
nal having an office at Denver, Colorado, under the charge of Mr. T. F. Van Wag-
enen, and having the ablest engineers throughout the country for special
correspondents.
The Engineering and Mining Journal publishes also full and accurate trade
reports on Iron, Metals, Mining and other Stocks.
The absolute independence of its financial and other reports, and the accuracy
of its statements, make it of great value to those who are or propose becoming
interested in Mining Investments of any kind in America.
Subscription Price, including postage, $4. Foreign Countries, $5. = £1.=25 Francs,
=20 Marks.
Should be sent by Post Office or Bank Order on New York.
Specimen Copies sent free on application.
VAN NOSTRAND'S ENGINEERING MAGAZINE. . 293
•-
THE AMERICAN CHEMIST.
A MONTHLY JOURNAL
OF
Theoretical, Analytical and Technical Chemistry.
EDITED BY
C. F. CHANDLER, P. D., F. C. S ,
Professor of Analytical and Applied Chemistry, School of Mines, Columbia College, N.Y.,and
W. H. CHANDLER, F. C. ft,
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294
VAN NOSTRAND S ENGINEERING MAGAZINE.
Just Fulblisliecl:
THIRD EDITION OF DR. DAWSON'S WORK
ON THE
u
I
I)
OF THE DOMINION.
Acadian Geology. The Geological Structure, Organic Remains, and Mineral
Resources of Nova Scotia, New Brunswick, and Prince Edward Island. Third
edition ; with a Geological Map and numerous illustrations. By J. W. Dawson, F.
R.S., F.G.S., Principal of McGill College. Pp. 818; royal 8vo, Cloth, $6.00.
This third edition of Dr. Dawson's important work is brought down to the most
recent date by a Supplement containing all that has been discovered or established,
since the publication of the Second edition, concerning the Geological Structure,
Fossil Remains and Mineral Resources of the Eastern Provinces. The work from
the extent of its scope and the fulness of its detail is absolutely necessary to every one
who may be interested in the development of the resources of these Provinces.
The map is colored geologically, and there are besides in the book over 400 illustra-
tions. The labors of a life time of Scientific research have been expended upon
the elucidation of the Geology of these most interesting provinces, and the results
have been embodied by Principal Dawson in this handsome volume now reaching
to 818 pages of octavo. The Supplement may be had separately by purchasers of the
previous edition; Price, $1.25.
NOTICES OF THE PRESS:
' ' It requires only a glance at the work to perceive that there is here one of the most important of
modern contributions to the science of Pabeontological Botany." — Geological Magazine. London,
Eng.
1 ' The economic geology of the region is kept well to the fore, also its physical geography and
agricultural characteristics are dependent upon its geological structure. Many subjects of great
interest in general geology, are illustrated or described in this volume ; especially the nature of
coal, the flora of coal, preservation of erect trees, origin of gypsum, life in seas, estuaries, etc. , trails,
rain marks and foot prints, albertite, gold, primeval man, etc. Upwards of 270 woodcuts, mostly
excellent in character, a good geological map, and lastly, several lists of contents, special subjects
and illustrations, a valuable appendix and useful index complete this satisfactory, well- written and
well-printed work, on the geology and geological resources of Acadia." — Annals and Magazine of
Natural History. London, Eng.
" The general reader will find many pages of pleasant and lucid description, amplified from the
former work, while the political economist will obtain from it a full description of the mineral
resources of the Acadian Provinces, and statistics of their development during the last decade." — New
York Evening Post.
"It is altogether a work of which the Colony may very justly be proud, for it is not merely a
valuable digest of the geology and palaeontology of Acadia, but an important contribution to the
literature of these sciences. " — Pall Mall Gazette. London.
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VAN NOSTRAND'S ENGINEERING MAGAZINE. 387
•Just Publisliecl :
THIRD EDITION OF DR. DAWSON'S WORK
ON THE
I § TIE 111 PROVINCES
OF THE DOMINION.
Acadian Geology. The Geological Structure, Organic Remains, and Mineral
Resources of Nova Scotia, New Brunswick, and Prince Edward Island. Third
edition ; with a Geological Map and numerous illustrations. By J. W. Dawson, F.
R.S., F.G.S., Principal of McGill College. Pp. 818; royal 8vo, Cloth, $6.00.
Thic third edition of Dr. Dawson's important work is brought down to the most
recent date by a Supplement containing all that has been discovered or established,
since the publication of the Second edition, concerning the Geological Structure,
Fossil Remains and Mineral Resources of the Eastern Provinces. The work from
the extent of its scope and the fulness of its detail is absolutely necessary to every one
who may be interested in the development of the resources of these Provinces.
The map is colored geologically, and there are besides in the book over 400 illustra-
tions. The labors of a life time of Scientific research have been expended upon
the elucidation of the Geology of these most interesting provinces, and the results
have been embodied by Principal Dawson in this handsome volume now reaching
to 818 pages of octavo. The Supplement may be had separately by purchasers of the
previous edition; Price, $1.25.
NOTICES OF THE PRESS:
" It requires only a glance at the work to perceive that there is here one of the most important of
modern contributions to the science of Palaeontological Botany." — Geological Magazine. London,
Eng.
" The economic geology of the region is kept well to the fore, also its physical geography and
agricultural characteristics are dependent upon its geological structure. Many subjects of great
interest in general geology, are illustrated or described in this volume ; especially the nature of
coal, the flora of coal, preservation of erect trees, origin of gypsum, life in seas, estuaries, etc., trails,
rain marks and foot prints, albertite, gold, primeval man, etc. Upwards of 270 woodcuts, mostly
excellent in character, a good geological map, and lastly, several lists of contents, special subjects
and illustrations, a valuable appendix and useful index complete this satisfactory, well-written and
well-printed work, on the geology and geological resources of Acadia." — Annals and Magazine of
Natural History, London, Eng.
"The general reader will find many pages of pleasant and lucid description, amplified from the
former work, while the political economist will obtain from it a full description of the mineral
resources of the Acadian Provinces, and statistics of their development during the last decade." — New
York Evening Post.
"It is altogether a work of which the Colony may very justly be proud, for it is not merely a
valuable digest of the geology and palaeontology of Acadia, but an important contribution to the
literature of these sciences." — Pall Mall Gazette. London.
JD. VJlJST JSrOSTttJLJSTD, JPtzbltsKer,
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THE AMERICAN CHEMIST.
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Hereafter its value will be greatly increased by its containing more original matter : by
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GEOLOGICAL COMMISSION OF BRAZIL,
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GEOGRAPHICAL SURVEYING,
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PREPACE.
Charles Frederic Hartt, Professor of Geology in the Cornell University,
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LATE NUMBERS IN THE SERIES.
24. A Practical Treatise on the Teeth of Wheels, with the Theory and the Use of Robinson's
Odontograph. By S. W. Robinson, Professor of Mechanical Engineering, Illinois Indus-
trial University. Illustrated.
25. On the Theory and Calculation of Continuous Bridges. By Mansfield Merriman, Ph. D.
Illustrated.
26. Practical Treatise on the Properties of Continuous Bridges. By Charles Bender, C. E.
Illustrated.
27. On Boiler Incrustation and Corrosion. By F. J. Rowan.
28. Transmission of Power by Wire Ropes. By Albert W. Stahl, U. S. N. Illustrated.
29. Steam Injectors ; Their Theory and Use. From the French of Leon Pochet.
30. The Magnetism of Iron Vessels, with a Short Treatise on Terrestrial Magnetism. By Fair-
man Rogers.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33. The Mechanics of Ventilation. By Geo. W. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon- Harcourt.
35. The Aneroid, and How to Use it. Compiled by George W. Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Maxwell.
Maximum Stresses in Framed Bridges. By Prof. Wm. Cain. (In Press.}
A Hand Book of the Electro-Magnetic Telegraph. By A. E. Loring. {In Press.}
Price, 50 Cents Each.
JD. VJLJST JSrOSTHJLJSm, JPuLbltsKer,
23 Murray and 27 Warren Streets, New York.
*#* Copies sent by mail, postpaid, on receipt of price.
VAN NOSTRAND'S ENGINEERING MAGAZINE. 391
New Number of the Science Series Just ready.
MAXIMUM STRESSES
IN
FRAMED BRIDGES.
BY
Prof. WM. CAIN, A.M., C.E.,
Author of a "Practical Theory of Voimoir Arches."
ILLUSTRATED.
PREFACE
This treatise is clearly a proper supplement to the ordinary works on strains in
trusses. Every case of examination into causes of failure of broken structures
furnishes substantial evidence that such a treatise is an important addition to the
literature heretofore published.
The thoroughly practical character of all of Prof. Cain's literary works, and the
nattering reception of his previous work ( Voussoir Arches) by working engineeers,
have induced the publisher to reprint these recent contributions to the Magazine in
the Science Series.
LATE NUMBERS IN THE SERIES.
24. A Practical Treatise on the Teeth of Wheels, with the Theory and Use of Robinson's
Odontograph. By S. W. Robinson, Professor of Mechanical Engineering, Illinois Indus-
trial University. Illustrated.
25. On the Theory and Calculation of Continuous Bridges. By Mansfield Merriman, Ph. D.
Illustrated.
26. Practical Treatise on the Properties of Continuous Bridges. By Charles Bender, C. E.
Illustrated.
27. On Boiler Incrustation and Corrosion. By E. J. Rowan.
28. Transmission of Power by Wire Ropes. By Albert W. Stahl, U. S. N. Illustrated.
29. Steam Injectors ; Their Theory and Use. From the French of Leon Pochet.
30. The Magnetism of Iron Vessels, with a Short Treatise on Terrestrial Magnetism. By Fair-
man Rogers.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the Construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33. The Mechanics of Ventilation. By Geo. W. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon-Harcourt.
35. The Aneroid, and How to Use it. Compiled by George W. Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Maxwell.
37. Geographical Surveying, its Uses, Methods, and Results. By Frank De Yeaux Carpenter.
39. A Hand Book of the Electro-Magnetic Telegraph. By A. E. Loring. {In Press.)
Price 50 Cents Each.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Streets, New York,
%* Copies sent by mail, post paid, on receipt of price.
392 VAN nosteand's engineering magazine.
One Volume, 8vo, 180 pp., illustrated. New, revised and enlarged edition.
Cloth, $1.50.
MANUAL OF
FOR THE USE OF STUDENTS IN COLLEGES AND
NORMAL AND HIGH SCHOOLS,
BY
GEO. C. CALDWELL, S. B., Ph. D.,
Professor of Agricultural and A nalytical Chemistry
AND
ABRAM A. BRENEMAN, S. B.,
Assistant Professor of Applied Chemistry.
IN CORNELL UNIVERSITY.
SECOND EDITION, REVISED AND CORRECTED
EXTRACT FROM PREFACE TO FIRST EDITION.
This work is the result of a preliminary trial made with a class in the chemical
laboratory of Cornell University in the Fall term of 1874. A small part of the
matter contained in it was printed then in detached sheets for the use of the
students. The work will be found on examination to present a mode of chemical
practice which has the merit at least of novelty, and the experience of the authors
justifies their expectations that it will be found to possess the more important merit
of efficiency.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Streets, New York.
"^Copies sent free by mail on receipt of price.
VAN NOSTRAND'S ENGINEERING MAGAZINE. 481
No. 39 of" the Science Series now ready.
A. VALTJ AISLE ADDITION.
A HAND-BOOK
OF THE
ELECTRO MAGNETIC
TELEGRAPH.
A Practical Telegrapher.
INTRODUCTION.
It has been the aim of the author in the preparation of this little book, to present the principles
of the Electro Magnetic Telegraph, in a brief, concise manner, for the benefit of practical
operators and students of telegraphy. The works on telegraphy which have thus far been
presented, besides being expensive, have contained much that is useless, or which is not in a form to
be readily understood by young and inexperienced telegraphers. Although this little work must be
acknowledged incomplete, it is hoped that it may go far toward supplying the deficiency which has
existed ; or, at least, serve as a stepping-stone to the study of the more complete works on electricity
and telegraphy.
THE AUTHOR.
CONTENTS.
Part I.— Electricity and Magnetism.— Electricity— Positive and Negative. Conductors and Non-Conductors.
Galvanic Batteries. Galvanic Circuits. Electrical Quantity and Intensity. Resistance. Electro-Motive
Force. Haskin's Galvanometer and its Uses. Ohms Law. Measurement of Currents. Measurement of
Resistance. Speed of the Current. Divided Circuits. Electro-Magnets. Residual Magnetism. Proportion
of Electro-Magnets to Circuits. Intensity and Quantity Magnets.
Part II. — The Morse Telegraph. — Fundamental Principle. Telegraph Circuits. Intermediate offices. The
Local Circuit. Ground Wires. The Key. The Relay. The Sounder. Main Line Sounders. The Box
Relay. Cut Outs. The Switch Board. Other Switches. Lightning Arresters. Loops. Arrangement of
Offices. Arrangement of Batteries. Repeaters.
Part III.— Batteries. — Grove Battery. Carbon Battery. Amalgamation of Zincs. Daniell Battery. Hill
Battery. Other Forms of Battery. Battery Insulators.
Part IV.— Practical Telegraphy.— Alphabet and Numerals. Adjustment of Instruments. Testing Telegraph
Lines. Breaks. Escapes. Grounds. Crosses.
Part V.— Construction of Lines. — The Conductors. The Insulators. Fitting up Offices. Ground Wire
Connections. Private and Short Lines.
Appendix. — Suggestions and Exercises for Learners.
Paper Boards, 50 cents, Cloth, 75 cents, Morocco, $i.oo.
LATE NUMBERS IN THE SERIES.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the Construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33- The Mechanics of Ventilation. By Geo. W. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon-Harcourt.
Illustrated.
The Aneroid, and How to Use it. Compiled by Geo. W. Plympton. Illustrated.
Matter and Motion. By J. Clerk Maxwell.
Geographical Surveying, Its Uses, Methods and Results. By Frank De Yeaux Carpenter.
Maximum Stresses in Framed Bridges. By Prof. Wm. Cain. Illustrated.
Transmission of Power by Compressed Air. By Robert Zahner, M. E. (In Press).
On the Strength of Materials. By Wm. Kent, M. E. (In Press).
Price 50 Cents Each.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Streets, New York.
*x* Copies sent by mail, post paid, on receipt of price.
One Volume, Crown 8vo, Cloth. 350 pp. 250 illustrations. Price, $2.50.
THE
Pattern Maker's Assistant,
EMBRACING LATHE WORK, BRANCH WORK, CORE WORK,
SWEEP WORK, AND
PRACTICAL GEAR CONSTRUCTION;
ZEPreparatiorL sun.d. "CTse of Tools
TOGETHER WITH A LARGE COLLECTION OF
USEFUL AND VALUABLE TABLES.
BY
JOSHUA ROSE, M. E.,
AUTHOR OF "COMPLETE PRACTICAL MACHINIST."
COITTEITTS.
Chapter I. — General Remarks ; Selection of Wood ; Warping of Wood ; Drying of Wood ;
Plane-irons ; Grinding Plane-irons ; Descriptions of Planes ; Chisels ; Gouges ; Compasses ; Squares ;
Gages; Trammels; Winding-strips; Screw-driver; Mallet; Calipers. Chapter II. — Lathe;
Lathe Hand-rest ; Lathe Head ; Lathe Tail-stock ; Lathe Fork ; Lathe Chucks ; Gouge ; Skew-
chisel ; Turning Tools. Chapter III.— Molding Flask ; How a Pattern is Molded ; Snap Flask.
Chapter IV. — Description of Cores ; Core -boxes ; Examples of Cores ; Swept Core for Pipes, etc.
Chapter V. — Solid Gland Pattern ; Molding Solid Gland Pattern; Gland Pattern without Core-
print ; Gland Pattern made in Halves ; Bearing or Brass Pattern ; Rapping Patterns ; Example in
Turning ; Sand-papering ; Pattern Pegs ; Pattern Dog, or Staple ; Varnishing ; Hexagon Gage ;
Scriber. Chapter VI. — Example in T -joints, or Branch Pipes ; Example in Angular Branch Pipes ;
Core Box for Branch Pipes. Chapter VII. — Double-flanged Pulley; Molding Double-flange
Pulley; Building up Patterns; Shooting-board; Jointing Spokes. Chapter VIII. — Pipe Bend;
Core-Box for pipe Bend ; Swept Core for Pipe Bend ; Staving or Lagging ; Lagging Steam
Pipes. Chapter IX. — Goble Valve; Chucking Globe Valve; Core-boxes for Globe
Valve. Chapter X. — Bench-aid Bench-stop; Bench-hook; Mortise and Tenon; Half-lap
Joint; Dovetail Joint; Mitre Box; Pillow Block. Chapter XI. — Square Column; Block for
Square Column ; Ornaments for Square Column ; Cores for Square Columns ; Patterns for Round
Columns. Chapter XII. —Thin Work; Window Sill; Blocks for Window Sill. Chapter XIII. —
Sweep and Loam-work ; Sweeping up a Boiler ; Sweep Spindle ; Sweeping up an Engine Cylinder.
Chapter XIV. — Gar- wheels ; Construction of Pinion ; Construction of Wheel-teeth ; Gage for
Wheel- teeth ; Bevel Wheels ; Building up Bevel -wheels ; Worm Patterns ; Turning Screw of
Worm Pattern; Cutting Worm by Hand ; Wheel Scale. Chapter XV. — Patterns for Pulleys;
Section Patterns. Chapter XVI. — Cogging; Wood Used for Cogging; Templates for Cog
Teeth ; Sawing out Cogged Teeth ; Boring Cogged Teeth. Chapter XVII. — Machine Tools for
Pattern Making ; Face Lathe ; Jig Saw ; Band Saw ; Circular Saw ; Planing Machine ; Glue Pot.
Chapter XVIII. — Shrinkage of Solid Cylinders; Shrinkage of Globes ; Shrinkage of Disks;
Shrinkage of Round Square Bars ; Shrinkage of Rectangular Tubes ; Shrinkage of U-shaped Cast-
ings ; Shrinkage of Wedge-shaped Casting ; Shrinkage of Ribs on Plates ; General Laws of Shrink-
age ; Table of Shrinkage ; Calculating Thickness of Thin Pipes ; Calculating Thickness of Cylinders
for Hydraulic Presses • Calculating Rims of Fl"- wheels.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Streets, New York.
*#* Copies sent by mail on receipt of price.
VAN NOSTKAND'S ENGINEERING MAGAZINE. 483
RECENT WORKS
PUBLISHED BY
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23 Is/LxiTTSuy sund. 27 Warren Streets,
NEW YORK.
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A PRACTICAL TREATISE ON CHEMISTRY. Qualitative and Quantitative Analysis,
Stoichiometry, Blow-Pipe Analysis, Mineralogy, Assaying, Pharmaceutical Preparations,
Human Secretions. Specific Gravities, Weights and Measures, &c, &c. By Henry A.
Mott, Jr., E.M.. Ph.D. 650 pages, 8vo, cloth, $6.00.
QUALITATIVE CHEMICAL ANALYSIS. A Guide in the Practical Study of Chemistry
and in the work of Analysis. By S. H. Douglas and A. B. Prescott, Professors of
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LEGAL CHEMISTRY. A Guide to the Detection of Poisons, Falsifications of Writings,
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Examination of Hair, Coins, Fire-Arms, and Stains, as applied to Chemical Jurispru-
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Illustrated. 12mo, cloth, $2.00.
HEATING AND VENTILATION, in their Practical Application for the Use of Engineers
and Architects; embracing a Series of Tables, and Formulas for Dimensions of Heat-
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By Edouakd Jannettaz. Translated from the French by Prof. George W. Plymp-
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NOTES ON ENGINEERING CONSTRUCTION. Embracing Discussions of the Principles
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STRUCTIONS with reference to the latest experiments. By J. J. Weyrauch. With
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THE PATTERN-MAKER'S ASSISTANT. Embracing Lathe Work, Bench Work, Core
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Rose, M. E. With 250 illustrations. Crown 8vo, cloth, $2.50.
THE ANEROID BAROMETER: Its Construction and Use. Compiled from Several
Sources. 18mo, boards, 50c; full roan, $1.00.
MATTER AND MOTION. By J. Clerk Maxwell M. A., LL.D. 18mo, boards, 50c.
ENGINEERS, CONTRACTORS AND SURVEYORS' POCKET TABLE BOOK. By J. M.
Scribner. Tenth edition, revised. Pocket form, full roan, $1.50.
ENGINEERS AND MECHANICS' COMPANION. Eighteenth edition, revised, Pocket
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tudes of the Stars and Names of the Constellations, made in accordance with Proctor's
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HAND-BOOK OF ELECTRICAL DIAGRAMS AND CONNECTIONS. By C H. Davis,
and Frank B. Rae. Illustrated with 32 full-page illustrations. Second edition, oblong
8vo, extra cloth, $2.00.
*»* Copies sent free by mail on receipt of price.
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484 van nostrand's engineering magazine.
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WOOD AND ITS USES.
A. HAND-BOOK
FOR THE USE OF
CONTRACTORS, BUILDERS, ARCHITECTS, ENGINEERS,
LUMBER MERCHANTS, Etc.
WITH INFORMATION FOR
DRAWING UP DESIGNS AJXD ESTIMATES.
BY
P. B. EASSIE,
Member of the Institution of Mechanical Engineers.
D. VAN NOSTRAND, Publisher, 23 Murray & 27 Warren Sts., ». Y.
*#* Copies sent by mail on receipt of price.
SNEERING
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MINING Ju
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An Illustrated Weekly devoted to
MINING, METALLURGY ANI> ENGINEERING.
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CONDUCTED BY
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VAN NOSTRAND'S ENGINEERING MAGAZINE. 485
THE AMERICAN CHEMIST.
A MONTHLY JOURNAL
OP
Theoretical, Analytical and Technical Chemistry.
EDITED BY
C. F. CHANDLER, P. D., F. C. S.,
Professor of Analytical and Applied Chemistry, School of Mines, Columbia College, N.Y.,and
W. H. CHANDLER, F. C. S.,
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This Journal is the medium of communication for the chemists of the country ; not only those who are engaged
in theoretical investigation, but also those who are devoted to the practical application of Chemistry to the Arts.
The American Chemist is published in monthly numbers, each number containing forty double column quarto
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It is the intention of the Editors to place before its readers everything that will be of interest to Chemists and
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The Journal is issued in monthly numbers, of seventy-two pages each, largely illus-
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Hereafter its value will be greatly increased by its containing more original matter : by
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More space will also be gi 7en to the transactions of the Institute, thus rendering it of
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486 van nostrand's engineering magazine.
GEOLOGICAL COMMISSION OF BRAZIL,
PROFESSOR CH. FRED. HARTT, CHIEF.
One Volume, i8mo, boards. 175 pp. Price 50 cents. (Forming No. 37 Van Nostrand's Science
Series.)
GEOGRAPHICAL SURVEYING,
ITS USES, METHODS AND RESULTS,
BY
FRANK DE YEAUX CARPENTER, C. E.,
Geographer to the Cojnmission.
PEEFACE.
Charles Frederic Hartt, Professor of Geology in the Cornell University,
and Chief of the Geological Commission of Brazil, died on the eighteenth of March
last, in Rio de Janeiro, where he was engaged in preparing the reports of his Survey.
His death and the dissolution of the Commission, of which he was the founder
and director, have prevented the realization in Brazil of the plan of surveying pro-
posed in the accompanying pages.
F. D. Y. C.
New York, July, 1878.
LATE NUMBERS IN THE SERIES.
24. A Practical Treatise on the Teeth of Wheels, with the Theory and the Use of Robinson's
Odontograph. By S. W. Robinson, Professor of Mechanical Engineering, Illinois Indus-
trial University. Illustrated.
25. On the Theory and Calculation of Continuous Bridges. By Mansfield Merriman, Ph. D.
Illustrated.
26. Practical Treatise on the Properties of Continuous Bridges. By Charles Bender, C. E.
Illustrated.
27. On Boiler Incrustation and Corrosion. By F. J. Rowan.
28. Transmission of Power by Wire Ropes. By Albert W. Stahl, U. S. N. Illustrated.
29. Steam Injectors ; Their Theory and Use. From the French of Leon Pochet.
30. The Magnetism of Iron Vessels, with a Short Treatise on Terrestrial Magnetism. By Fair-
man Rogers.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33. The Mechanics of Ventilation. By Geo. W. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon- Harcourt.
35. The Aneroid, and How to Use it. Compiled by George W. Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Maxwell.
Maximum Stresses in Framed Bridges. By Prof. Wm. Cain. {In Press.)
A Hand Book of the Electro-Magnetic Telegraph. By A. E. Loring. {In Press.)
Price, 50 Cents Each.
Z>. VJLJST NOSTRA.lsrZ>} JPiibUsher,
23 Murray and 27 Warren Streets, New York.
Copies sent by mail, postpaid, on receipt of price.
VAN NOSTRAND'S ENGINEERING MAGAZINE.. 487
-
New Number of the Science Series Just ready.
MAXIMUM STRESSES
IN
FRAMED BRIDGES.
BY
Prof. WM. CAIN, A.M., C.E.,
Author of a "Practical Theory of Voussoir Arches."
ILLUSTRATED.
PREFACE.
This treatise is clearly a proper supplement to the ordinary works on strains in
trusses. Every case of examination into causes of failure of broken structures
furnishes substantial evidence that such a treatise is an important addition to the
literature heretofore published.
The thoroughly practical character of all of Prof. Cain's literary works, and the
nattering reception of his previous work ( Voussoir Arches) by working engineeers,
have induced the publisher to reprint these recent contributions to the Magazine in
the Science Series.
LATE NUMBERS IN THE SERIES.
24. A Practical Treatise on the Teeth of Wheels, with the Theory and Use of Robinson's
Odontograph. By S. W. Robinson, Professor of Mechanical Engineering, Illinois Indus-
trial University. Illustrated.
25. On the Theory and Calculation of Continuous Bridges. By Mansfield Merriman, Ph. D.
Illustrated.
26. Practical Treatise on the Properties of Continuous Bridges. By Charles Bender, C. E.
Illustrated.
27. On Boiler Incrustation and Corrosion. By F. J. Rowan.
28. Transmission of Power by Wire Ropes. By Albert W. Stahl, U. S. N. Illustrated.
29. Steam Injectors ; Their Theory and Use. From the French of Leon Pochet.
30. The Magnetism of Iron Vessels, with a Short Treatise on Terrestrial Magnetism. By Fair-
man Rogers.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the Construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33. The Mechanics of Ventilation. By Geo. W. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon-Harcourt.
35. The Aneroid, and How to Use it. Compiled by George W. Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Maxwell.
37. Geographical Surveying, its Uses, Methods, and Results. By Frank De Yeaux Carpenter.
39. A Hand Book of the Electro-Magnetic Telegraph. By A. E. Loring. {In Press.)
Price 50 Cents Each.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Streets, New York,
*** Copies sent by mail, post paid, on receipt of price.
488
VAN NOSTRAND'S ENGINEERING MAGAZINE.
One Volume, 8vo, 180 pp., illustrated. New, revised and enlarged edition.
Cloth, $1.50.
MANUAL OF
I
FOR THE USE OF STUDENTS IN COLLEGES AND
NORMAL AND HIGH SCHOOLS,
BY
GEO. C. CALDWELL, S. B., Ph. D.,
Professor of Agricultural and A nalytical Chemistry
AND
ABRAM A. BRENEMAN, S. B.,
Assistant Professor of Applied Chemistry.
IN CORNELL UNIVERSITY.
SECOND EDITION, REVISED AND CORRECTED
EXTRACT FROM PREFACE TO FIRST EDITION.
This work is the result of a preliminary trial made with a class in the chemical
laboratory of Cornell University in the Fall term of 1874. A small part of the
matter contained in it was printed then in detached sheets for the use of the
students. The work will be found on examination to present a mode of chemical
practice which has the merit at least of novelty, and the experience of the authors
justifies their expectations that it will be found to possess the more important merit
of efficiency.
D. VAN NOSTBAND, Publisher,
23 Murray and 27 Warren Streets, New York,
"V^Copies sent free by mail on receipt of price.
VAN XOSTRAND'S ENGINEERING MAGAZINE.
573
BEST LITERATURE OF THE MY."-iV. Y. Times.
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ter, Frances Power Cobbe,
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Donald, Miss Oliphant,
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THE
f
attei^n Maker's Assistant
«
EMBRACING LATHE WORK, BRANCH WORK, CORE WORK,
SWEEP WORK, AND
PRACTICAL GEAR CONSTRUCTION;
^Preparation, and TJ"se of" Tools;
TOGETHER WITH A LARGE COLLECTION OF
USEFUL AND VALUABLE TABLES.
BY
JOSHUA ROSE, M. E.,
AUTHOR OF "COMPLETE PRACTICAL MACHINIST."
COITTEITTS.
Chapter I. — General Remarks ; Selection of Wood ; Warping of Wood ; Drying of Wood ;
Plane-irons ; Grinding Plane-irons ; Descriptions of Planes ; Chisels ; Gouges ; Compasses ; Squares ;
Gages; Trammels; Winding-strips; Screw -d river ; Mallet; Calipers. Chapter II. — Lathe;
Lathe Hand-rest ; Lathe Head; Lathe Tail-stock ; Lathe Fork; Lathe Chucks; Gouge; Skew-
chisel ; Turning Tools. Chapter III. — Molding Flask ; How a Pattern is Molded ; Snap Flask.
Chapter IV. — Description of Cores ; Core-boxes ; Examples of Cores; Swept Core for Pipes, etc.
Chapter V. — Solid Gland Pattern ; Molding Solid Gland Pattern; Gland Pattern without Core-
print ; Gland Pattern made in Halves ; Bearing or Brass Pattern ; Rapping Patterns ; Example in
Turning ; Sand-papering ; Pattern Pegs ; Pattern Dog, or Staple ; Varnishing ; Hexagon Gage ;
Scriber. Chapter VI. — Example in T -joints, or Branch Pipes ; Example in Angular Branch Pipes ;
Core Box for Branch Pipes. Chapter VII.— Double-flanged Pulley; Molding Double-flange
Pulley; Building up Patterns; Shooting-board; Jointing Spokes. Chapter VIII. — Pipe Bend;
Core-Box for pipe Bend ; Swept Core for Pipe Bend ; Staving or Lagging ; Lagging Steam
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Chapter XIV. — Gar- wheels ; Construction of Pinion ; Construction of Wheel-teeth ; Gage for
. Wheel- teeth ; Bevel Wheels; Building up Bevel -wheels ; Worm Patterns; Turning Screw of
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for Hydraulic Presses • Calculating Rims of Fl**- wheels.
D. VAN NOSTRAND, Publisher,
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Submarine Warfare,
OFFENSIVE AND DEFENSIVE,
Including a Discussion of the
OFFENSIVE TORPEDO SYSTEM,
Its Effects upon Iron-Clad Ship Systems, and Influence upon
Future Naval Wars.
BY
LT. COM. J. S. BARNES, U. S. N
PREFACE.
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there is much therein open to adverse criticism, and feels very confident that it will
not be spared, particularly by his professional brethren of both branches of the
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Destruction of the Housatonic — Fulton's Torpedoes — Fulton's Torpedo Boats —
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Contact Torpedo Fuzes — Rebel Buoyant Torpedoes — Rebel Current Torpedoes
and Circumventers — Rebel Hydrogen Gas Current, Clock and Coal Torpedoes —
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Ericsson's Torpedo and Igniting Apparatus — Major King's Theories of Explosions
— Wheatstone's Magneto-Electric Battery.
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VAN NOSTRAND'S ENGINEERING MAGAZINE. 579
No. 39 of"tlie Science Series now ready.
A. VALUABLE ADDITION.
A HAND-BOOK
OF THE
ELECTRO MAGNETIC
TELEGRAPH.
-A~ IE. LOBINQ,
A Practical Telfgkaphek.
INTRODUCTION.
It has been the aim of the author in the preparation of this little book, to present the principles
of the Electro Magnetic Telegraph, in a brief, concise manner, for the benefit of practical
operators and students of telegraphy. The works on telegraphy which have thus far been
presented, besides being expensive, have contained much that is useless, or which is not in a form to
be readily understood by young and inexperienced telegraphers. Although this little work must be
acknowledged incomplete, it is hoped that it may go far toward supplying the deficiency which has
existed ; or, at least, serve as a stepping-stone to the study of the more complete works on electricity
and telegraphy.
_ THE AUTHOR.
0 CONTENTS.
Part I.— Electricity and Magnetism. -Electricity— Positive and Negative. Conductors and Non-Conductors.
Galvanic Batteries. Galvanic Circuits. Electrical Quantity and Intensity. Resistance. Electro-Motive"
Force. Haskin's Galvanometer and its Uses. Ohms Law. Measurement of Currents. Measurement of
Resistance. Speed of the Current. Divided Circuits. Electro-Magnets. Residual Magnetism. Proportion
of Electro-Magnets to Circuits. Intensity and Quantity Magnets.
Part II.— The Morse Telegraph.— Fundamental Principle. Telegraph Circuits. Intermediate offices. The
Local Circuit. Ground Wires. The Key. The Relay. The Sounder. Main Line Sounders. The Box
Relay. Cut Outs. The Switch Board. Other Switches. Lightning Arresters. Loops. Arrangement of
Offices. Arrangement of Batteries. Repeaters.
Part III.— Batteries. — Grove Battery. Carbon Battery. Amalgamation of Zincs. Daniell Battery. Hill
Battery. Other Forms of Battery. Battery Insulators.
Part IV.— Practical Telegraphy.— Alphabet and Numerals. Adjustment of Instruments. Testing Telegraph
Lines. Breaks. Escapes. Grounds. Crosses.
Part V.— Construction of Lines.— The Conductors. The Insulators. Fitting up Offices. Ground Wire
Connections. Private and Short Lines.
Appendix.— Suggestions and Exercises for Learners.
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LATE NUMBERS IN THE SERIES.
31. The Sanitary Condition of City and Country Dwelling Houses. By Geo. E. Waring, Jr.
32. Cable Making for Suspension Bridges, as exemplified in the Construction of the East River
Bridge. By Wilhelm Hildenbrand, C. E. Illustrated.
33. The Mechanics of Ventilation. By Geo. VV. Rafter, C. E.
34. Foundations. By Jules Gaudard. Translated from the French by L. F. Vernon- Harcourt.
Illustrated.
35. The Aneroid, and How to Use it. Compiled by Geo. W. Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Maxwell.
37. Geographical Surveying, Its Uses, Methods and Results. By Frank De Yeaux Carpenter.
38. Maximum Stresses in Framed Bridges. By Prof. Wm. Cain. Illustrated.
40. Transmission of Power by Compressed Air. By Robert Zahner, M. E. (In Press).
41. On the Strength of Materials. By Wm. Kent, M. E. (In Press).
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580
VAN NOSTEAND'S ENGINEERING MAGAZINE.
1879.
Eclectic Magazine
OP
FOREIGN LITERATURE, SCIENCE, A1NI> ART.
TKivty-FtftK JTectr.
THE ECLECTIC MAGAZINE, now in its thirty-fifth year, reproduces from foreign
priodicals all those articles which, for any reason, are likely to prove interesting or
valuable to American readers. Its field of selection embraces all the leading foreign
Reviews, Magazines, and Journals; and covers a literature incomparably richer of its kind
than any other to which the reader can find access. As only the best articles of the several
periodicals are chosen, it is evident that the contents of the ECLECTIC must be more varied,
more valuable, and more interesting than those of any single review or magazine from which
its selections are made; and while the tastes of all classes of readers are consulted, nothing
trivial in character, or of merely transient interest, is admitted to its pages. Its plan includes
Essays, Reviews, Biographical Sketches, Historical Papers, Travels,
Poetry, Novels, and Short Stories ; and in the case of Science (to which much space
and attention are given), no special prominence is allowed to any particular phase of opinion,
but place is given impartially to the most valuable articles on both sides of the great themes
of scientific discussion.
The following lists comprise the principal periodicals from which selections are made and
the names of some of the leading writers who contribute to them :
PERIODICALS.
quarterly review.
British Quarterly Review,
Edinburgh Review.
Westminster Review.
Contemporary Review.
Fortnightly Review.
The Nineteenth Century.
Popular Science Review.
Blackwood's Magazine,
Cornhill Magazine.
Macmillan's Magazine.
Fraser's Magazine.
Temple Bar.
Belgravia.
Good Words.
Saturday Review.
The Spectator, etc, etc.
AUTHORS.
Right Hon. W. E. Gladstone.
Alfred Tennyson.
Professor Huxley.
Professor Tyndall.
Richard A. Proctor, B. A.
J. Norman Lockyer, F. R. S.
Dr. W. B. Carpenter.
E. B. Tylor.
Professor Max Muller.
Professor Owen.
Matthew Arnold.
Edward A. Freeman, D.C.L.
James Anthony Froude.
Thomas Hughes.
Anthony Trollope.
William Blagk.
Mrs. Oliphant.
turgenieff.
Miss Thackeray.
It is frequently remarked that in England the best literary talent of the time is being
diverted from the writing of books to contributing to the periodicals. The Eclectic garners the
choicest sheaves from this rich harvest.
STEEL ENGRAVINGS.
Each number contains a Fine Steel Engraving — usually a portrait — executed in the best
manner. These engravings are of permanent value, and add much to the attractiveness of
the Magazine.
TERMS: — Single copies, 45 cents; one copy, one year, $5; five copies, $20. Trial
subscription for three months, $1. The ECLECTIC and any $4 magazine to one address, $8.
Postage free to all subscribers.
B. B. PELTON, Publisher, 25 Bond St., New York.
JULY, 1878.
Number 115 Volume 19.
Van NostrancTs
ECLECTIC
GO
CD
CD
ENGINEERING I
CD
O
MAGAZINE. §
JULY, 1878
P
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CD
D. VAN NOSTBAND,
23 MURRAY STREET AND 27 WARREN STREET,
(up stairs.)
CONTENTS.
The Theory of Internal Stress in Graphical Statics.
By Henry T. Eddy, C. E., Ph. D., University of Cin-
cinnati. I. (Illustrated) Written for Van Noslrand's Magazine.. 1
The Modulus of Elasticity in some American Woods,
as Determined by Vibration. By Dr. Magnus C.
Ihlseng Written for Van Nostrand's Magazine. . 8
Circular Curves for Railways. By Prof. Wm, M.
Thornton, University of Virginia. (Illustrated) Written for Van NostranoVs Magazine. . 10
Ox the Cause of the Blisters on ' ' Blister Steel. r By
John Percy, M. D. , F. R S Journal of the Iron and Steel Institute . . 21
The Structural Provision for the Discharges of the
Rainfall of London The Builder 22
The Purification of Water. By Gustav Bischof , F.C. S. Journal of the Society of Arts 28
Gas as Fuel. By M. M. Pattison Muir Nature 39
Steam Engine Economy— a Uniform Basis for Compari-
son. By Charles E. Emery, M. E Trans. Amer. Soc. of Civil Engineers. . 42
Accurate Navigation. By Captain Miller The Nautical Magazine 47
Geographical Surveying. By Frank De Yeaux Carpen-
ter, C.E., Geographer to the Geological Commission of
Brazil Contrib. to Van Nostrandls Magazine. . . 52
Maximum Stresses in Framed Bridges. By Prof. Wm.
Cain, A.M. , C.E. I. (Illustrated) Contrib. to Van Nosirantfs Magazine. . 71
Space of Four Dimensions. By FredericK Zollner Trans, for Van Nosirand's Magazine. 83
Description of the Aubois Canal-Lock, Situated on
the Lateral Canal of the Loire River. By Prof.
William Watson, Ph. D., late U. S. Commissioner. (Il-
lustrated) Contrib. to Van Nostrand^s Magazine. . . 85
PARAGRAPHS.— The highest point reached by the Don Pedro Segundo Railway, 9; Importation of Glass Tumblers from
the United States, 41 ; The Moose Mine, in Colorado, 83.
REPORTS OF ENGINEERING SOCIETIES.— American Society of Civil Engineers ; Meeting of the American Institute
of Mining Engineers at Chattanooga; Engineers' Club of Philadelphia, 88 ; Institution of Mechanical Enginee s, 89.
IRON AND STEEL NOTES.— Preservation of Iron, 90; The Pig Iron Production of the United States, 91.
RAILWAY NOTES.— The East India Railway Company; Pioneer and Military Railways, 91 ; Steam Tramway Engines on
the Continent 93.
ENGINEERING STRUCTURES.— Long Span Railway Bridges, 93.
ORDNANCE AND NAVAL. — Torpedo Cases; Gun Carriages; Utilization or Discarded Breech-Loaders; Another Addition
to the British Navy, 93 ; Thames Torpedoes; Breech-Loadiug Artillery; A Collapsing Boat, 94:.
BOOK NOTICES.— Pine Plantations on the Sand Wastes of France, Compiled by John Croumbie Brown, LL. D.; The Jour-
nal of Forestry and Estates Management, 94 ; La Methode Graphique dans la Sciences Experimentales, Par E. J. Marey;
Traite Theorique et Pratique de la Fabrication du Sucre, Par E. J. Maumene, Tome II; Proceedings of the Institution of
Civil Engineers; The War Ships of Europe, by Chief Engineer King, United States Navy; The Road Master's Assistant
and Second Master's Guide, by William S. Huntington, Revised and Enlarged by Chas. Latimer; Boiler and Factory
Chimneys, by Robert Wilson, A.I.C.E., 95.
-MISCELLANEOUS.— Artificial Stone; Underground Telegraph Lines; Torpedo Defenses; Steel and Wrought Iron Projec-
tiles; The Storm Flood, 96.
Van Nostrand's Science Series.
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1- Chimneys for Furnaces, Fire Places
and Steam Boilers. By R. Armstrong, C. E.
2. Steam ifoile* Explosions. By Zerah
Colburn.
3- Practical Designing- of Retaining
Walls. By Arthur Jacob, A. B. With Illustrations.
4. Proportions of Pins used in Bridges.
By Charles E. Bender, C. E. With Illustrations.
5. Ventilation of Buildings. By W. F. But-
ler. With Illustrations.
6. On the Designing and Construction
of Storage Reservoirs. By Arthur Jacob. With
Illustrations.
7. Surcharged and Different Forms of
Retaining Walls. By James S. Tate, C. E.
8. A Treatise on the Compound Engine.
By John Turnbull. With Illustrations.
9. Fuel. By C. William Siemens, to which is ap
pended the value of Artificial Fuels as compared with coal.
By John Wormald, C. E.
10. Compound Engines. Translated from the
French by A. Mallet. Illustrated.
11. Theory of Arches. By Prof. W. Allan, of
the Washington and Lee College. Illustrated.
12. A Practical Theory of Voussoir
Arches. By William Cain, C. E. Illustrated.
13. A Practical Treatise on the Gases
met with in Coal Mines. By the late J. J. Atkin-
son, Government Inspector of Mines for the County of Dur-
ham, England.
Friction of Air in Mines. By J. J. At-
kinson, author of "A Practical Treatise on the Gases met
with in Coal Mines."
15. Skew Arches. By Prof. E. W. Hyde, C. E.
Illustrated with numerous engravings and 3 folded plates.
16. A Graphic Method for Solving Cer-
tain Algebraical Equations. By Prof. George j
L. Vose. With Illustrations.
17. Water and Water Supply. By Prof.
W. H. Corfield, M. A., of the University College, London.
18. Sewerage and Sewage Utilization.
By Prof. W. H. Corfield, M. A., of the University College,
London.
19. Strength of Beams Under Trans-
verse Loads. By Prof. W. Allan, author of " Theory
of Arches." With Illustrations.
20. Bridge and Tunnel Centers. By John
B. McMasters, C. E. With Illustrations.
21. Safety Valves. By Richard H. Buel, C. E.
With Illustrations.
22. High Masonry Dams. By John B.
McMasters, C. E. With Illustrations.
23. The Fatigue of Metals under Repeated
Strains, with Tables of Results of Experiments. From the
German of Prof. Ludwig Spangenberg. With a Preface by
S. H. Shreeve, A. M. With Illustrations.
24. A Practical Treatise on the Teeth
Of Wheels, with the theory of the use of Robinson's
Odontograph. By S. W. Robinson, Professor of Mechani-
cal Engineering, Illinois Industrial University. With
Illustrations.
25* Theory and Calculations of Contin-
uous Bridges. By Mansfield Merriman, C. E. With
Illustrations.
26. Practical Treatise on the Proper-
ties of Continuous Bridges. By Charles
Bender, C. E. With Illustrations.
27. On Boiler Incrustation and Corro-
sion. By F. J. Rowan. With Illustrations.
28. On Transmission of Power by Wire
Rope. By Albert W. Stahl. With Illustrations.
29. Injectors. Their Theory and Use. Trans-
lated from the French of M. Leon Pouchet, With Illustra-
tions.
30. Terrestrial Magnetism and the
Magnetism of Iron Ships. By Prof. Fairman
Rogers. With Illustrations.
31. The Sanitary Condition of Dwelling
Houses in Town and Country. By George E
Waring, Jr. With Illustrations.
32. Cable Making for Suspension Brid-
ges as Exemplified in the Fast River
Bridge. By Wilhelm Hildenbrand, C. E. With Illus-
trations.
33. Mechanics of Ventilation. By George
W. Rafter, Civil Engineer.
34. Foundations. By Prof. Jules Gaudard, C.E.
Translated from the French, by L. F. Vernon Harcourt,
M.I.C.E.
35. The Aneroid Barometer, Its Con-
struction and Use. Compiled by Prof. George W.
Plympton. Illustrated
36. Matter and Motion. By J. Clark Ma-
well, M. A.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Sts., Neiv York
*#* Copies sent free by mail on receipt of price.
VAN NOSTRAND'S
COMMENCED JANUARY, 1869.
Consists of Articles selected and matter condensed from all the Engineering
Serial Publications of Europe and America, together with original articles.
The Eighteenth volume of this magazine was completed by the issue for June.
The growing success during the past eight years demonstrates the correctness of
the theory upon which the enterprise was founded. Communications from many
sources prove that the magazine has met a wide-spread want among the members of
the engineering profession.
A summary of scientific intelligence, selected and sifted from the great list of
American and European scientific journals, is at present afforded by no other means
than through the pages of this magazine.
It is designed that each number of the Magazine shall contain some valuable
original contribution to Engineering literature. Each number of the Magazine will
hereafter contain something of value relating to each of the great departments of
engineering labor.
More space than heretofore will be devoted to short discussions or elucidations
ol important formula?, especially such as have proved valuable in the practice of
working engineers ; our facilities for affording such items are extensive and rapidly
increasing.
The progress of great engineering works in this country will be duly chronicJed
Selected and condensed articles, with their illustrations, from English, French,
trerman, Austrian, and American scientific periodicals, will contribute to make this
Magazine more than ever valuable to the engineering profession, and will afford a
compilation without which the library of the working engineer will be incomplete
Cloth covers for Volumes I. to XVIII. inclusive, elegantly stamped in gilt, will
be furnished by the Publisher, for fifty cents each.
If the back numbers be sent, the volumes will be bound neatly in black cloth and lettered,
for seventy -five cents each. The expense of carriage must be borne by the subscriber.
Notice to New Subscribers. — Persons commencing their subscriptions with the Nineteenth'
Volume (July, 1878), and who are desirous of possessing the work from its commencement, will be supplied
with Volumes I. to XVIII. inclusive, neatly bound in cloth, for $48.00; in half morocco, $74.50— sent
by mail on receipt of price.
Notice to Clubs. — An extra copy will be supplied gratis to every Club of Five subscribers
)Iiea
AUUUUT, 1878.
Number 116 Volume 19.
Van Nostrand's
ECLECTIC
ENGINEERING
MAGAZINE.
AUGUST, 1878.
D. VAN NOSTRAlNnD,
23 MURRAY STREET AND 27 WARREN STREET,
(up stairs.)
CONTENTS.
PAGE.
The Theory op Internal Stress in Graphical Statics.
By Henry T. Eddy, C. E., Ph. D., University of Cin-
cinnati. II. (Illustrated) Written for Van Nostrands Magazine.. 97
Street-Cleansing in Paris. By M. Vaissiere Annales des Ponts et Chaussees 103
Iron and Steel for Shipbuilding, &c. By W. W. Kid-
dle, A. I. C. E The Nautical Magazine 105
The Drainage System of Glasgow The Engineer 112
Apparatus to Measure Directly the Strain to Which
the Pieces of an Iron Lattice Girder are Exposed.
By Prof. William Watson, Ph. D., late U. S. Commis-
sioner. (Illustrated) Contrib. to Van Nostrand's Magazine. . . 115
On Steam Boiler Explosions, and Experiments in Rela-
tion Thereto. By Dr. Herman Schemer Organ fur die Fortschritte des Eisenbahn-
wesens 119
Influence of the Moon on the Earth's Magnetism.
By John Allan Broun Nature 121
The Sewage System of Paris Engineering 124
Japanese Methods of Protecting the Banks of Rivers.
By W. S. Chaplin. (Illustrated) Written for Van Nostrands Magazine. . 129
The Transmission of Motion to a Distance by Means of
Electricity. By M. Cadiat, Engineer Trans, for Van Nostrands Magazine. 133
Wohler's Experiments on the Strength of Girders
After Repeated Concussions and Strains on Iron
Bridges. By Dr. E. Wrinkler, Professor of the Poly-
technic School at Vienna Foreign Abstracts of Inst, of Civil Eng. . 134
The Atmosphere Considered in its Geological Rela-
tions. By Edward T. Hardman, F.C.S., H.M. Geologi-
cal Survey of Ireland The Quarterly Journal of Science 135
Maximum Stresses in Framed Bridges. By Prof. Wm.
Cain, A.M., C.E. II. (Illustrated) Contrib. to Van Nostrands Magazine. . 146
Geographical Surveying. By Frank De Yeaux Carpen-
ter, C.E., Geographer to the Geological Commission of
Brazil. II Contrib. to Van Nostrands Magazine. . . 163
On the Present and Future Work of Engineers in
Reference to Public Health. By Mr. W. Donald-
son, M. A The Builder 183
PARAGRAPHS— Hardening Wood Pulleys, 114 ; Tests for Diamonds, 163.
REPORTS OF ENGINEERING SOCIETIES.— American Society of Civil Engineers, 185.
IRON AND STEEL NOTES.— Steel v. Iron, 185.
RAILWAY NOTES.— New Transportation Car ; Cheapest Railway in the World, 186.
ENGINEERING STRUCTURES.— A Great Engineering Feat, 187.
ORDNANCE AND NAVAL.— Monster Ordnance, 188 ; A New Piece of Heavy Ordnance; The Electric Fuse and Heavy
Cannon, 189 ; The Six-inch Armstrong Breech-loader ; Armor-plate Tests, 190.
BOOK NOTICES.— Elements of Descriptive Geometry, by J. B. Millar, B. E., 190 ; Metals and their Chief Industrial Ap-
plications, by Charles R. Alder Wright, D. Sc; Expose des Applications de l'Electricite, par Th. Du Moncel, Fifth
volume ; Water, Air and Disinfectants, by W. Noel Hartley, F.R.S.E., F.S.C ; Le Massif du Mont Blanc, Par E. Viollet-
le-Duc ; The Railway Builder, by Wm. J. Nicolls, Civil Engineer, 191.
MISCELLANEOUS.— New Air Duct for Mines ; Tide Calculating Machine for India ; Fire-resisting Flooring ; Telephone
Experiments in India, 193.
Van Nostrand's Science Series.
18mo, Fancy Boards, 50 Cents Each,
The subjects of this Series are of an eminently scientific character, and will
continue to embrace as wide a range of topics as possible.
1. Chimneys for Furnaces, Fire Places
and Steam Boilers. By R. Armstrong, C. E.
2. Steam Boiler Explosions. By Zerah
Colburn.
3- Practical Designing of Retaining
Walls. By Arthur Jacob, A. B. With Illustrations.
4. Proportions of Pins used in Bridges.
By Charles E. Bender, C. E. WithJUustrations.
5. Ventilation of Buildings. By W. F. But-
ler. With Illustrations.
6. On the Designing and Construction
of Storage Reservoirs. By Arthur Jacob. With
Illustrations.
7. Surcharged and Different Forms of
Retaining Walls. By James S. Tate, C. E.
8. A Treatise on thejCompound Engine.
By John Turnbull. With Illustrations.
9. Fuel. By C. William Siemens, to which is ap
pended the value of Artificial Fuels as compared with coal
By John Wormald, C. E.
10. Compound Engines. Translated from the
French by A. Mallet. Illustrated.
11. Theory of Arches. By Prof. W. Allan, of
the Washington and Lee College. Illustrated.
12. A Practical Theory of Voussoir
Arches. By William Cain, C E. Illustrated.
13. A Practical Treatise on the Gases
met with in Coal mines. By the late J. J. Atkin-
son, Government Inspector of Mines for the County of Dur-
ham, England.
14. Friction of Air in Mines. By J. J. At-
| Vinson, author of* A Practical Treatise on the Gases met
with in Coal Mines."
15. Skew Arches. By Prof. E. W. Hyde, C. E.
Illustrated with numerous engravings and 3 folded plates
16. A Graphic Method for Solving Cer-
tain Algebraical Equations. By Prof. George
L. Vose. With Illustrations.
17. Water and Water Supply. By Prof.
W. H. Corfield, M. A., of the University College, London.
18. Sewerage and Sewage Utilization.
By Prof. W. H. Corfield, M. A., of the University College,
London.
19. Strength of Beams Under Trans-
verse Loads. By Prof. W. Allan, author of " Theory
of Arches." With Illustrations
20. Bridge and Tunnel Centers. By John
B. McMasters, C E. With Illustrations
21. Safety Valves. By Richard H. Buel, C. E.
With Illustrations.
22. High Masonry Dams. By John B.
j McMasters C. E. With Illustrations.
23. The Fatigue of Metals under Repeated
j Strains, with Tables of Results of Experiments. From the
German of Prof. Ludwig Spangenberg. With a Preface by
S. H. Shreve, A. M. With Illustrations.
24. A Practical Treatise on the Teeth
Of Wheels, with the theory of the use of Robinson's
Odontograph By S. W. Robinson, Professor of Mechani-
cal Engineering, Illinois Industrial University. With
Illustrations.
25* Theory and Calculations of Contin-
uous Bridges. By Mansfield Merriman, C. E. With
Illustrations.
26. Practical Treatise on the Proper-
ties of Continuous Bridges. By Charles
Bender, C E. With Illustrations.
27* On Boiler Incrustation and Corro-
sion. By F. J. Rowan. With Illustrations.
28. On Transmission of Power by Wire
Rope. By Albert W. Stahl. With Illustrations.
29. Injectors. Their Theory and Use. Trans-
lated from the French of M. Leon Pochet, With Illustra-
tions.
30. Terrestrial Magnetism and the
Magnetism of Iron Ships, By Prof. Fairman
Rogers. With Illustrations.
31. The Sanitary Condition of Dwelling
Houses in Town and Country. By George E.
Waring, Jr. With Illustrations.
32. Cable Making for Suspension Brid-
ges as Exemplified in the East River
Bridge. By Wilhelm Hildenbrand, C. E. With Illus-
trations.
33. Mechanics of Ventilation. By George
W. Rafter, Civil Engineer.
34. Foundations. By Prof. Jules Gaudard, C.E.
Translated from the French, by L. F. Vernon Harcourt,
M.I.C.E.
35. The Aneroid Barometer, Its Con-
struction and Use. Compiled by Prof. George W.
Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Max-
well, M. A.
37. Geographical Surveying. Its Uses,
Methods and Results. By Frank De Yeaux Carpenter, C.E.
38. Maximum Stresses In Framed
Bridges. By Prof. Wm. Cain, A. M., C. E.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Sts,, Netc York
*#* Copies sent free by mail on receipt of price.
VAN NOSTRAND'S
COMMENCED JANUARY, 1869.
Consists of Articles selected and matter condensed from all the Engineering
Serial Publications of Europe and America, together with original articles.
The Eighteenth volume of this magazine was completed by the issue for June.
The growing success during the past eight years demonstrates the correctness of
the theory upon which the enterprise was founded. Communications from many'
sources prove that the magazine has met a wide-spread want among the members of
the engineering profession.
A summary of scientific intelligence, selected and sifted from the great list of
American and European scientific journals, is at present afforded by no other means
than through the pages of this magazine.
It is designed that each number of the Magazine shall contain some valuable
original contribution to Engineering literature. Each number of the Magazine will
hereafter contain something of value relating to each of the great departments of
engineering labor.
More space than heretofore will be devoted to short discussions or elucidations
ol important formula?, especially such as have proved valuable in the practice of
working engineers ; our facilities for affording such items are extensive and rapidly
increasing.
The progress of great engineering works in this country will be duly chronicled
Selected and condensed articles, with their illustrations, from English, FrendSj
German, Austrian, and American scientific periodicals, will contribute to make this
Magazine more than ever valuable to the engineering profession, and will afford a
compilation without which the library of the working engineer will be incomplete
Cloth covers for Volumes I. to XVIII. inclusive, elegantly stamped in gilt, wi]
be furnished by the Publisher, for fifty cents each.
If the back numbers be sent, the volumes will be bound neatly in black cloth and letterec
for seventy -five cents each. The expense of carriage must be borne by the subscriber.
Notice to New Subscribers. — Persons commencing their subscriptions with the Nineteenth,
Volume (July, 1878), and who are desirous of possessing the work from its commencement, will be supplie(
with Volumes I. to XVIII. inclusive, neatly bound in cloth, for $48.00; in half morocco, $74.50 — sent fre<
by mail on receipt of price.
**• Notice to Clubs. — An extra copy will be supplied gratis to every Club of Five subscribers
$5.00 each, sent in one remittance.
1.
SEPTEMBER, 1878.
Number 117 Volume 19.
Van Nostrand's
ECLECTIC
ENGINEERING
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SEPTEMBER , 1878 £0
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3D. VJ^N NOSTBAND,
23 MURRAY STREET AND 27 WARREN STREET,
(up stairs.)
CONTENTS
PAGE
A Project for the Permanent Improvement of the
Channel of Entrance into the Harbor of Charles-
ton, S. C, by Means of Low Jetties. By Q. A.
Gillmore, Lieut. -Col. Corps of Engineers, Bvt. Maj.
Gen. U. S. Army. (Illustrated.) Contrib. to Van Nostrand's Magazine. . . 193
Explosion of a Western River Steamer. By John W.
Hill, M. E. WHtten far Van Nostrand's Magazine. . 206
The Hydrology of the Mississippi River. Review of
Report by Humphreys and Abbot. By James B.
Eads, C. E (Illustrated) Written for Van Nostrand's Magazine. . 211
Momentum and Vis Viva. By S. Barnett, Jr Written for Van Noslrand's Magazine. . 229
Remabkable Changes in the Earth's Magnetism Nature 230
The Theory of Internal Stress in Graphical Statics.
By Henry T. Eddy, C. E., Ph. D., Uni yersity of Cin-
cinnati. HI. (Illustrated) • Written far Van Noslrand's Magazine.. 234
A Few Notes on Methods of Building, and Manufact-
ure of Materials, in India. By an Assistant Engineer,
D. P. W., Punjab The Builder 240
Food vs Fuel— Calculation of the Necessary Food for
a Horse at Work. By M. Bixio, President of the
Compagnie General des Voitures, Paris Trans, for Van Noslrand's Magazine. . 245
Buildings and Earthquakes Tlie Building News 248
The Action of Brakes English Mechanic 251
Iron as a Building Material The Architect 254
The Britannia Bridge The Engineer 256
Some Phenomena Exhibited by the Compass in Mining
Surveys. By William Lintern Engineering 259
Cleopatra's Needle and its Workmen The Builder 263
Problem for Rolling Stock and Railway Builders Iron 266
Steel Plates and Riveted Joints Engineering 268
Structures in an Earthquake Country. By John Perry
and W. E. Ayrton, Professors in the Imperial College of
Engineering, Tokio, Japan The Architect 271
Steel Ships The Nautical Magazine 274
The Brake as a Dynamometer The Engineer 277
PARAGRAPHS.— Telephones on the Central Pacific Railway, 333 ; Cheap House Protection from Lightning, 353 ; Experi-
ments on the Temperature of the Heat, 363.
REPORTS OF ENGINEERING SOCIETIES.— The Institution of Mechanical Engineers, 379.
IRON AND STEEL NOTES.— Analyses of Russian Iron ; The Classification of Iron and Steel at the Philadelphia
Exhibition; Siemens-Martin Metal Ruled to he Steel, 379.
RAILWAY NOTES.— The St. Gothard Railway; English and Native Fuel, as used in India, compared.; The Belgian
Grand Central Railway Co.; Railroads of the United States in 1S77, 380 ; On Bridging the Mississippi and Missourri
Rivers, 381.
ENGINEERING STRUCTURES.— Contemplated Improvement of Rivers in Brazil ; The Sutro Tunnel ; Foundations for
Bridges; Wire Tramway worked by Water Wheels 383 ; Public Works in France, 383.
ORDNANCE AND NAVAL.— New Gattling Guns, 383 ; The Loading of Heavy Guns ; A New Explosive ; A New
Italian Ironclad; The New Field Gun; Shell Penetration, 384 ; Quick Steaming; Torpedo Warfare, 385; Com-
posite Armor Plates, 386.
BOOK NOTICES.— Geographical Surveying: its Methods, Uses and results, by Frank Do Yeaux Carpenter; The Whit-
worth Papers. I, Plane Metallic Surfaces; II, An Uniform System of ScrewThreads ; III, A Standard Diurnal Measure
of Length, by Joseph Whitworth, Esq., Manchester ; Railway Service : Trains and Stations, by Marshall M. Kirkman ;
Proceedings of the Institution of Civil Engineers.— Excerpt Minutes, 387.
MISCELLANEOUS.— Source of Error in Leveling, 387 ; M. Bardoux, on Popular Education in Prance, 387 ; Failure of i
Supply of Ice in Bombay, 387 ; Le Neve Foster Testimonial Fund, 388 ; Disappearance of a Locomotive in the Quick-
sands of Kiowa Creek, Col., 388 ; Reorganization of the Paris Observatory, 388.
- ^— — — — .. :
Van Nostrand's Science Series.
18mo, Fancy Boards, 50 Cents Each,
The subjects of this Series are of an e?ninently scioitific character, and will
continue to embrace as wide a range of topics as possible.
I. Chimneys for Furnaces, Fire Places
and Steam Boilers. By R. Armstrong, C. E.
2- Steam Boiler Explosions. By Zerah
Colburn.
3. Practical Designing of Retaining.
Walls. By Arthur Jacob, A. B. With Illustrations.
4. Proportions of Pi ns used in Bridges.
By Charles E. Bender, C. E. With Illustrations.
5. Ventilation of Buildings. By W. F. But-
ler. With Illustrations.
6. On the Designing and Construction
of Storage Reservoirs. By Arthur Jacob. With
Illustrations.
7. Surcharged and Different Forms of
Retaining Walls. By James S. Tate, C. E.
8. A Treatise on the Compound Engine.
By John Turnbull. With Illustrations.
9. Fuel. By C. William Siemens, to which is ap
pended the value of Artificial Fuels as compared with coal
By John Wormald, C. E.
10. Compound Engines* Translated from the
French by A. Mallet. Illustrated.
II. Theory of Arches. By Prof. W. Allan, of
the Washington and Lee College. Illustrated.
12. A Practical Theory of Voussoir
Arches. By William Cain, C E. Illustrated.
13. A Practical Treatise on the Gases
met with in Coal Mines. By the late J. J. Atkin-
son, Government Inspector of Mines for the County of Dur-
ham, England.
14. Friction of Air in Mines. By J. J. At-
kinson, author of "A Practical Treatise on the Gases met
with in Coal Mines."
15. Skew Arches. By Prof. E. W. Hyde, C. E.
Illustrated with numerous engravings and 3 folded plates
16. A Graphic Method for Solving Cer-
tain Algebraical Equations. By Prof. George
L. Vose. With Illustrations.
17. Water and Water Supply. By Prof.
W. H. Corfield, M. A., of the University College, London.
18. Sewerage and Sewage Utilization.
By Prof. W. H. Corfield, M. A., of the University College,
London, •
19. Strength of Beams Under Trans-
verse Loads. By Prof. W. Allan, author of " Theory
of Arches." With Illustrations
20. Bridge and Tunnel Centers. By John
B. McMasters, C E. With Illustrations
By Richard H. Buel, C. E.
B.
21. Safety Valves,
With Illustrations.
22. High Masonry Dams. By John
McMasters C. E. With Illustrations.
23. The Fatigue of Metals under Repeated
Strains, with Tables of Results of Experiments. From the
German of Prof. Ludwig Spangenberg. With a Preface by
S. H. Shreve, A. M. With Illustrations.
24. A Practical Treatise on the Teeth
of Wheels, with the theory of the use of Robinson's
Odontograph By S. W. Robinson, Professor of Mechani-
cal Engineering, Illinois Industrial University. With
Illustrations.
25- Theory and Calculations of Contin-
uous Bridges. By Mansfield Merriman, C. E. With
Illustrations.
26. Practical Treatise on the Proper-
ties of Continuous Bridges. By Charles
Bender, C E. With Illustrations.
27. On Boiler Incrustation and Corro-
sion. By F. J. Rowan. With Illustrations.
28. On Transmission of Power hy Wire
Rope. By Albert W. Stahl. With Illustrations.
29. Injectors. Their Theory and Use. Trans-
lated from the French of M. Leon Pochet, With Illustra-
tions.
30. Terrestrial Magnetism and the
Magnetism of Iron Ships. By Prof. Fairman
Rogers. With Illustrations.
31. The Sanitary Condition of Dwelling
Houses in Town and Country. By George E.
Waring, Jr. With Illustrations.
32. Cable Making for Suspension Brid-
ges as Exemplified in the East River
Bridge. By Wilhelm Hildenbrand, C. E. With Illus-
trations.
33. Mechanics of Ventilation. By George
W. Rafter, Civil Engineer.
34. Foundations. By Prof. Jules Gaudard, C.E.
Translated from the French, by L. F. Vernon Harcourt,
M.I.C.E.
35. The Aneroid Barometer, Its Con-
struction and Use. Compiled by Prof. George W.
Plympton. Illustrated.
36. Matter and Motion. By J. Clerk Max-
well, M. A.
37. Geographical Surveying. Its Uses,
Methods and Results. By Frank De Yeaux Carpenter, C.E.
38. Maximum Stresses in Framed
Bridges. By Prof. Wm. Cain, A. M., C. E.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Sts., New York
*#* Copies sent free by mail on receipt of price.
VAN NOSTRAND'S
II
COMMENCED JANUARY, 1869.
Consists of Articles selected and matter condensed from all the Engineering
Serial Publications of Europe and America, together with original articles.
The Eighteenth volume of this magazine was completed by the issue for June.
The growing success during the past eight years demonstrates the correctness of
the theory upon which the enterprise was founded. Communications from many
sources prove that the magazine has met a wide-spread want among the members of
the engineering profession.
A summary of scientific intelligence, selected and sifted from the great list of
American and European scientific journals, is at present afforded by no other means
than through the pages of this magazine.
It is designed that each number of the Magazine shall contain some valuable
original contribution to Engineering literature. Each number of the Magazine will
hereafter contain something of value relating to each of the great departments of
engineering labor.
More space than heretofore will be devoted to short discussions or elucidations ■
ol important formulae, especially such as have proved valuable in the practice of
working engineers ; our facilities for affording such items are extensive and rapidly
increasing.
The progress of great engineering works in this country will be duly chronicled I
Selected and condensed articles, with their illustrations, from English, French,
German, Austrian, and American scientific periodicals, will contribute to make this
Magazine more than ever valuable to the engineering profession, and will afford a
compilation without which the library of the working engineer will be incomplete
Cloth covers for Volumes I. to XVIII. inclusive, elegantly stamped in gilt, will
be furnished by the Publisher, for fifty cents each.
If the back numbers be sent, the volumes will be bound neatly in black cloth and lettered,
for seventy -five cents each. The expense of carriage must be borne by the subscriber.
Notice to New Subscribers. — Persons commencing- their subscriptions with the Nineteenth i
Volume (July, 1878), and who are desirous of possessing the work from its commencement, will be supplied
with Volumes I. to XVIII. inclusive, neatly bound in cloth, for $48.00; in half morocco, $74.50 — sent free*
by mail on receipt of price.
OCTOBER, 1878.
Number 118 Volume 19.
Van Nostrand's
ECLECTIC
ENGINEERING
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MAGAZINE. g
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23 MURRAY STREET AND 27 WARREN STREET,
(up stairs.)
CONTENTS.
PAGE.
Maximum Stresses in Framed Bridges. By Prof. Wm.
Cain, A.M., C.E. III. (Illustrated) Contrib. to Van Nostrand's Magazine. . . 289
Uniformity in Sanitary Engineering The Engineer 308
A History of Deep Boring, or Earth Boring, as
Practised on the Continent. By Mr. J. Clark Jeffer-
son, A. R. S. M Paper read before Inst. ofMin. Engs. . . 310
Rapid Methods of Laying Out Gearing. By S. "W.
Robinson, Professor of Mechanical Engineering, Ohio
State University, formerly of the Illinois Industrial
University. (Illustrated.) Written for Van Nbstrand's Magazine. . 312
Tramways English Mechanic 318
Cotton Powder or Tonite The Engineer . 321
Artificial Marble The Building News 324
The Flow of Solids. By M. Henri Tresca, President of
the Societe des Ingenieurs Civils, Paris Engineering 326
The Action of Railway Brakes The Engineer 339
The River Thames Engineering 342
The Conservancy of Rivers and Streams. By Edward
Easton, Esq., President of the Section of Mechanical
Science Payer read before Sec. G of British Asso. 345
Brtcks and Brickmaking The Builder 353
A Method of Deducing Formulae from Experiments
on Wrought Iron Pillars. By John D. Crehore.
(Illustrated) Contrib. for Van Nostrand's Magazine.. 360
The Ventilation of Coal Mines. By George G. Andre. . Transactions of the Society of Engineers. 369
The Distribution of Ammonia. By Dr. R. Angus Smith,
F. R. S. , &c Journal of the Society of Arts 374
PARAGRAPHS.— M. H. Tresca elected President of the Societe des Ingenieurs, 317 ; Surrey of the Comstock Lode Silver
Mines 335 ; Donation towards the Building of the North Wing of University College, London, 338 ; Mosandria—
Another New Metal, 359 ; Sharpening Files, 368.
REPORTS OF ENGINEERING SOCIETIES.— American Society of Civil Engineers ; International Congress on Civil
Engineering, 377.
IRON AND STEEL NOTES.— Messrs. Hoopes & Townsend's Pamphlet, 377; Improvement in the Manufacture of Steel,
378 ; The Preservation of Iron Surfaces, 378.
RAILWAY NOTES.— Orenburg and Central Asia, 379 ; Victorian Railways, 379 ; A Half-Finished Railway, 379 ;
St. Gothard, 379.
ENGINEERING STRUCTURES.— The Suez Canal, 379 ; The New Eddystone Lighthouse, 379.
ORDNANCE AND NAVAL.— The Grarett Torpedo Boat, 381.
BOOK NOTICES.— Slide-Valve Gears, by Hugo Bilgram, M. E., Manual of Introductory Chemical Practice, by
Geo. C. Caldwell, S.B., Ph.D., and Abram A. Breneman, S.B., of Cornell University, Second Edition revised, 383 ;
Railroads— Their Origin and Problems, by Charles Francis Adams, Jr., Chemical Experimentation, by Samuel
P. Sad tier, A.M., Ph.D ; Annual Report of the Chief Signal Office to the Secretary of War for 1S7T; A Treatise on Files
and Rasps, by Nicholson File Company, Providence ; Van Nostrand's Science Series, No. 38, Maximum Stresses in
Framed Bridges, by Prof. Wm. Cain, A.M., C.E.; Manual of the Vertebrates of the Northern United States, Second
Edition, by David Starr Jordan, Ph.D.; The Life of John Fitch, by Thompson Westcott; Manual for Medical Officers
of Health, by Edward Smith, M.D., F.R.S., Second Edition, 383; L. Annee Scientifique et Industrielle, par Louis
Siguier ; Handbook of Inspectors of Nuisances, by Edward Smith, M.D., F.R.S. ; Food from the Far West, or Ameri-
can Agriculture, by James Macdonald ; Sanitary Engineering— A Guide to the Construction of Works of Sewerage and
House Drainage, by Baldwin Latham, F.G.S., C.E., Second Edition; Electric Lighting. A Practical Treatise, by
Hippolyte Fontaine, translated by Pajet Higgs, L.L.D. ; Oeuvres Completes de Laplace, New Edition ; Institution
of Civil Engineers, 384.
MISCELLANEOUS.— Rensselaer Polytechnic Institute, 384.
Van Nostrand's Science Series.
18mo, Fancy Boards, 50 Cents Each.
The subjects of this Series are of an eminently scientific character, and will
continue to embrace as wide a range of topics as possible.
I. Chimneys for Furnaces, Fire Places
and Steam Boilers. By R. Armstrong, C. E.
2* Steam Boiler Explosions. By Zerah
Colburn.
3> Practical Designing of Retaining
Walls. By Arthur Jacob, A. B. With Illustrations.
4. Proportions of Pius used in Bridges.
By Charles E. Bender, C. E. With.IUustrations.
5. Ventilation of Buildings. By W. F. But-
ler. With Illustrations.
6. On the Designing and Construction
Of Storage Reservoirs. By Arthur Jacob. With
Illustrations.
7. Surcharged and Different Forms of
Retaining Walls. By James S. Tate, C. E.
8. A Treatise on the Compound Engine.
By John Turnbull. With Illustrations.
9. Fuel. By C. William Siemens, to which is ap
pended the value of Artificial Fuels as compared with coal
By John Wormald, C. E.
10. Compound Engines- Translated from the
French by A. Mallet. Illustrated.
II. Theory of Arches. By Prof. W. Allan, of
the Washington and Lee College. Illustrated.
12. A Practical Theory of Voussoir
Arches. By William Cain, C E. Illustrated.
13. A Practical Treatise on the Gases
met with In Coal mines. By the late J. J. Atkin-
son, Government Inspector of Mines for the County of Dur-
ham, England.
14. Friction of Air in Mines. By J. J. At-
kinson, author of" A Practical Treatise on the Gases met
with in Coal Mines."
15. Skew Arches. By Prof. E. W. Hyde, C. E.
Illustrated with numerous engravings and 3 folded plates
16. A Graphic Method for Solving Cer-
tain Algebraical Equations. By Prof. George
L. Vose. With Illustrations.
IT. Water and Water Supply. By Prof.
W. H. Corfield, M. A., of the University College, London.
18. Sewerage and Sewage Utilization.
By Prof. W. H. Corfield, M. A., of the University College,
London.
19. Strength of Beams Under Trans-
verse Loads. By Prof. W. Allan, author of " Theory
of Arches." With Illustrations
20. Bridge and Tunnel Centers. By John
B. McMasters, C E. With Illustrations
21. Safety Valves. By Richard H. Buel, C. E.
With Illustrations.
22. High Masonry Dams. By John B.
McMasters. C. E. With Illustrations.
23. The Fatigue of Metals under Repeated
Strains, with Tables of Results of Experiments. From the
German of Prof. Ludwig Spangenberg. With a Preface by
, S. H. Shreve, A. M. With Illustrations.
24. A Practical Treatise on the Teeth
of Wheels, with the theory of the use of Robinson's
, Odontograph By S. W. Robinson, Professor of Mechani-
cal Engineering, Illinois Industrial University. With
j Illustrations.
25' Theory and Calculations of Contin-
{ UOUS Bridges. By Mansfield Merriman, C. E. With
I Illustrations.
26. Practical Treatise on the Proper-
j ties of Continuous Bridges. By Charles
Bender, C E. With Illustrations.
2T. On Boiler Incrustation and Corro-
sion. By F. J. Rowan. With Illustrations.
28. On Transmission of Power by Wire
Bope. By Albert W. Stahl. With Illustrations.
29. Injectors. Their Theory and Use. Trans-
lated from the French of M. Leon Pochet, With Illustra-
tions.
30. Terrestrial Magnetism and the
Magnetism of Iron Ships. By Prof. Fairman
Rogers. With Illustrations.
31. The Sanitary Condition of Dwelling
Houses i n Town aud Country. By George E.
Waring, Jr. With Illustrations.
32. Cable Making for Suspension Brid-
ges as Exemplified in the East River
Bridge. By Wilhelm Hildenbrand, C. E. With Illus-
trations.
33. Mechanics of Ventilation. By George
W. Rafter, Civil Engineer.
34. Foundations. By Prof. Jules Gaudard, C.E.
Translated from the French, by L. F. Vernon Harcourt,
M.I.C.E.
35. The Aneroid Barometer, its Con-
struction and Use. Compiled by Prof. George W.
Plympton. Illustrated
36. Matter and Motion. By J. Clerk Max-
well, M. A.
37. Geographical Surveying. Its Uses,
Methods and Results. By Frank De Yeaux Carpenter, C.E.
38. Maximum Stresses in Framed
Bridges. By Prof. Wm. Cain, A. M. . C. E.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Sts., New York
VAN NOSTRAND'S
COMMENCED JANUARY, 1869.
Consists of Articles selected and matter condensed from all the Engineering
Serial Publications of Europe and America, together with original articles.
The Eighteenth volume of this magazine was completed by the issue for June.
The growing success during the past eight years demonstrates the correctness of
the theory upon which the enterprise was founded. Communications from many
sources prove that the magazine has met a wide-spread want among the members of
the engineering profession.
A summary of scientific intelligence, selected and sifted from the great list of
American and European scientific journals, is at present afforded by no other means
than through the pages of this magazine.
It is designed that each number of the Magazine shall contain some valuabl
original contribution to Engineering literature. Each number of the Magazine wi]
hereafter contain something of value relating to each of the great departments o:
engineering labor.
More space than heretofore will be devoted to short discussions or elucidations!
ol important formula?, especially such as have proved valuable in the practice of
working engineers ; our facilities for affording such items are extensive and rapidly
increasing.
The progress of great engineering works in this country will be duly chronicled;
Selected and condensed articles, with their illustrations, from English, French,
trerman, Austrian, and American scientific periodicals, will contribute to make this
Magazine more than ever valuable to the engineering profession, and will afford a
compilation without which the library of the working engineer will be incomplete i
Cloth covers for Volumes I. to XVIII. inclusive, elegantly stamped in gilt, wil
be furnished by the Publisher, for fifty cents each.
If the back numbers be sent, the volumes will be bound neatly in black cloth and lettered
for seventy -five cents each. The expense of carriage must be borne by the subscriber.
Notice to New Subscribers. — Persons commencing their subscriptions with the Nineteenth
Volume (July, 1878), and who are desirous of possessing the work from its commencement, will be supplied!
with Volumes I. to XVIII. inclusive, neatly bound in cloth, for $48.00; in half morocco, $74.50 — sent free
by mail on receipt of price.
NOVEMBER, 1878.
Number 119 Volume 19.
Van Nostrand's
ECLECTIC
GO
CD
CD
ENGINEERING I
CD
O
MAGAZINE. %
NOVEMBER, 1878. P
CD
O
o
o
CD
$ew fort,
23 MURRAY STREET AND 27 WARREN STREET,
(up stairs.)
CONTENTS.
PAGE.
On the Proposed Removal of Smith's Island. By
Prof. Lewis M. Haupt. (Illustrated) Contrib. to Van Nostrand's Magazine. . . 385
Water Supply to a Stamp Mill in Venezuela, with
Notes on Kutter's Formula. By Wm, A. Biddle.
(Illustrated) Contrib. to Van NostrandCs Magazine.. . 390
Friction Between a Cord and Pulley. By I. O.
Baker Written for Van Nostrand's Magazine. . 395
The Ventilation of the Mont Cenis Tunnel. By
William Pole, F.R SS. L. and E., M. Inst. C.E Proceedings of Inst. Civil Engineers 396
The Determination of Rocks— Porphyry. By Melville
Atwood, F. G. S From Journal of Microscopy 399
Mathematical Science. Abstract of the Address of Mr.
Wm Spottiswoode to the British Association The Engineer 402
The Magnetic Needle — The Cause of its Secular
Variations. By Thomas Job, Utah Contrib. to Van]Nostrand's Magazine. . 413
The Programme of the Studies of the Architect
and of the Civil Engineer The Builder 419
Water Engines vs. Air Engines. By L. Trasenster, of
the University of Liege Translat. for Van NostrandCs Magazine. 424
The Most Ancient Land Survey in the World Tlie Building News 429
Apparatus for Determining the Resistance Offered
to Ships by Experiments on Their Models. By A.
Lettieri Rivista maritiima 432
Mechanical Conversion of Motion. By George Bruce
Halsted. (Illustrated) Contrib. to Van Nostrand's Magazine. . 433
On Aeronautics. By Richard Gerner, M. E Written for Van Nostra?id's Magazine. . 439
Transmission of Power by Compressed Air. By Robert
Zalmer, M. E. I. (Illustrated) Contrib. to Van Nostrand's Magazine. . 446
Recent Advances in the Manufacture of Iron and
Steel, as Illustrated in the Paris Exhibition. By
Richard Akerman, Professor at the School of Mines,
Stockholm The Engineer 459
PARAGRAPHS.— Drainage in Bombay, 418 ; Testing of Mr. Berthon's Twenty-eight Feet Collapsing Boats at Portsmouth,
4-33 ; Glycerine arrests Decomposition, 438 ; Arnold Hague, Mineralogist^going to China, 458.
REPORTS OF ENGINEERING SOCIETIES.— American Society of Civil Engineers ; Engineers' Club of Philadelphia, 471.
IRON AND STEEL NOTES.— Steel at the Paris Exhibition, 471 ; The Use of Steel for Structural Purposes ; The Mechani-
cal and other Properties of Iron and Mild Steel, 472.
RAILWAY NOTES.— Proposed Narrow-Gauge Railroad in Guatemala ; Dangerous Railway Shunting Operations ; Extension
of the Railway System in the Austro-Hungarian Empire; Statistics of Railway Employes in India, 473; Railway
Accidents ; Queensland Railways, 474.
ENGINEERING STRUCTURES.— Tunneling of the St. Gothard Railway ; The Altenburg Tunnel, 474.
ORDNANCE AND NAVAL.— Steam Steering Gear ; Russian Fast Sailing Steamers ; The Hecla, Torpedo Depot Ship ;
Steering of Screw Steamers, 475.
BOOK NOTICES.— Prang's Standard Alphabets, 476 ; A Practical Treatise on Casting and Founding, by N. E. Spretson;
Van Nostrand's Science Series, No. 39, A Hand Book of the Electro-Magnetic Telegraph, by A. E. LoriDg; Coal and
Iron in all Countries of the World, by J. Pechar ; A History of the Growth of the Steam Engine, by Robert H. Thurston,
AM., C.E.; The Analytical Theory of Heat, by Joseph Fourier, translated by Alexander Freeman, M.A., 477; Geo-
graphical Surveying, by Frank D. Yeaux Carpenter ; The Elements of Graphical Statics and their Applications to Framed
Structures, with Numerous Practical Examples of Cranes, Bridge, Roof and Suspension Trusses, etc., by A. Jay DuBois,
C.E., Ph.D.; A Handbook of Patent Law of All Countries, by William P. Thompson, C.E., 47 8.
MISCELLANEOUS.— Height of Jets; Glass-Cloth ; A New Method of Determining the Heat Value of Fuel; Confirmation of»
the Discover of the Planet Vulcan, 479; New Fire Engines ; Importance of Geological Knowledge to Engineers, 480.
Van Nostrand's Science Series.
18mo, Fancy Boards, 50 Cents Each*
The subjects of this Series are of an eminently scientific character, and will
continue to embrace as wide a range of topics as possible.
I. Chimneys for Furnaces, Fire Places
and Steam Boilers. By R. Armstrong, C. E.
2« Steam Boiler Explosions. By Zerah
Colburn.
3* Practical Designing of Retaining
Walls. By Arthur Jacob, A. B. With Illustrations.
4. Proportions of Pins used in Bridges.
By Charles E. Bender, C. E. Witttfllustrations.
5. Ventilation of Buildings. By W. F. But-
ler. With Illustrations.
6. On the Designing and Construction
Of Storage Beservoirs. By Arthur Jacob. With
Illustrations.
7. Surcharged and Different Forms of
Retaining Walls. By James S. Tate, C. E.
8. A Treatise on the Compound Engine.
By John Turnbull. With Illustrations.
9. Fuel. By C. William Siemens, to which is ap
•pended the value of Artificial Fuels as compared with coal
By John Wormald, C. E.
10. Compound Engines. Translated from the
French by A. Mallet. Illustrated.
I I . Theory of Arches. By Prof. W. Allan, of
the Washington and Lee College. Illustrated.
12. A Practical Theory of Voussoir
Arches. By William Cain, C E. Illustrated.
13. A Practical Treatise on the Gases
met with in Coal mines. By the late J. J. Atkin-
son, Government Inspector of Mines for the County of Dur-
ham, England.
14. Friction of Air in mines. By J. J. At-
kinson, author of "A Practical Treatise on the Gases met
with in Coal Mines."
15. Skew Arches. By Prof. E. W. Hyde, C. E.
Illustrated with numerous engravings and 3 folded plates
16. A Graphic method for Solving Cer-
tain Algebraical Equations. By Prof. George
L. Vose. With Illustrations.
17. Water and Water Supply. By Prof.
W. H. Corfield, M. A., of the University College, London.
IS. Sewerage and Sewage Utilization.
By Prof. W. H. Corfield, M. A., of the University College,
London.
19. Strength of Beams Under Trans-
verse Loads. By Prof. W. Allan, author of " Theory
of Arches." With Illustrations
20. Bridge and Tunnel Centers. By John
B. McMasters, C. E. With Illustrations
21. Safety Valves. By Richard H. Buel, C. E.
With Illustrations.
22. High masonry Dams. By John B.
McMasters C. E. With Illustrations.
23. The Fatigue of metals under Repeated
Strains, with Tables of Results of Experiments. From the
German of Prof. Ludwig Spangenberg. With a Preface by
S. H. Shreve, A. M. With Illustrations.
24. A Practical Treatise on the Teeth
Of Wheels, with the theory of the use of Robinson's
Odontograph By S. W. Robinson, Professor of Mechani-
cal Engineering, Illinois Industrial University. With
Illustrations.
25* Theory and Calculations of Contin-
uous Bridges. By Mansfield Merriman,C. E. With
Illustrations.
26. Practical Treatise on the Proper-
ties of Continuous Bridges. By Charles
Bender, C E. With Illustrations.
27. On Boiler Incrustation and Corro-
sion. By F. J. Rowan. With Illustrations.
28. On Transmission of Power by Wire
Bope. By Albert W. Stahl. With Illustrations.
29. Injectors. Their Theory and Use. Trans-
lated from the French of M. Leon Pochet, With Illustra-
tions.
30. Terrestrial magnetism and the
magnetism of Iron Ships. By Prof. Fairman
Rogers. With Illustrations.
31. The Sanitary Condition of Dwelling
Houses in Town and Country. By George E.
Waring, Jr. With Illustrations.
32. Cable making for Suspension Brid-
ges as Exemplified in the East Biver
Bridge. By Wilhelm Hildenbrand, C. E. With Illus-
trations.
33. mechanics of Ventilation. By George
W. Rafter, Civil Engineer.
34. Foundations. By Prof. Jules Gaudard, C.E.
Translated from the French, by L. F. Vernon Harcourt,
M.I.C.E.
35. The Aneroid Barometer, Its Con-
struction and Use. Compiled by Prof. George W.
Plympton. Illustrated.
36. matter and motion. By J. Clerk Max-
well, M. A.
37. Geographical Surveying. Its Uses,
Methods and Results. By Frank De Yeaux Carpenter, C.E.
3S. maximum Stresses in Framed
Bridges. By Prof. Win. Cain, A. M., C. E.
D. VAN NOSTRAND, Publisher,
23 Murray and 27 Warren Sts., New Jorfc
*** Copies sent free by mail on receipt of price.
VAN NOSTRAND'S
ECLECTIC fllBli MAGAZINE,
COMMENCED JANUARY, 1869.
Consists of Articles selected and matter condensed from all the Engineering
Serial Publications of Europe and America, together with original articles.
The Eighteenth volume of this magazine was completed by the issue for June.
The growing success during the past eight years demonstrates the correctness of
the theory upon which the enterprise was founded. Communications from many
sources prove that the magazine has met a wide-spread want among the members of
the engineering profession.
A summary of scientific intelligence, selected and sifted from the great list of
American and European scientific journals, is at present afforded by no other means
than through the pages of this magazine.
It is designed that each number of the Magazine shall contain some valuable
original contribution to Engineering literature. Each number of the Magazine will
hereafter contain something of value relating to each of the great departments of
engineering labor.
More space than heretofore will be devoted to short discussions or elucidations
ol important formulae, especially such as have proved valuable in the practice of
working engineers ; our facilities for affording such items are extensive and rapidly
increasing.
The progress of great engineering works in this country will be duly chronicled
Selected and condensed articles, with their illustrations, from English, French,
German, Austrian, and American scientific periodicals, will contribute to make this
Magazine more than ever valuable to the engineering profession, and will afford a
compilation without which the library of the working engineer will be incomplete
Cloth covers for Volumes I. to XVIII. inclusive, elegantly stamped in gilt, will
be furnished by the Publisher, for fifty cents each.
If the back numbers be sent, the volumes will be bound neatly in black cloth and lettered, i
for seventy -five cents each. The expense of carriage must be borne by the subscriber.
Notice to New Subscribers. — Persons commencing their subscriptions with the Nineteenth
Volume (July, 1878), and who are desirous of possessing the work from its commencement, will be supplied
with Volumes I. to XVIII. inclusive, neatly bound in cloth, for $48.00; in half morocco, $74.50— sent free 3
by mail on receipt of price.
"* Notice to Clubs. — An extra copy will be supplied gratis to every Club of Five subscribers at J
DECEMBER, 1878.
Number 120 Volume 1 9. „
Van Nostrand's
ECLECTIC
ENGINEERING
MAGAZINE.
DECEMBER, 1&7&,
•§m fork,
X). V^IST I^OSTR^lISJD,
23 MURRAY STREET AND 27 WARREN STREET,
(up stairs.)
CONTENTS.
PAGE.
Transmission of Power by Compressed Air. By Robert
Zahner, M. E. II. (Illustrated) Contrib. to Van Nostrand?s\ Magazine. .^481
Architectural Cements The Engineer * 498
The Origin op Metallurgy— The Bronze Age? From
the French of Emile Burnouf, by Christopher Fallon,
A.M , Translai. for Van Nostrand's Magazine. 502
The Co-Efficient of Friction from Experiments on
Railway Brakes. By Captain Douglas Galton, C.B.,
F.R.S., D.C.L From Journal of thelSoeiety of Arts 519
Experiments on the Heights, &c, of Jets from the
Hydrants of the Kingston Waterworks, Jamaica.
By Felix Target, Assoc. Inst. C.E. (Illustrated) Proceedings of Inst. Civil Engineers 524
The Prevention of Railway and Steamship Accidents.
By Professor Osborne Reynolds From Iron 526
The Rectangles that may he Inscribed in a Given
Rectangle. By Professor W. Allan. (Illustrated). . . WHtten for Van Nostrand's Magazine. . 532
On a New Method of Detecting Overstrain in Iron
and other Metals, and on its Application in the
Investigation of the Causes of Accidents to
Bridges and other Constructions. By Robert H.
Thurston, C.E. (Illustrated) Paper read before Amer. Soc. Civil Eng. 584
A New Graphical Construction for Determining the
Maximum .Stresses in the Wei; of a Bridge Truss.
By Ward Baldwin, University of Cincinnati. (Illustrated). Written for Van Xostrana"s\Magazine. . 588
On the Effect of River Improvement Works. By
James Dillon, Mem. Inst. C.E.I Engineering 541
On the Manufacture of Artificial Fuel. By E. F.
Loiseau Paper read before Amer. Inst.of Min. Eng. 544
On The Discharge of Sewage tnto Tidal Rivers. By
H. Law Engineering 548]
The Influence of Silicon on Cast Steel. By M.
Pourcel, of Terre Noire Iron 550
A Discussion of the Continuous Girder with Exam-
ples. By M. S. Hudgins. (Illustrated) Written for Van NostrancVs Magazine. . 533
On a New Dynamometer for Locomotives. By H.
Killiches Die Eisenbahn : 560]
The Use of Zinc in Steam Boilers Engineering 56l]
PARAGRAPHS.— Proposed International Industrial Exhibition in Glasgow in 1SS0, 531; Correction, 533; Bituminous]
coal discovered near Aurora, in Nevada, 537.
REPORTS OF ENGINEERING SOCIETIES.— American Society of Civil Engineers ; Engineers' Club of Philadelphia, 563 j
IRON AND STEEL NOTES.-Birmingham Wire Gauge ; Different Qualities of Iron and Steel, 564.
RAILWAY NOTES.— New Tram-Car Motor; Large Railway Wheels, 565; Origin of the Railway Ticket System; BoarJ
of Trade Reports on Railways of the United Kingdom ; Result of Railway Working in England in 1877 ; Chilled Cast
Iron Wheels, 56ft ; Project of a Railway across Newfoundland, 567.
ENGINEERING STRUCTURES.— Cost of Maintenance of Highways in and around Paris ; Wire Rope Conveyance, 567 j
Macadamized Roads, 568.
ORDNANCE AND NAVAL.— Telescopic Artillery Sights ; The Expenditure of Ammunition, 568.
Book Notices.— A Descriptive Treatise of Mathematical Drawing Instruments, Fifth Edition, by Wm. Ford Stanley ; Histoiro
Nationale de la Marine, Par Jules Trousset ; Handbook of Modern Chemistry ; .Organic and Inorganic, by Dr, Meymott
Tidy ; Experimental Researches in lure, Applied and Physical Chemistry, by E. Frankland, D.C.L., F.R.S.; The Artisan,:
by Robert Riddell ; Proceedings of the Institution of Civil Engineers, 569 ; Annual Report upon the Survey of the North-
ern and Northwestern Lakes, and the Mississippi River, in charge of Gen'l C. B. Comstock ; The Physical System of the
Universe— an Outline of Physiography, by Sydney B. J. Skertchly, F.G.S.; Examples of Modern Steam, Air and Gas En-
gines, by John Bourne, C.E. ; Dictionnaire de Chimie, Pure et Applicmee, Par Ad. Wurtz ; Report on Bridging of the*
River Mississippi between Saint Paul, Minn., and St. Louis, Mo., by Brevet Major General G. K. Warren, Major of En-
gineers, 570 ; Graphical Statics, by A. Jay DuBois, A communication from the authoi-, 571.
MISCELLANEOUS.— The Population of the Earth, 573,
INDEX TO VOL. XIX.
Van Nostrand's Science Series.
ISmOt Fancy Boards, 50 Cents Each,
The subjects of this Series are of an eminently scientific character, and will
continue to embrace as wide a range of topics as possible.
I. Chimneys for Furnaces, Fire Places
and Steam Boilers. By R. Armstrong, C. E.
2- Steam Boiler Explosions. By Zerah
Colburn.
3- Practical Designing of Retaining
Wall*. By Arthur Jacob, A. B. With Illustrations.
4. Proportions of Pins used in Bridges.
By Charles E. Bender, C. E. Withlllustrations.
.5. Ventilation of Buildings. By W. F. But-
ler. With Illustrations.
6. On the Designing and Construction
of Storage Reservoirs. By Arthur Jacob. With
Illustrations.
7. Surcharged and Different Forms of
Retaining Walls. By James s. Tate, C. E.
8. A Treatise on the Compound Engine.
By John Turnbull. With Illustrations.
9. Fuel. By C. William Siemens, to which is ap
pended the value of Artificial Fuels as compared with coal
By John Wormald, C. E.
10. Compound Engines. Translated from the
French by A. Mallet. Illustrated.
II. Theory of Arches. By Prof. W. Allan, of j
the Washington and Lee College. Illustrated.
12. A Practical Theory of Voussoir
Arches. By William Cain, C E. Illustrated.
13. A Practical Treatise on the Gases
met with ill Coal Klines. By the late J. J. Atkin-
son, Government Inspector of Mines for the County of Dur- |
ham, England.
14. Friction of Air in Klines. By J. J. At-
kinson, author of "A Practical Treatise on the Gases met
with in Coal Mines."
15. Skew Arches. By Prof. E. W. Hyde, C. E.
Illustrated with numerous engravings and 3 folded plates
16. A Graphic method for Solving Cer-
tain Algebraical Equations. By Prof. George
L. Vose. With Illustrations.
17. Water and Water Supply. By Prof.
W. H. Corfield, M. A., of the University College, London.
IS. Sewerage and Sewage Utilization.
By Prof. W. H. Coriield, M. A., of the University College,
London,
19. Strength of Reams Under Trans-
verse Loads. By Prof. W. Allan, author of " Theory
of Arches." With Illustrations
20. Bridge and Tunnel Centers. By John
B. McMasters, C. E. With Illustrations
21. Safety Valves. By Richard H. Buel, C. E.
With Illustrations.
22. High 'lasonry Dams. By John B.
McMasters C. E.' With Illustrations.
23. The Fatigue of Jletals under Repeated
Strains, with Tables of Results of Experiments. From the
German of Prof. Ludwig Spangenberg. With a Preface by
S. H. Shreve, A.M. With Illustrations.
24. A Practical Treatise on the Teeth
Of Wheels, with the theory of the use of Robinson's
Odontograph By S. W. Robinson, Professor of Mechani-
cal Engineering, Illinois Industrial University. With
Illustrations.
25* Theory and Calculations of Contin-
uous Bridges. By Mansfield Merriman.C. E. With
Illustrations.
26. Practical Treatise on the Proper-
ties of Continuous Bridges. By Charles
Bender, C. E. With Illustrations.
27. On Boiler Incrustation and Corro-
sion. By F. J. Rowan. With Illustrations.
28. On Transmission of Power by Wire
Rope. By Albert W. Stahl. With Illustrations.
29. Injectors. Their Theory and Use. Trans-
lated from the French of M. Leon Pochet, With Illustra-
tions.
30. Terrestrial Magnetism and the
Magnetism of Iron Ships. By Prof. Fairman
Rogers. With Illustrations.
31. The Sanitary Condition of Dwelling
Houses in Town and Country. By George E.
Waring, Jr. With Illustrations.
32. Cable flaking for Suspension Brid-
ges as Exemplified in the Fast River
Bridge. By Wilhelm Hildenbrand, C. E. With Illus-
trations.
33. Mechanics of Ventilation. By George
W. Rafter, Civil Engineer.
34. Foundations. By Prof. Jules Gaudard, C.E.
Translated from the French, by L. F. Vernon Harcourt,
M.I.C.K.
35. The Aneroid Barometer, Its Con-
struction and Use. Compiled by Prof. George W.
Plympton. Illustrated.
36. flatter and Motion. By J. Clerk Max-
well, M. A.
37. Geographical Surveying. Its Uses,
Methods and Results. By Frank De Yeaux Carpenter. C.E.
38. Maximum Stresses in Framed
Bridges. By Prof. Wm. Cain, A. M.. C. E.
D. VAN NOSTRAND, Publisher,
33 Mar ray and '17 Warren 8ts., New York
*** Copies sent free by mail on receipt of price.
VAN NOSTRAND'S
Engineering Magazine
COMMENCED JANUARY, 1869.
Published on the 15th of each month at $5.00 per year.
-♦-«♦»-*-
Consists of original contributions, and articles from the leading foreign
Engineering Journals.
The nineteenth volume is completed by the issue for December.
The growing success during the past ten years demonstrates the cor-
rectness of the theory upon which the enterprise was founded. Communi-
cations from many sources prove that the magazine has met a wide-spread
want among the members of the engineering profession.
A summary of scientific intelligence, selected and sifted from the great
list of American and European scientific journals, is at present afforded by
no other means than through the pages of this magazine.
It is designed that each number of the Magazine shall contain valuable
original contributions to Engineering literature, as well as something of
value relating to each of the great departments of engineering labor.
More space than heretofore will be devoted to short discussions or
elucidations of important formulae, especially such as have proved valuable
in the practice of working engineers ; our facilities for affording such items
are extensive and rapidly increasing.
The progress of great engineering works in this country will be duly
chronicled.
Selected and condensed articles from English, French, German,
Austrian, and American scientific periodicals, will contribute to make this
Magazine more than ever valuable to the engineering profession, and will
afford a compilation without which the library of the working engineer
will be incomplete.
Cloth covers for Volumes I. to XIX. inclusive, elegantly stamped in gilt,
will be furnished by the publisher, for fifty cents each.
If the back numbers be sent, the volumes will be bound neatly in black cloth
and lettered, for seventy-five cents each. The expense of carriage must be borne by
the subscriber.
Xotice to Itfew Subscribers. — Persons commencing their subscriptions with the
Twentieth Volume (January, 1879), and who are desirous of possessing the work from its com-
mencement, will be supplied with Volumes I. to XIX. inclusive, neatly bound in cloth, for $50.00.
in half morocco, $78.00.
Notice to Clubs. — An extra copy will be supplied gratis to every Club of Five subscribers
at $5.00 each, sent in one remittance.
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